Dissertations / Theses on the topic 'C-C bond cleavage'

Tot i que el camp de l'acoblament creuat ha desenvolupat increïbles avenços, la gran majoria de processos encara es basen en l'ús d'halurs d'aril. No obstant, aquest tipus d’electròfils presenten una toxicitat intrínseca i, al mateix temps, la seva síntesis resulta tediosa, especialment quan es tracta d'halurs d'aril altament funcionalitzats. A causa d'això, la comunitat sintètica s'ha bolcat en la recerca d'alternatives a l'ús d'halurs d'aril en química d'acoblament creuat. Grans esforços s'han desenvolupat en la última dècada per implementar els derivats del fenol en aquest tipus de transformacions a causa de l'abundància natural i comercial d'aquests compostos i a la seva baixa toxicitat en comparació amb els organohalurs. No obstant, l'alta energia d'activació necessària per trencar els enllaços C-O ha limitat considerablement l'ús de derivats de fenol en reaccions d’acoblament creuat, sobretot si es tracta d'éters de metil. Actualment la gran majoria de mètodes basats en aquesta família d’electròfils s'utilitzen en la formació d'enllaços C-C. Altrament, gairebé no existeixen tècniques per obtenir enllaços Cheteroàtom probablement a causa de la baixa reactivitat dels nucleòfils, on la densitat de càrrega negativa resideix en un heteroàtom. La present tesi doctoral s'ha centrat en el desenvolupament de noves metodologies per a la creació d'enllaços de tipus C-heteroàtom mitjançant l’activació catalítica d'enllaços C-O amb complexes de Ni. S'han descrit nous mètodes de sililació i borilació d'ésters i metil éters d’aril i benzil. Aquests mètodes suposen una via alternativa per a la síntesis de silans i boronats, els quals són intermedis de gran utilitat en síntesis orgànica. A més, el descobriment d'unes condicions totalment inusuals per activar enllaços de tipus C-OMe ha obert noves perspectives sobre la reactivitat d'aquest tipus d'enllaços i, alhora, ha suggerit l'existència de nous mecanismes d'activació.<br>A pesar de que el campo del acoplamiento cruzado ha desarrollado increíbles avances, la gran mayoría de procesos todavía se basa en el uso de halogenuros de arilo. Sin embargo, este tipo de electrófilos presentan una toxicidad intrínseca y, a su vez, su síntesis resulta tediosa, especialmente cuando se trata de halogenuros de arilo altamente funcionalizados. Debido a ello, la comunidad sintética se ha volcado en la búsqueda de alternativas al uso de halogenuros de arilo en química de acoplamiento cruzado. Un gran esfuerzo se ha desarrollado en la última década para implementar los derivados del fenol en este tipo de transformacions debido a la abundancia natural y comercial de dichos compuestos y a su baja toxicidad en comparación con los organohalogenuros. Sin embargo, la alta energía de activación necesaría para romper los enlaces C-O ha limitado considerablemenete el uso de derivados del fenol en reacciones de acomplamineto cruzado, sobre todo si se trata de éteres de metilo. Actualmente la gran mayoría de métodos basados en esta familia de electrófilos se utilizan en la formación de enlaces C-C. De lo contrario, apenas existen técnicas para obtener enlaces C-heteroátomo probablemente debido a la baja reactividad de los nucleófilos donde la densidad de carga negativa reside en un heteroátomo. La presente tesis docotoral se ha centrado en el desarrollo de nuevas metodologías para la creación de enlaces de tipo C-heteroatomo mediante la activción catalítica de enlaces C-O con complejos de Ni. Se han descrito novedosos métodos de sililación y borilación de ésteres y metil éteres de arilo y bencilo. Dichos métodos suponen una via alternativa para la síntesis de silanos y boronatos, los cuales son intermedios de gran utilidad en síntesis orgánica. Además, el descubrimiento de unas condiciones totalmente inusuales para activar enlaces de tipo C-OMe ha abierto nuevas perspectivas sobre la reactividad de este tipo de enlaces y, a la vez, ha sugerido la existencia de nuevos mecanismos de activación.<br>While the field of cross-coupling has reached remarkable levels of sophistication, the vast majority of processes are still being conducted with organic halide counterparts. Drawbacks associated to their toxicity and the limited accessibility of densely functionalized aryl halides have prompted chemists to develop powerful, yet practical, alternatives. Among these, the utilization of phenol derivatives as coupling partners via C-O bond cleavage would be particularly rewarding due to their readily availability and benign nature. However, the high activation energy required for effecting C–O bond cleavage has become a daunting challenge when devising catalytic techniques using phenol derivatives, specially always-elusive aryl methyl ethers. At present, the vast majority of cross-coupling reactions using phenol derivatives remains confined to C–C bond formation, whereas the formation of C-heteroatom bonds has been poorly studied, likely due to the less reactivity of heteroatom-based nucleophiles. This doctoral thesis has focused on the development of new methodologies for forging C-heteroatom bonds via Ni-catalyzed C-O bond cleavage. It has been described new protocols for the silylation and borylation of aryl and benzyl esters and methyl ethers. These methodologies can be used as useful alternatives towards the synthesis of aryl and benzyl silanes and boronates, incredible important intermediates in organic synthesis. Furthermore, the discovery of unusual, yet surprising, conditions for the cleavage of C-OMe bonds have opened up new vistas towards the reactivity of aryl and benzyl methyls ethers while suggesting new activation pathways.

La primera parte de la tesis se dedica al estudio del mecanismo de una reacción de activación C-H por un complejo de niobio. Se racionalizó el mecanismo de activación de enlaces C-H del benceno por el complejo TpMe2NbCH3(c-C3H5)(MeCCMe). El intermedio clave es un complejo inusual de 2-ciclopropeno. Conseguimos también racionalizar las selectividades obtenidas para la activación de varios alquilaromáticos por el complejo de niobio 2-ciclopropeno. También se investigó el papel del ligando alquino en estos complejos y su posible papel en procesos de migración de ligandos. En la segunda parte de la tesis, se investigaron las reacciones de acoplamiento cruzado con reactivos basados en silicio. Los resultados sugieren que la transmetalación es más fácil después de la disociación de la fosfina, o cuando un ligando bromuro está coordinado al paladio. El efecto beneficioso de la dibencilidenoacetona en el acoplamiento también fue aclarado.<br>The first part of the thesis is mainly devoted to the mechanism of a C-H activation reaction by a niobium complex. The mechanism of C-H bond activation of benzene by the TpMe2NbCH3-(c-C3H5)-(MeCCMe) complex was rationalized. The key intermediate is an unusual 2-cyclopropene complex. We rationalized the selectivities obtained for the activation of several alkylaromatics by the 2-cyclopropene niobium complex. The intriguing role of the alkyne ligand of the same complex, and its possible role in the migration processes, was investigated. In the second part of the thesis, we focused on the silicon based cross-coupling. The results suggest than the transmetalation is easier after phosphine dissociation, and in presence of the bromide ligand on the palladium. The beneficial effect of dibenzylideneacetone on the coupling was clarified.

The non-sustainable nature of fossil fuels as feedstocks for valuable chemicals, combined with the environmental damage caused by their extraction and combustion, increases the need for the development of a bio-based economy. While industry and public opinion are slowly shifting towards acceptance of this change, efficient technologies for the depolymerization and subsequent separation of lignocellulosic biomass fall short of the ever-increasing demand. In particular, there are currently no efficient, sustainable mass scale methods to convert lignin, the most abundant source of aromatic molecules on Earth. The use of oxovanadium(V) catalyst complexes to aerobically cleave C‒C bonds has been demonstrated previously and remains an attractive option for incorporation into a sustainable bio-based economy. Two new triphenoxyamine oxovanadium(V) catalysts with reduced steric bulk and electron density at the metal center (vs. previously reported complexes) have been synthesized for aerobic oxidative diol C‒C bond cleavage. These complexes were found to cleave less activated and more complex substrates than previous generations, including cyclic diols and polyalcohols. Several insights into the reaction pathways of this class of complex were elucidated through a series of kinetic studies. Experimentally, the rate of C‒C bond cleavage of both pinacol and hydrobenzoin was determined to be unaffected by substitution of the O‒H bonds with deuterium, suggesting that currently proposed mechanisms need to be revised. Multiple catalytic regimes were observed during anaerobic reaction, which were not altered significantly by the brief addition of O2. A series of density functional theory calculations revealed a plausible mechanism for the trialkoxy complex that did not involve a proton transfer in the rate determining step, instead suggesting that ligand-arm dissociation-reassociation play a significant role in the reaction. In a second project, new bisphenoxyamine-N-appended base ligand with less steric hindrance and electron density at the metal center, has been synthesized utilizing similar design principles gained from work with triphenoxyamine catalysts. When reacting with lignin model compound 1,2-diphenyl-2-methoxyethanol, this new complex displays a higher selectivity towards aldehydes and esters (relative to previous bisphenoxyamine-N-appended ligands), leading to a higher rate of C‒C bond cleavage. Investigations into the mechanism of bisphenoxy complexes, as well as the role of the N-appended base in reactivity, were performed using substrate pre-complexed bisphenoxy compounds. Thermolysis at 60 and 100 °C produced almost exclusively oxidative C‒H bond cleavage product benzyl methyl ether, with evidence for overoxidation product benzoic acid observed. Thermolysis of labelled substrate pre-complexed revealed that N-appended base may impede C‒C cleavage of 1,2-diphenyl-2-methoxyethanol by forcing the methyl ether away from the oxovanadium(V) center. Through the use of these multidentate phenoxyamine ligands, advances have been made towards sustainable oxovanadium catalysis in the pursuit of efficient and selective lignocellulosic disassembly for a sustainable bio-based economy.

The focus of this thesis is on C-O bonds activation by transition metal atoms. Lignin is a potential alternative energy resource, but currently is an underused biomass species because of its highly branched structure. To aid in better understanding this species, the oxidative cleavage of the Cβ-O bond in an archetypal arylglycerol β-aryl ether (β–O–4 Linkage) model compound of lignin with late 3d, 4d, and 5d metals was investigated. Methoxyethane was utilized as a model molecule to study the activation of the C-O bond. Binding enthalpies (ΔHb), enthalpy formations (ΔH) and activation enthalpies (ΔH‡) have been studied at 298K to learn the energetic properties in the C-O bond cleavage in methoxyethane. Density functional theory (DFT) has become a common choice for the transition metal containing systems. It is important to select suitable functionals for the target reactions, especially for systems with degeneracies that lead to static correlation effects. A set of 26 density functionals including eight GGA, six meta-GGA, six hybrid-GGA, and six hybrid-meta-GGA were applied in order to investigate the performance of different types of density functionals for transition metal catalyzed C-O bond cleavage. A CR-CCSD(T)/aug-cc-pVTZ was used to calibrate the performance of different density functionals.

This PhD thesis describes the use of vanadium(V) aminotriphenolate complexes VO-TPA(R,R’) as catalysts for aerobic oxidative cleavage of vicinal diols, β-O-4 lignin models and lignin itself. In Chapter 1 a general overview of the concept of biorefinery is given. In an ideal biorefinery, lignocellulosic biomass is transformed in order to obtain electric energy, biofuels (such as bioethanol) and fine chemicals. Among the lignocellulosic biomass fractions, lignin is considered the most earth-abundant renewable source of aromatic compounds, therefore, throughout the last few years researchers tried to develop more efficient depolymerization techniques. In particular, oxidative depolymerization should allow to obtain high value-added aromatic aldehydes (such as vanillin). With the purpose of finding a more efficient strategy for this process, in the research group in which this PhD thesis was carried out, VO-TPA(R,R’) complexes have been synthesized and already effectively employed as catalysts for oxidation reactions. In Chapter 2, the use of VO-TPA(R,R’) complexes as catalysts for aerobic C-C cleavage of vicinal diols is described. Meso-hydrobenzoin was chosen as a model substrate in order to elucidate the ligand, solvent and temperature effects to the reactivity/selectivity. The best reaction performances, in terms of TONs, TOFs and selectivity towards benzaldehyde formation were achieved using V5, bearing six chloro substituents on the ligand backbone, in toluene and O2 as oxidant. The reaction is quite general and effective with a large substrate scope, including tertiary, benzylic diols and also aliphatic linear and cyclic diols, obtaining in the majority of cases complete conversion towards the relative carbonyl compounds. Catalyst stability during the reaction course was verified by 1H-NMR and ESI-MS. Moreover, a reaction mechanism based on DFT calculation has been proposed. The reaction can be divided into three main steps: i. formation of a vanadium(V) non oxo-glycolate complex with formal elimination of a water molecule, ii. C-C bond cleavage of the substrate, with the formation of the relative carbonyl compounds by a two-fold electron transfer mechanism and generation of a V(III) species. iii. re-oxidization to V(V) by O2 via formation of V(IV)-peroxo-species. Noticeably, when increasing the reaction temperature (xylenes at 130°C), a change in selectivity towards the further oxidized benzoic acid was observed. We therefore investigated aerobic oxidation of both aromatic and aliphatic aldehydes using complex V5 as catalyst, collecting preliminary insights on the reaction mechanism. In Chapter 3, aerobic oxidative cleavage of non-phenolic and phenolic β-O-4 lignin models catalyzed by V5 is described. Differently from what found with 1,2-diols, the reaction occurs with different chemoselectivity affording products deriving from Cα-Cβ, Cβ-O and Cα-H cleavage (benzylic oxidation) mechanisms. The best catalytic performance was obtained using complex V5, in toluene under O2 (1 atm) with catalyst loadings down to 1%. The reaction selectivity is strongly oriented towards benzylic oxidation (Cα-H cleavage, 50-85 %), but at lower catalyst loadings (1 %), Cα-Cβ cleavage is favored with unprecedented high selectivity (up to 32%). These results were further confirmed with a non-phenolic trimeric model bearing two β-O-4 bonds (selectivity for Cα-H cleavage, 51-70 %, Cα-Cβ cleavage, 12-20 % and Cβ-O cleavage, 15-30 %). As regards phenolic β-O-4 models, reactions afford ketones deriving from benzylic oxidation as the major products (16-32 % yield), with a low degree of Cα-Cβ cleavage (2-5% yield). Finally, the importance of free benzylic -OH groups in order to have Cα-Cβ bond cleavage was highlighted, whereas the presence of free primary -OH group seems to assist the benzylic oxidation, leading to an enhancement of the selectivity towards ketones formation. In Chapter 4 the catalytic behavior of V5 was tested on lignin samples (wheat straw/sugarcane bagasse), the latter particularly rich in β-O-4 linkage motifs. Lignin samples (20 mg/mL) were treated with V5 (10% w/w) in dioxane or toluene at 100 °C, under O2 (1 atm). The course of the reaction was monitored by 2D-HSQC-NMR, GPC, MALDI-TOF-MS, 31P-NMR and FT-IR, analyses, showing a significative disappearance of β-O-4 linkages for both samples. In the case of SCB lignin, formation of the corresponding ketones (benzylic oxidation) was observed, whereas reaction with WS lignin yielded the highest degree of depolymerization, not only of β-O-4 linkages, but also of phenylcoumaran and resinol bonds. In conclusion, this PhD thesis reports the discovery of a new vanadium-based catalyst for effective C-C bond cleavage and lignin oxidative depolymerization, using molecular oxygen as terminal oxidant, in order to obtain valuable aromatic compounds starting from cheap and renewable sources.<br>Questo lavoro di tesi descrive l’utilizzo di complessi amminotrifenolati di Vanadio (V) VO-TPA(R,R’) come catalizzatori per la scissione ossidativa in ambiente aerobico di modelli del legame β-O-4 presente nella lignina e nella lignina stessa. Nel Capitolo 1 viene fornita una panoramica generale del concetto di bioraffineria dove, partendo dalla biomassa lignocellulosica, si possono ottenere energia elettrica, carburanti (bioetanolo) o fine chemicals. In particolare, la frazione ligninica della biomassa è considerata la sorgente rinnovabile più economica e disponibile di composti aromatici, pertanto in questi ultimi anni si sono cercate tecniche di depolimerizzazione sempre più efficienti. Tra le varie tecniche finora sviluppate, la depolimerizzazione ossidativa permette di ottenere aldeidi aromatiche ad elevato valore aggiunto (tra cui la vanillina). Con lo scopo di trovare una via catalitica più adatta per questo processo, nel gruppo di ricerca in cui è stata condotta questa tesi, sono stati sintetizzati i complessi VO-TPA(R,R’), già efficacemente impiegati come catalizzatori per reazioni di ossidazione. Nel Capitolo 2 viene descritto l’impiego dei complessi VO-TPA(R,R’) nella scissione ossidativa del legame C-C in dioli vicinali, usando il meso-idrobenzoino come modello per verificare l’effetto del legante, del solvente e della temperatura sulla reattività/selettività. Le migliori prestazioni in termini di TON e TOF, e selettività della reazione verso la benzaldeide, sono state ottenute con il complesso funzionalizzato con sei atomi di cloro nel legante V5, utilizzando toluene come solvente e sotto ossigeno (1 atm). Tale reazione è stata efficacemente impiegata in un’ampia classe di substrati, tra cui dioli terziari, benzilici, ma anche dioli alifatici lineari e ciclici, ottenendo nella maggior parte dei casi conversione completa nei relativi composti carbonilici. La stabilità del catalizzatore durante la reazione è stata verificata mediante 1H-NMR ed ESI-MS. È stato proposto inoltre un meccanismo di reazione basato su calcoli DFT. La reazione si può dividere in tre step principali: i. la formazione di un complesso non osso-glicolato di vanadio(V) con eliminazione formale di una molecola d’acqua, ii. la scissione C-C del substrato, con la formazione dei relativi composti carbonilici tramite un meccanismo di doppio trasferimento elettronico e la generazione di una specie di V(III), iii. la ri-ossidazione a V(V) da parte di O2 tramite la formazione di complessi perossidici di V(IV). Aumentando la temperatura di reazione (xilene a 130°C) è stato osservato un cambiamento nella selettività verso il prodotto di over-ossidazione acido benzoico. La reazione di ossidazione di aldeidi sia alifatiche che aromatiche è stata quindi investigata usando il complesso V5 come catalizzatore, raccogliendo risultati preliminari sul meccanismo di reazione. Nel Capitolo 3 viene descritta la scissione ossidativa di modelli non fenolici e fenolici di legame β-O-4 della lignina. A differenza di quanto osservato nel caso di dioli vicinali, la reazione decorre con diverse chemoselettività, portando alla formazione di prodotti derivanti da meccanismi di scissione Cα-Cβ, Cβ-O e Cα-H (ossidazione benzilica). La migliore attività catalitica è fornita dal complesso V5, in toluene sotto un’atmosfera di O2, con una concentrazione di catalizzatore inferiore all’1%. La selettività del sistema è fortemente diretta verso l’ossidazione benzilica (scissione Cα-H, 50-85 %), ma, abbassando la concentrazione di catalizzatore all’1%, si ottengono prodotti derivanti dalla scissione ossidativa Cα-Cβ con rese mai raggiunte da altri sistemi omogenei di V(V) (fino al 32 % di selettività). Questi risultati sono stati confermati anche con un modello trimerico non fenolico contenente due legami β-O-4 (selettività per la scissione Cα-H, 51-70 %, scissione Cα-Cβ, 12-20 % e scissione Cβ-O, 15-30 %). Per quanto riguarda invece i modelli fenolici, le reazioni portano a chetoni derivanti dall’ossidazione benzilica come prodotti maggioritari (16-32 % di resa), con una quantità minoritaria di prodotti derivanti dalla scissione Cα-Cβ (2-5 % di resa). Infine, è stata verificata l’importanza di gruppi -OH benzilici non funzionalizzati per avere scissione Cα-Cβ nei modelli, mentre la presenza di gruppi -OH primari non funzionalizzati sembra favorire l’ossidazione benzilica, aumentando la selettività della reazione verso la formazione di chetoni. Nel Capitolo 4, l’effetto catalitico dei complessi VO-TPA(R,R’) è stato verificato su campioni di lignina (paglia di grano/bagassa della canna da zucchero), quest’ultimo particolarmente ricco in legami β-O-4. I campioni di lignina (20 mg/mL) sono stati trattati con V5 (10 % m/m) in 1,4-diossano o toluene, a 100 °C usando O2 come ossidante terminale. Le reazioni sono state monitorate via 2D-HSQC-NMR, GPC, MALDI-TOF-MS, 31P-NMR e FT-IR, evidenziando una significativa scomparsa dei legami β-O-4 in entrambi i casi. Nel caso della lignina SCB, è stata osservata la formazione delle corrispondenti specie carboniliche (ossidazione benzilica), mentre dalla reazione della lignina WS si è ottenuto il più elevato grado di depolimerizzazione, non solo dei legami β-O-4, ma anche dei legami fenilcumarano e resinolo. In conclusione, questa tesi di dottorato riporta la scoperta di un nuovo catalizzatore a base di vanadio per la scissione del legame C-C e la depolimerizzazione ossidativa della lignina, usando ossigeno molecolare come ossidante terminale, in modo da ottenere composti aromatici di valore a partire da sorgenti rinnovabili ed economiche.

CO2 activation and conversion mediated by transition metal (TM) catalysts were investigated. Homogeneous catalysis of the reverse water gas shift reaction CO2+H2→H2O+CO was studied as a means to reduce CO2.  β-diketiminato metal models L'MI ( L' =C3N2H5-; M = first-row TMs) were considered as potential catalysts. The thermodynamics of prototypical reaction pathways were simulated using B3LYP/aug-cc-pVTZ. Results show that middle series metal complexes result in more thermodynamically favorable properties; therefore, more detailed thermodynamic and kinetic studies were carried out for Mn, Fe, and Co complexes. On the other hand, heterogeneous catalysis of the reduction of CO2 to CO was carried out on Fe, Co, Ni, and Cu surfaces, using the PBE functional. Reaction barriers were calculated using the climbing image nudged elastic band method. Late 3d and 4d transition metal ion (Fe, Co, Ni, Cu, Ru, Rh, Pd, and Ag) mediated activation of dimethyl ether was studied to investigate the intrinsic catalytic properties of metals for C-O bond cleavage. A set of density functional theory (DFT) methods (BLYP, B3LYP, M06, M06-L, B97-1, B97-D, TPSS, and PBE) with aug-cc-pVTZ basis sets was calibrated with CCSD(T)/CBS calculations on reaction energies and barriers.

Dans le cadre du développement durable, les procédés rapides, propres et peu énergivores sont très recherchés particulièrement en chimie pour les réactions d’oxydation. A part les solutions de génie des procédés, la catalyse est l’un des meilleurs atouts pour améliorer le processus. Le vanadium étant l’un des meilleurs métaux catalytiques pour de tels réactions, nous avions à nous attaquer son problème de relargage dans le milieu réactionnel en vue d’applications acceptables pour l’environnement. Nous proposons donc dans cette thèse des catalyseurs au vanadium fixé à l’intérieur des nano pores de silices mésoporeuses hexagonales de type MCM-41. La grande dispersion et la rétention du vanadium sont promues grâce à la présence d’ion d’ancrage : Al(III), Ti(IV), Zr(IV) and Ce(IV). Une grande variété de catalyseurs de type V-(Al/Ti/Zr/Ce)-MCM-41 ont été préparés à partir de trois méthodes de synthèse: l’une, ultra-rapide en une étape assistée par micro-onde, la seconde à étapes séquentielles multiples mettant en œuvre une technique de pochoir moléculaire et la troisième à nombre d’étapes réduites utilisant un traitement thermique partiel d’une surface préalablement organosilylée avant le greffage des métaux. Un large panel de techniques physicochimiques fut appliqué à la caractérisation de ces solides avec une attention particulière portée à l’analyse de la bande de transfert de charge ligand-métal du vanadium au degré d’oxydation +5 dont le décalage vers le bleu est corrélé à la taille des clusters d’oxyde de ces ions. La rétention du vanadium dans le méthanol a été corrélée à la dispersion du vanadium comme la dégradation à l’air du 1,2-diphényle-2-méthoxyéthanol. Ce substrat fut choisi comme modèle pour étudier la dégradation de la lignine par clivage C-C ou C-O. Notons que ce bio-polymère produit du phénoxypropanol methylé bio-sourcé utilisé dans les bio-carburants et comme précurseur en chimie fine. Dans le cas présent, un balayage à haut débit de la dégradation de cette molécule mettant en œuvre 96 mini-réacteurs en parallèle a permis de sélectionner le solvant, le métal d’ancrage et la teneure des deux métaux donnant la plus haute conversion. Contrairement aux catalyseurs homogènes, nos catalyseurs présentent une très haute sélectivité en clivage C-C<br>The search for practical large-scale, fast, clean and energy saving chemical processes are highly regarded in the frame of a sustainable development, particularly for the most problematic oxidation reactions. Apart from chemical engineering solutions, improving the process using heterogeneous catalysis is one of the most adapted solution. Vanadium being considered the best metal for such kind of reactions, one had to tackle the problem of its high dispersion on a support to minimize its high propensity for leaching and to optimize its stability for practicable, safe and clean uses. In the present thesis, vanadium is supported inside the nanopores of a mesoporous silica of MCM-41 type where the high dispersion is assisted by the presence of anchoring ions such as Al(III), Ti(IV), Zr(IV) and Ce(IV) ions. A large set of V-(Al/Ti/Zr/Ce)-MCM-41 catalysts was prepared according to three different methods of preparation: i) ultra-fast one-pot synthesis protocol using the assistance of microwave, ii) post-synthesis modification using molecular stencil patterning (MSP) technique and iii) partial thermal treatment (PTT) of the organo-silylated support. The catalysts were characterized thoroughly using a panel of physical techniques and, particularly, the blue shift of the optical gap measured from the vanadium charge transfer band known to correlated with the dispersion of the metal. In complement, the stability was tested from metal leaching using methanol as a corrosive solvent while their catalytic reactivity was estimated in the aerobic oxidation of 1,2-diphenyl-2-methoxyethanol. This is a model reaction that simulates the oxidative C-C bond cleavage in lignin, the most difficult and crucial step in the degradation of this biopolymer, then producing in a clean way valuable methoxylated phenoxy propanol units useful for biomass fuels or bio-sourced precursors for fine chemistry. A high throughput screening approach was applied to test this aerobic oxidation reaction running over 96 reactors in parallel at the same temperature and sorting out the best catalysts with the most suitable anchoring ions and metal loading for the highest catalytic efficiency<br>在可持续发展的背景下，对于清洁高效节能可行的大规模化工过程尤其是存在诸多问题的氧化反应过程的探索倍受瞩目。除化学工程解决方案之外，通过多相催化来改进反应过程也是最可行的途径之一。钒被认为是最适合于催化此类反应的金属之一，其亟待解决的问题是实现钒在载体上的高度分散，并最大限度地降低其浸出倾向，改善其稳定性，从而实现对其安全清洁有效的利用。本文提出将钒负载于MCM-41型六方介孔二氧化硅的纳米孔道中，通过锚定离子如Al(III)、 Ti(IV)、Zr(IV)、Ce(IV)离子的存在促进钒的高度分散和固载。采用三种不同的方法制备了一系列V-(Al/Ti/Zr/Ce)-MCM-41催化剂：1、超快微波一步合成法，2、使用分子复刻版技术改性的后嫁接法，3、对有机硅烷化载体进行部分热处理改性的后嫁接法。通过一系列物理化学技术对合成的催化剂进行了充分表征，特别是对与金属分散度相关的钒的电荷跃迁带的测量和与其对应的光谱带隙蓝移进行了分析。随后，以甲醇作为腐蚀溶剂对合成的钒催化剂进行了金属析出的稳定性测试。通过一种木质素模型化合物1,2-diphenyl-2-methoxyethanol的需氧氧化反应测试了所合成负载型钒催化剂的催化活性。在相同温度及反应条件下，用96通道高通量微反应器技术评价了所制催化剂对该反应的催化性能，筛选出具有最高催化效率的负载型钒催化剂及其最适合的锚定离子。该反应中的碳-碳键裂解反应是木质素降解的最关键也是最困难的步骤之一，可通过这类生物聚合物的降解以清洁的方式生产有用的生物质燃料或生物来源高附加值精细化学品前驱体。

En els darrers anys, la funcionalització catalítica d´enllaços C-C ha suscitat un gran interés, essent una de les disciplines amb més potencial en química organometàlica. Aquesta tesi doctoral es basa en el repte de dissenyar nous mètodes catalítics de functionalitazió d´enllaços C-C en anells de cuatre baules. Específicament, s´ha demostrat la viabilitat per preparar cetones γ-arilades via rotura d´enllaços C-C catalitzada per Pd en anells de tert-ciclobutanol utilitzant clorur d´aril i tosilats (Capítol 2). La transformació presenta una gran generalitat amb càrregues de catalitzador molt baixes. Tanmateix, s´ha trobat que fosfines riques en electrons i impedides estèricament permeten evitar processos destructius de β-eliminació d´hidrògen. Amb els precedents del capítol 2, s´ha extés satisfactòriament la generalitat de la reacció de rotura d´enllaços C-C d´anells de tert-ciclobutanol mitjançant l´acoplament amb haloacetilens per donar lloc a cetones amb grups alquins en posició γ (Capítol 3). Curiosament, els substituents del grup alquí tenen una gran influencia en la reacció. És certament remarkable l´interés potencial de la metodologia ja que els productes finals poden ser transformats fàcilment en productes d´alt valor afegit mitjançant reaccions d´acoplament creuat. Al Capítol 4, s´ha pogut extendre les metodologies de trencament d´enllaços C-C en anells de cuatre baules mitjançant el desenvolupament d´una metodologia catalitzada per Ni entre benzociclobutanones i diens per donar lloc a cicloadicions [4+4]. El mètode va mostrar una preferència específica per la formació d´anells de vuit baules respecte la formació d´anells de sis baules. Aquesta tesi doctoral també ha estudiat el disseny de metodologies de fixació de CO2 i formació d´enllaços C-F mitjançant activació catalítica d´enllaços C-C (Capítol 5). Tot i que no s´han trobat condicions de reacció òptimes, el nostre grup de recerca està actualment involucrat en el disseny de metodologies semblants i s´espera que aquesta recerca permeti el disseny de processos de fixació de CO2 i formació d´enllaços C-F mitjançant trencament C-C en un futur no molt llunyà.<br>Recientemente la funcionalización catalítica de enlaces C-C ha suscitado un gran interés en la comunidad científica a pesar de los retos que conlleva. Esta tesis doctoral se ha basado en diseñar nuevos procesos catalíticos para la funcionalización de enlaces C-C en anillos de cuatro miembros. Específicamente, se ha demostrado la viabilidad de preparar cetonas con grupos arilo en posición γ usando precatalizadores de Pd para promover la rotura de enlaces C-C en anillos de tert-ciclobutanol utilizando cloruros de arilo y tosilatos como agentes arilantes (Capítulo 2). La transformación se caracteriza por su amplia generalidad y baja carga de catalizador. La selectividad de la reacción puede ser fácilmente controlada por la naturaleza del ligando, en la que fosfinas con grupos ricos en electrones y voluminosos dan los mejores resultados, evitando la β-eliminación de hidrógeno de las especies organometálicas intermedias. Considerando los precedentes del Capítulo 2, se ha extendido esta metodología al acoplamiento con haloacetilenos para preparar cetonas con grupos alquino en posición γ (Capítulo 3). Curiosamente, los substituyentes del grupo alquino juegan un papel fundamental en la reactividad, pudiéndose controlar mediante la utilización de un cierto ligando. En el Capítulo 4, se ha desarrollado una nueva transformación basada en una reacción catalizada por compuestos de Ni para efectuar la síntesis de anillos de ocho eslabones mediante una reacción formal de cicloadición [4+4] de benzociclobutanonas y dienos simples. Curiosamente, dicho método muestra una especial preferencia para formar anillos de ocho eslabones sobre los, a priori, anillos de 6 eslabones que son más estables termodinámicamente. En la presente tesis doctoral se ha estudiado también la viabilidad de llevar a cabo una fijación catalítica de CO2 y la formación de enlaces C-F mediante una rotura de enlaces C-C (Capítulo 5) aunque no se han encontrado las condiciones óptimas para llevar a cabo tales transformaciones.<br>The means to promote catalytic C-C bond-functionalization has gained a considerable attention in recent years and probably can be considered one of the most challenging and vibrant subjects in organometallic chemistry. This PhD thesis deals with the design of new metal-catalyzed functionalization of C-C bonds in four-membered ring frameworks. Specifically, we have demonstrated the viability of preparing γ-arylated ketones via Pd-catalyzed cleavage of C-C bonds in tert-cyclobutanol using aryl chloride or tosylate counterparts (Chapter 2). The transformation possesses a wide substrate scope and remarkable low catalyst loadings. Selectivity was controlled by the ligand in which electron-rich and sterically-hindered phosphine ligands provided a unique reaction outcome that avoided the proclivity of alkyl metal species towards destructive β−hydride elimination. Prompted by the precedents in Chapter 2, we successfully extended the scope of the metal-catalyzed C-C bond-cleavage of tert-cyclobutanols by using halo acetylene counterparts giving γ-alkynylated ketones (Chapter 3). Interestingly, substituents on the alkyne motif showed a remarkable influence on reactivity. Of particular interest is the application profile of such methodology since γ-alkynylated ketones could promote consecutive metal-catalyzed transformations into valuable synthetic intermediates. In Chapter 4, we extended the interest for C-C bond-cleavage beyond the use of tert-cycñobutanols. Specifically, we developed a Ni-catalyzed C-C bond-cleavage event in benzocyclobutenones for preparing eight-membered rings via formal [4+4]-cycloaddition with dienes (Chapter 4). The method shows a specific preference for eight-membered rings over thermodynamically more stable six-membered rings. This PhD thesis has also studied the development of catalytic CO2 fixation and C-F bond-formation via C-C bond-cleavage (Chapter 5). While we have not found reaction conditions to effect the desired transformations, our research group is actively involved in related catalytic endeavors and it is expected that such research will shed light into the targeted CO2 fixation or C-F bond-forming reactions via C-C bond-cleavage.

The catalytic activity of ruthenium(II) bis(diimine) complexes cis-[Ru(6,6′-Cl2bpy)2(OH2)2](Z)2 (2, Z = CF3SO3; 3, Z = (3,5-(CF3)2C6H3)4B ,i.e. BArF), cis-[Ru(4,4′-Cl2bpy)2(OH2)2](Z)2 (4, Z = CF3SO3; 5, Z = BArF) and cis-[Ru(bpy)2(PR3)(OH2)](CF3SO3)2 (7, bpy = 2,2’-bipyridine, PR3 = P(C6H4F)3; 8, bpy = 2,2-bipyridine, PR3 = PPh3; 9, bpy = 4,4’-dichloro-2,2’-bipyridine, PR3 = PPh3; 10, bpy = 4,4’-dimethyl-2,2’-bipyridine, PR3 = P(C6H4F)3) for the hydrogenation and hydrogenolysis of furfural (FFR), furfuryl alcohol (FFA) and 5-hydroxymethylfurfural (HMF) was investigated. The compounds 2-5 are active and highly selective catalysts for the hydrogenation of FFR to FFA. Using 2 as catalyst at 100 °C, hydrogenation of FFR proceeded to high conversion (≥98%) and with 100% selectivity to FFA in 2 h. The catalyst cis-[Ru(6,6′-Cl2bpy)2(OH2)2](CF3SO3)2 (2) also showed some activity for hydrogenolysis of FFR and FFA at 130 °C in ethanol, giving up to 25% of 2-methylfuran (MF) yield. The catalyst 3 alsodisplayed high catalytic activity for the hydrogenation of FFA to tetrahydrofurfuryl alcohol. Catalysts 7-10 are also active towards the hydrogenation of furfural (FFR) in NMP giving >90% FFR conversion with 100% selectivity for furfuryl alcohol (FFA) in 12 h. Compounds 7-10 are active C-O bond hydrogenolysis catalysts in presence of bismuth halide Lewis acids. For example, hydrogenolysis of FFA in the presence of 1 mol% of catalyst cis-[Ru(4,4’-Cl2bpy)2(PPh3)(OH2)](CF3SO3)2 (9) and 20 mol% bismuth bromide at 180 °C/51 atm H2 pressure gave >96% conversion of FFA and 55% MF yield. Compounds 7-10 in the presence of bismuth halides, showed almost 100% conversion of HMF with a very high selectivity (65-72%) for 2,5-DMF, along with 10-12% of MF, and trace amount of 5-methylfurfural (MeFFR). In order to test the activity of ruthenium hydrides towards the C-O bond hydrogenation and hydrogenolysis of HMF, series of monocationic ruthenium complexes cis-[Ru(bpy)2(PR3)(H)](CF3SO3) (12, bpy = 2,2’-bipyridine, PR3 = P(C6H4F)3; 13, bpy = 2,2-bipyridine, PR3= PPh3; 14, bpy = 4,4’-dimethyl-2,2’-bipyridine, PR3= P(C6H4F)3) were prepared. The hydrogenation of HMF using catalysts 12-14, produced 70-72% of 2,5-DMF and 11% MF, suggesting that ruthenium hydrides are active and efficient catalysts for HMF hydrogenation.

L'étude du mécanisme de la réaction d'oxydation de l'éthanol (EOR) a été réalisée sur des électrocatalyseurs bi- et tri-métalliques à base de Pt, Rh et SnO2 sur support carboné à l'aide de méthodes électrochimiques couplées (DEMS, in situ FTIR). Deux importantes problématiques de l'EOR ont été abordées: la déshydrogénation de la molécule d'éthanol et la cassure de sa liaison C-C.L'investigation de certains paramètres expérimentaux, comme l'épaisseur de la couche d'électrocatalyseur, a permis de démontrer q'une couche active épaisse conduit à une meilleure électrooxydation plus complète de l'éthanol en CO2, mais également que l'empoisonnement de l'électrocatalyseur par de très forts adsorbats advient dans l'épaisseur de couche active.Les performances de chaque électrocatalyseur ont été comparées entre elles et ont mis en évidence une meilleure sélectivité de l'EOR sur Pt-Rh-SnO2/C, ainsi que l'engendrement de courants plus élevés à bas potentiel à température ambiante. La tendance est amplifiée à température plus élevée (T = 60 °C)<br>The study of the ethanol oxidation reaction (EOR) mechanism was performed on carbon supported bi- and tri-metallic Pt-, Rh-, SnO2-based electrocatalysts via electrochemical coupled techniques (DEMS, in situ FTIR). Two of the most important issues related to the EOR have been broached: the dehydrogenation of the ethanol molecule and its C-C bond breaking.The investigation of some experimental parameters, such as the thickness of the electrocatalyst layer, enabled demonstrating the better complete ethanol electrooxidation into CO2 for large electrocatalysts layers, combined to the enhanced poisoning effect inside the catalyst layer by very strong adsorbates.The performances of each electrocatalyst were compared and evidenced an improved selectivity of the EOR on Pt-Rh-SnO2/C, as well as the generation of higher currents at low potential at room temperature. The tendency was amplified at elevated temperatures (T = 60 °C)

Die vorliegende Dissertation beschreibt die Synthese und Charakterisierung von neuartigen perferrocenylierten, cyclischen Komplexen unter Anwendung der Cobalt-vermittelten Cyclomerisierung in Kombination mit einer C-H-Bindungsaktivierung als auch die Bildung von ferrocenylierten Phosphinoalkinid-Komplexen mit Eisen- und Cobaltcarbonylen. Die elektrochemischen Eigenschaften und die Elektronentransfer-prozesse zwischen den terminalen Ferrocenyleinheiten in den unterschiedlichen cyclischen Verbindungen wurden unter Einbeziehung der Struktur/chemischen Zusammensetzung der Brückenbausteine ermittelt. Elf perferrocenylierte, cyclische Komplexe wurden mittels [2+2] bzw. [2+2+2] Cyclomerisierung von 1,4-Diferrocenylbutadiin FcC≡C–C≡CFc (Fc = Fe(η5-C5H4)(η5-C5H5)) unter Verwendung von Dicarbonylcyclopentadienylcobalt Co(η5-C5H5)(CO)2 erhalten. Diese können in drei Gruppen unterteilt werden: (i) Produkte der Cyclodimerisierung mit zusätzlicher Kettenverlängerung, welche Cyclobutadienyl-einheiten als zentrale Brückenbausteine besitzen (3a,b und 4a,b), (ii) Produkte der Cyclodimerisierung mit gleichzeitiger CO-Insertion (6a,b,c und 7), und (iii) Produkte der Cyclotrimerisierung gefolgt von einem Ringschluss durch eine C-H-Bindungsaktivierung (5a,b,c). Die Optimierung der Reaktionsbedingungen wurde zur Ausbeutemaximierung der jeweiligen Verbindungsfamilien durchgeführt. Ein weiterer Teil dieser Forschungsarbeit bezieht sich auf die verschiedenen Reaktionsmuster von (Ferrocenylethinyl)diphenylphosphan- mit zweikernigen Eisen- bzw. Cobaltcarbonylverbindungen in Form von Dieisennonacarbonyl und Dicobaltoctacarbonyl als Reagenzien. Dabei konnten sechs gemischte Carbonyl- und Ferrocenyl-funktionalisierte Phosphinoacetylid-Komplexe mit Eisen(0) und Cobalt(0) erhalten und charakterisiert werden<br>The present PhD study focuses on the synthesis and characterization of novel perferrocenylated cyclic complexes utilizing cobalt - mediated cyclomerization in combination with C–H bond activation as well as formation of ferrocenylated phosphino-alkyne compounds with iron and cobalt carbonyls. Electrochemical properties and electron-transfer processes between terminal ferrocenyl units in the diverse cyclic compounds are explored in relation to the chemical composition of the building blocks connecting them. Eleven perferrocenylated cyclic compounds were obtained via [2 + 2] and [2 + 2 + 2] cyclomerization of 1,4-diferrocenylbutadiyne FcC≡C–C≡CFc (Fc = Fe(η5-C5H4)(η5-C5H5)) by the reaction with dicarbonylcyclopentadienylcobalt Co(η5-C5H5)(CO)2. They are subdivided into three groups: (i) products of cyclodimerization with additional chain extension, possessing cyclobutadienyl moieties as a central linkage unit (3a,b and 4a,b), (ii) products of cyclodimerization with consecutive CO insertion (6a,b,c and 7), and (iii) products of cyclotrimerization followed by cycle formation via C–H bond activation (5a,b,c). Optimization of the reaction conditions was made in order to maximize the amount of each group of compounds. Furthermore, another part of this research work focuses on diverse reaction patterns of (ferrocenylethynyl)diphenylphosphane with diironnonacarbonyl and dicobaltocta-carbonyl. Six mixed carbonyl and ferrocenyl-functionalized phospinoalkynyl compounds of iron(0) and cobalt(0) were obtained and characterized

Effective visible light photocatalysts for achieving organic reactions under mild conditions are long sought after and a rarely achieved aim in modern catalyst chemistry. Here, metal complexes and plasmonic metal NPs were assembled and used systematically for the first time as a novel photocatalyst to achieve this target. The new photocatalytic system was designed, established, and proved to be efficient in driving C-O bond cleavage of lignin model compounds and sugars dehydration to produce 5-HMF under visible light irradiation.

Aquesta tesi doctoral es basa principalment amb la síntesis de molècules petites potencialment útils per investigacions avançades. S'han utilitzat diferents metodologies per obtenir-les: 1) Cicloaddicions intramoleculars entre un alkí i una azida lliures de coure per l'obtenció de derivats de benzodiazepines. Obtenint-se una gran varietat de triazols fusionats a heterocicles de set membres. Posteriorment, s'han dut a terme proves d'activitat biològica. 2) a) Trencament d'enllaços carboni-carboni no activats d'amino alcohols i utilització d'aquest com a nucleòfil juntament amb bromurs d'aril en una reacció d'acoplament catalitzada per pal.ladi per l'obtenció de dibenzil amines. S'ha dut a terme una gran optimització dels diferents paràmetres de reacció; base, dissolvent, electròfil, temperatura, catalitzador i lligand. b) Trencament d'enllaços carboni-carboni no activats de N-alil amino alcohols i utilització d'aquest com a nucleòfil juntament amb bromurs d'aril en una reacció d'acoplament catalitzada per pal.ladi per l'obtenció d'aldehids arilats en la posició beta. S'ha dut a terme la síntesis d'un gran nombre d' amino alcohols nous i aquests han estat sotmesos a les condicions optimitzades de reacció. Demostrant que aquest transformació és útil per un gran ventall de substrats (bromurs d'aril i amino alcohols).L'enamina resultant de la reacció d'acoplament s'ha aconseguit alquilar amb vinil metil cetona amb bons rendiments però pobres diastereoselectivitats tot i així s'ha demostrant que la reacció és factible. Per finalitzar, s'ha aconseguit desenvolupar la versió enantioselectiva de l’anterior transformació obtenint bons excessos enantiomerics tot i que baixos rendiments.<br>Ésta tesis doctoral está basada principalmente en la síntesis de moléculas pequeñas potencialmente útiles para investigaciones avanzadas. Se han empleado diferentes metodologías para obtenerlas: 1) Cicloadiciones intramoleculares entre un alkino y una azida libres de cobre para la obtención de derivados de benzodiazepinas. Se han obtenido una gran variedad de triazoles fusionados a heterociclos de siete miembros. Posteriormente se han realizado pruebas de actividad biológica de las moléculas resultantes. 2) a) Escisión de enlaces carbono-carbono no activados de amino alcoholes y utilitzación de éstos como nucleófilos conjuntamente con bromuros de arilo para una reacción de acoplamiento catalizada por paladio para la obtención de derivados de dibenzil aminas. Se ha realizado una gran optimización de las condiciones de reacción; base, disolvente, electrófilo, temperatura, catalizador y ligando. b) Escisión de enlaces carbono-carbono no activados de N-alilo amino alcoholes y la utilización de éste como nucleófilo conjuntamente con bromuros de arilo en una reacción de acoplamiento catalizada por paladio para la obtención de aldehídos arilados en posición beta. Se ha realizado la síntesis de un gran numero de amino alcoholes nuevos y éstos se han sometido a las condiciones optimizadas de reacción. Demostrando que ésta transformación es útil para una gran variedad de sustratos (bromuros de arilo y amino alcoholes). La enamina resultante de la reacción de acoplamiento se ha alquilado con vinil metil cetona con buenos rendimientos pero pobres diastereoselectividades aunque se ha demostrado que la reacción es factible. Para finalizar, se ha desarrollado la versión enantioselectiva de la anterior transformación obteniendo buenos excesos enantioméricos aunque con bajos rendimientos.<br>This PhD thesis is based basically on synthesis of small molecules potentially useful for further investigations. Different strategies have been used to obtain them; 1) Copper free intramolecular cycloadditions between an azide and an akyne for the obtention of benzodiazepine derivatives. A wide range of triazoles fused to seven membered heterocycles rings have been obtained. Later, biological studies have been carried out. 2)a) Carbon-carbon bond cleavage of amino alcohols has been carried out with the subsequent use of them as a nucleophile together with aryl bromides to develop a cross-coupling reaction for the obtention of dibenzyl amines. A wide optimization of the reaction parameters was carried out; base, ligand, catalyst, electrophile, temperatura, and solent. b) Carbon-carbon bond cleavage of N- allyl amino alcohols has been carried out with the subsequent use of them as a nucleophile together with aryl bromides to develop a cross-coupling reaction for the obtention of beta arylated aldehydes. An important number of new amino alcohols have been synthesized and these have been subjected to the optimized reaction conditions. It has been demonstrated that this transformation is useful for a wide range of substrates (amino alcohols and aryl bromides). The resultant enamine has been alkylated with methyl vinyl ketone with good yields but poor diastereoselectivity. To finish the enantioselective version of beta functionalization of aldehydes has been developed obtaining good enantioselectivity but poor yields

博士<br>國立中正大學<br>化學所<br>93<br>Abstract This thesis involves the synthesis, characterization of a new class of aza-based bidentate phosphinic amide ligands, the study of catalytic applicability of the phosphinic amido palladium complexes to various Heck-type C-C formation reactions, and the kinetic and theoratic study of organotungsten Lweis acid catalyzed Diels-Alder reactions. The thesis also includes discussions of a new path for P-C cleavage which is induced by the basicity of the reaction system. The results and discussion will be categorized into four independent chapters. In the first chapter, we mainly focused our research efforts on the syntheses, structural characterization of a series of gold nanosurface-immobilized palladium(II) complex catalysts, and their catalytic reactivity towards various Heck-type C-C coupling reactions. Spherical gold nanoparticles of a diameter of 2.7 ± 0.5 nm in size were used as support for molecular palladium complex catalysts. These gold nanoparticles were obtained by the chemical reduction method using NaBH4 as the reducing agent to reduce HAuCl4・3H2O in the presence of CH3(CH2)7SH stabilizer. The compound [HS(CH2)11N(H)(O)P(2-py)2] (4), which was derived from Br(CH2)11OH, with both ends having coordination capability was specially designed as the linker between molecular metal catalysts and metal nanosurfaces. The thiol end (HS) of the anchoring linker can be put onto gold nanoparticles’ surfaces by ligand exchange at elevated temperature. Four types of “soluble” or “dispersible” gold nanoparticle-supported ligands, Au−L-A~D (Au−L = Au−S(CH2)11N(H)P(O)(2-py)2), anchored with different amounts of spacing linkers with diameters of 3-5 nm in size were synthesized by design. Again, these gold nanoparticle-supported ligands can be dispersed (or dissolved) in various organic solvents, such as CH3Cl, DMSO, MeOH, EtOH and CH3CN, etc. The direct reaction of the above-mentioned four types of ligands, Au−L-A~D, with palladium (II) complex, Pd(CH3CN)2Cl2, resulted in the formation of “soluble” gold nanosurface-immobilized palladium complexes, Au−L−Pd-A~D (Au−L−Pd = Au−S(CH2)11N(H)P(O)(2-py)2PdCl2). The diameters of the gold cores remain unchanged after palladation, and these gold nanoparticles dissolve in DMSO and MeOH fairly easily. Taking the advantage of the high solubility, A rapid and precise method to structurally characterize these systems (Au−L−Pd-A~D) using solution 1H, 13C and 31P probe NMR spectroscopy becomes accessible. In addition to the NMR technique, the atomic absorption spectroscopy (AA) was also used to determine the amount of Pd catalysts anchored on gold nanoparticle’s surface. By performing a size-and-particle calculation based on the TEM image, one can obtain the average number of Pd catalysts and stabilizers on each gold nanoparticle’s surface. These gold nanoparticle-supported palladium complexes, Au−L−Pd-A~D, were demonstrated to be highly effective catalysts for various Heck C-C coupling reactions. The turnnover frequencies (TOF) of 35000-45000 h-1 were obtained for the A-D systems. The controlled experiment of the molecular palladium complex catalyst HO(CH2)11N(H)(O)P(2-py)2PdCl2) (6) promoted Heck reactions gave TOF values of 10,000-17,000 h-1, which are 3~4 times less than those obtained for the Au−L−Pd-A~D catalytic systems. The kinetic studies revealed that a second order kinetic behavior was found for all the homogeneous 6-catalyzed Heck C-C coupling reactions. However, the kinetic studies showed that the gold nanoparticle-supported catalytic systems deviated dramatically from a normal second order kinetic behavior. In the second chapter, A new class of bidentate, aza-based phosphinic amide ligands, RNHP(O)(2-py)2, where R = CH2CH(CH2)9, HOCH2(CH2)10, (O)3Si(CH2)11, was efficiently synthesized via a one-pot Staudinger reaction of organic azides and 2-pyridylphosphines followed by in situ hydrolyses. The complex CH2CH(CH2)9NHP(O)(2-py)2 was structurally characterized, and its ORTEP drawing showed a pentavalent, trigonal pyramidal arrangement around the P center. The intermediate iminophosphoranes, CH2CH(CH2)9N=P(2-py)3, CH2CH(CH2)9N=P(Ph)- (2-py)2, CH2CH(CH2)9N=P(Ph)2(2-py) and CH2CH(CH2)9N=PPh3 were isolated by design and their hydrolyses in both acidic and basic environments were carefully studied. While all four compounds followed the expected route of a P=N cleavage to give CH2CH(CH2)9NH3+ and phosphine oxides in acidic environments. Hydrolyses of the iminopyridlphosphoranes CH2CH(CH2)9N=P(Ph)n(2-py)2-n (n = 0, 1, 2) under basic conditions produced an N-substituted phosphinic amide, CH2CH(CH2)9NHP(O)(Ph)n(2-py)2-n and a free pyridine via a P-C cleavage. The pyridylphosphorane with e-donating OMe-substituent, CH2CH(CH2)9N=PPh(2-py-4-OMe)2, hydrolyzed in a much slower rate as compared to its parent pyridylphosphoranes. On the contrary, the phenylphosphoranes with e-withdrawing halide-substituents, CH2CH(CH2)9N=P(4-X-Ph)3 (X = F, Cl), hydrolyzed in a noticeably faster rate with reference to their nonsubstituted counterpart. Three different palladium catalysts with a stable metallahexacycle formed around the Pd center were synthesized by the complexation of phosphinic amide ligand with Pd(CH3CN)2Cl2. The soluble, molecular HOCH2(CH2)10NHP(O)(2-py)2PdCl2 catalyzed Heck-type reactions of iodobenzene and acrylates and/or styrene very efficiently to give TOF values of 10,000-17,000 h-1. Both SiO2-supported homogeneous and heterogeneous, (O)3Si−(CH2)11NHP(O)(2-py)2PdCl2, are effective and regioselective catalysts for [2+2+2] alkyne cyclotrimerization reactions and can be successfully reused up to the sixth cycle without the problem of losing activity. In the third chapter, the based-catalyzed hydrolysis of two different phosphine oxides O=PX3 (X = 2-pyridy, phenyl) were carefully studied. The mixed phenyl/pyridyl phosphine oxides O=PPhn(2-py-X)3-n, where X = H, n= 1, 2； X= Me, OMe, n = 1, were hydrolyzed in the presence of base to give [HO(O)PPhn(2-py-X)2-n] and pyridine as products. The results of kinetic study showed that the rate of hydrolysis would decrease while the number of phenyl group increases as follows: O=P(2-py)3> O=PPh(2-py)2> O=PPh2(2-py). However, the measured reaction barriers for hydrolyses were found to be increased when the H atom at the para-position on the pyridyl group of O=PPh(2-py)2 replaced with the e-donating groups, OMe or Me. The rates of hydrolyses were in the following order: O=PPh(2-py)2> O=PPh(2-py-4-Me)2 > O=PPh(2-py-4-OMe)2. For phenyphosphine oxides O=P(4-Ph-X)3, where X = F and Cl, the hydrolyses can be carried out to give [HO(O)P(Ph-X)2-n] and halogenated benzene as products. The hydrolysis rates for this series of phenylphosphine oxides were found in the following order: O=P(Ph-F)3> O=P(Ph-Cl)3> O=PPh3. The parent triphenylphosphine oxide, however, would not undergo hydrolysis even at temperature of 190 oC for days. The energy barriers of the based-catalyzed hydrolysis were calculated by using HF/6-31+G* and B3LYP/6-31+G* level of theory, and the results were consistent with the experimental observation. We found that the energy barriers for the hydrolyses followed the similar trend shown below in its decreasing order: O=P(2-py)3> O=PPh(2-py)2> O=PPh(2-py-4-Me)2 > O=PPh(2-py-4-OMe)2 > O=PPh2(2-py)> O=P(Ph-F)3> O=P(Ph-Cl)3> O=PPh3. In the last chapter, the catalytic reactivity of tungsten Lewis acid [P(2-py)3W(CO)(NO)2]2+ toward Diels-Alder reaction of cyclopentadiene and methyl vinyl kentone and/or 1,3-cyclohexadiene and methyl vinyl kentone were discussed. Comprehensive kinetic measurements of both the uncatalyzed and the corresponding 1-catalyzed Diels-Alder reaction of cyclopentadiene and methyl vinyl kentone as well as cyclohexadiene and methyl vinyl kentone were conducted at various temperatures. Based on the results of these kinetic works, we were able to obtain lavish information to quantify the catalyst efficiencies. For example, the activation energies, preexponetial factors, entropies of the transition state, the reaction rate constants, and reaction order were determined. According to these results, a reasonable mechanism and the reaction rate determining step of the 1-catalyzed Diels-Alder reactions of cyclopentadiene and methyl vinyl kentone as well as cyclohexadiene and methyl vinyl kentone were therefore suggested. The experiment of this chapter is research of continuing the laboratory schoolmate, so does not do the detailed discussion in this thesis, only publish it the thesis and examine and enclose it in the appendix.

博士<br>國立中央大學<br>化學研究所<br>96<br>This thesis is aimed to study the relationship between the photoinduced intramolecular electron transfer processes and the excited-state C-N bond cleavage reaction as well as intramolecular exciplex formation of a series of amine-bridge-stilbene derivatives. The fluorescence spectra of DPhI, MPhI and DEtI show dual fluorescence in polar solvents, but DCEtI and DPyI display only the locally-excited (LE) fluorescence in both nonpolar and polar solvents. Compounds DPhI and MPhI in nonpolar and polar solvents and DPyI and DPyCI in CH3CN undergo the C-N bond cleavage, leading to the formation of HI and CI of higher fluorescence quantum yields (Φf). However, such a C-N bond fragmentation reaction was not observed for DEtI in either nonpolar or polar solvents. The Φf and the quantum yields of the C-N bond cleavage reaction (Φfra) for DPyI and DPyCI increase as increasing the solvent polarity. In contrast, an opposite solvent dependence of Φfra was observed for DPhI and MPhI because the intramolecular electron transfer and back electron transfer processes locate in the Marcus normal and inverted region, respectively, and the value of ΦBET increases more than that of ΦICT with increasing the solvent polarity. Compounds DPyI2 and DPyI3 display only the LE fluorescence in both nonpolar and polar solvents, but the fluorescence quantum yields decrease and the fluorescence life times increase with increasing the solvent polarity. This indicates the presence of electron donor and acceptor interactions. Compounds DPhI2 and DPhI3 show dual fluorescence in moderate and highly polar solvents, and the long-wavelength emission band results from intramolecular exciplexes. When compared with the one-mothylene-bridged compounds, compounds DPyI2, DPyI3, DPhI2 and DPhI3 do not undergo the cleavage of C-N bond in both nonpolar and polar solvents.

The selective transformation of carbon-carbon and carbon-hydrogen bonds represents an attractive approach and rapidly developing frontier in synthesis. Benefits include step and atom economy, as well as the ubiquitous presence in organic molecules. Advances to this exciting realm of synthesis are described in this thesis with an emphasis on the development of catalytic, selective reactions under mild conditions. Additionally some applications of the methodologies are demonstrated. In Chapter 1, the first examples of inter-and intramolecular enantioselective conjugate alkenylations employing organostannanes are reported. A chiral, cationic Rh(I)-diene complex catalyzed the enantioselective conjugate addition of alkenylstannanes to benzylidene Meldrum’s acids in moderate enantiomeric ratios and yields. Notably, the cationic and anhydrous conditions required for the asymmetric alkenylation are complementary to existing protocols employing other alkenylmetals. In Chapter 2, a domino, one-pot formation of tetracyclic ketones from benzylidene Meldrum’s acids using Sc(OTf)3 via a [1,5]-hydride shift/cyclization/Friedel-Crafts acylation sequence is described. Respectable yields were obtained in accord with the ability to convert to the spiro-intermediate, and considering the formation of three new bonds: one C-H and two C-C bonds. An intriguing carbon-carbon bond cleavage was also serendipitously discovered as part of a competing reaction pathway. In Chapter 3, the pursuit of novel C-H bond transformations led to the development of non-carbonyl-stabilized rhodium carbenoid Csp3-H insertions. This methodology enabled the rapid synthesis of N-fused indolines and related complex heterocycles from N-aziridinylimines. By using a rhodium carboxamidate catalyst, competing processes were minimized and C-H insertions were found to proceed in moderate to high yields. Also disclosed is an expedient total synthesis of (±)-cryptaustoline, a dibenzopyrrocoline alkaloid, which highlights the methodology. In Chapter 4, the Lewis acid promoted substitution of Meldrum’s acid discovered during the course of the domino reaction was explored in detail. The protocol transforms unstrained quaternary and tertiary benzylic Csp3-Csp3 bonds into Csp3-X bonds (X = C, N, H) and has even shown to be advantageous with regards to synthetic utility over the use of alternative leaving groups for substitutions at quaternary benzylic centers. This reaction has a broad scope both in terms of suitable substrates and nucleophiles with good to excellent yields obtained (typically >90%).

碩士<br>國立中正大學<br>化學暨生物化學研究所<br>106<br>As the second largest renewable energy source in the world, how lignin can be effectively transformed into higher economic crops is the goal pursued by modern scientists. Among them, the functionalization of carbon and oxygen bonds to convert lignin to other compounds is a common method at present. However, the problem is that compared to common carbon and halogen bonds, the higher bond energy of carbon and oxygen bonds leads to less dissociation, so the use of organometallic catalysis can lower the activation energy of the reaction and thus facilitate the reaction, resulting in a more rapid rate of conversion. A common method is to use a nickel metal complex, which is catalyzed by a strong electron-donor ligand, so that the C–O bond is more easily oxidized and the functionalization reaction is completed. We utilized nickel and Grignard reagent to performed catalytic C–O bond cleavage. The inert C–O bond could be cleaved by a new type of nickel-catalyzed cross-coupling reaction with the assistance of Grignard reagents with an electron-rich carbodicarbene ligand synthesized by our laboratory. The scope of substrates, application and proposed mechanism of this reaction will be reported in this work.

<p>Terphenyl diphosphines bearing pendant ethers were prepared to provide mechanistic insight into the mechanism of activation of aryl C–O bonds with Group 9 and Group 10 transition metals. Chapters 2 and 3 of this dissertation describe the reactivity of compounds supported by the model phosphine and extension of this chemistry to heterogenous C–O bond activation.</p> <p>Chapter 2 describes the synthesis and reactivity of aryl-methyl and aryl-aryl model systems. The metallation of these compounds with Ni, Pd, Pt, Co, Rh, and Ir is described. Intramolecular bond activation pathways are described. In the case of the aryl-methyl ether, aryl C–O bond activation was observed only for Ni, Rh, and Ir.</p> <p>Chapter 3 outlines the reactivity of heterogenous Rh and Ir catalysts for aryl ether C–O bond cleavage. Using Rh/C and an organometallic Ir precursor, aryl ethers were treated with H2 and heat to afford products of hydrogenolysis and hydrogenation. Conditions were modified to optimize the yield of hydrogenolysis product. Hydrogenation could not be fully suppressed in these systems.</p> <p>Appendix A describes initial investigations of bisphenoxyiminoquinoline dichromium compounds for selective C2H4 oligomerization to afford α-olefins. The synthesis of monometallic and bimetallic Cr complexes is described. These compounds are compared to literature examples and found to be less active and non-selective for production of α-olefins.</p> <p>Appendix B describes the coordination chemistry of terphenyl diphosphines, terphenyl bisphosphinophenols, and biphenyl phosphinophenols proligands with molybdenum, cobalt, and nickel. Since their synthesis, terphenyl diphosphine molybdenum compounds have been reported to be good catalysts for the dehydrogenation of ammonia borane. Biphenyl phosphinophenols are demonstrated provide both phosphine and arene donors to transition metals while maintaining a sterically accessible coordination sphere. Such ligands may be promising in the context of the activation of other small molecules.</p> <p>Appendix C contains relevant NMR spectra for the compounds presented in the preceding sections.</p>

碩士<br>國立成功大學<br>化學系碩博士班<br>95<br>1,2,3,4-Tetraphenylnaphthalene (33a) can be prepared from the reaction of triphenylphosphine and diphenylacetylene (31a) in the presence of the palladium catalyst. The catalytic efficiencies of several palladium complexes, the reactivity of phenylphosphine compounds and the contributions from solvents and additives have been examined. The reaction conditions have been optimized: When the solution of triphenylphosphine and 31a in acetonitrile was added to our developed catalytic system by a syringe pump at 110 ℃, and 33a could be obtained in 62% yield. To our best knowledge, this is the first example for the preparation of naphthalenes via the activation of a phenyl C-P bonds and C-H bonds. Based on this synthetic method, five naphthalene derivatives have been prepared in 22-62% yields. 5,8-Dimethyl-1,2,3,4-tetraphenylnaphthalene (35a) can be accessible directly from p-xylene and 31a under the catalysis of palladium acetate. This protocol provides three obvious advantages: simple, clean and atomic economics. From the structure of 35, an arene offers a〝benzo〞unit to construct a naphthalene core via double aryl C-H activations. Our coworker has optimized the reaction conditions. Based on the procedure, four highly substituted naphthalenes 35ab, 35ac, 35bb and 35cc have been prepared in 22-45% yields.

碩士<br>國立成功大學<br>化學系<br>103<br>In our effort to understanding high-valent vanadium sulfur chemistry, two tris(thiolato)phosphine ligands, [PS3”]H3 and [PS3*]H3 has been untilized to interact with high-valent vanadium species.([PS3”]H3=[P(C6H3-3-Me3Si-2-S)3]3-. [PS3*]H3=[P(C6H3-3-Ph-2-S)3]3-). At this work, several five vanadium-thiolate complexes have been obtained and characterized. They are [V(PS3”)2][NEt4] (1a), [V(PS3*)2][NPr4] (1b),[VIV(PS2”SH)(PS3”)][PPh4] (2a), [VIV(PS3*)(PS2*SH)][NPent4] (2b), and [VIV(PS3*)2] [(NPr4)2] (3). The reactivity of them with air has been explored. The evidences were supported by Ultraviolet-visible spectroscopies and ESI-MS studies. The hepta-coordinated [VIV(PS2”SH)(PS3”)]- (2a), and [VIV(PS3*)(PS2*SH)]- (2b) proceed air oxidation to form the octa-coordinated [V(PS3”)2]- (1a) and [V(PS3*)2]- (1b), respectively. The octa-coordinated [VIV(PS3*)2]2- (3) can be oxidized via one electron oxidation to form complex 1b by air oxidation or [Fe(C5H5)2][BF4] oxidation. From ESI-MS studies, complex 1a and 1b, species with resonance forms between V(V)-thiolate and V(IV)-thiyl radical, can reacted with H2O and form 2a and 2b by homolytic cleavage of the O-H bond. In addition, complex 1a and 1b also reacted with methanol via homolytic cleavage of O-H bond and C-O bond. Consequently, it led to the formation of 2a, [VIV(PS3”)(PS2SCH3”)]- (4a), and 2b, [VIV(PS3*)(PS2SCH3*)]- (4b), respectively. The kinetic studies of 1a with a series of substrates, such as H2O, toluene, CH3CN, fluorene and THF, have been investigated. From the kinetic isotope effect (KIE), O-H bond cleavage in H2O is an important component of the rate-determining step. It is interesting that 1a prefers to cleave stronger O-H bonds rather than C-H bonds. This finding was proposed that the preorganization step via the assistant of the hydrogen bonding interaction between substrates and 1a plays a key role which reduces the activation energy barrier.