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Dissertations / Theses on the topic 'Ketenes'

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Published: 4 June 2021

Last updated: 31 July 2024

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1

Giang, Yun-Seng F. (Yun-Seng Frank). "Intramolecular 2+2 Cycloadditions of Ketenes." Thesis, North Texas State University, 1986. https://digital.library.unt.edu/ark:/67531/metadc331159/.

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The objective of this study was to explore intramolecular ketene cycloadditions with the anticipated results of developing new synthetic methodology for the synthesis of polycyclic compounds difficult to obtain by other procedures. (o-Alkenylphenoxy)ketenes were initially selected for this study because these ketenes provided a favorable proximity for the intramolecular [2+2] cycloaddition reactions. The difunctional precursors, (o-alkenylphenoxy)- acetic acids, were readily prepared from o-alkenylphenols and ∝-halocarboxylic acids and were converted to the corresponding acid chlorides by reaction with oxalyl chloride. The acid chlorides were dehydrochlorinated to the corresponding (o-alkenylphenoxy)ketenes by treatment with triethylamine. The ketenes undergo a facile intramolecular [2+2] cycloaddition to give polycyclic eye 1obutanones. The (o-vinylphenoxy)ketenes are clearly more reactive than the (o-allylphenoxy)ketenes and provide much better yields of the cycloaddition products because of electronic effects in the transition state in the cycloaddition process. The intramolecular [2+2] cycloadditions of keteniminium salts were included in this study as a more electrophilic alternative to ketenes that will react with less nucleophilic carbon-carbon double bonds. However, the use of keteniminium salts instead of ketenes in Intramolecular cycloadditions does have some limitations. The synthesis of benzofurans via the intramolecular [2+2] cycloadditions of (o-acylphenoxy)ketenes was accomplished. The initially formed ß-lactone cycloaddition products spontaneously underwent decarboxylation to the benzofurans. The aromaticity of the benzofurans is apparently a very strong driving force for the cycloaddition. During the course of this study, two new synthetic methods were discovered which in many instances represent a significant Improvement over existing methods. The Wittig Reactions of ketoacids without protecting the carboxyl groups provide a reliable source of the precursor unsaturated acids needed for intramolecular ketene-olefin cycloadditions. Also, the one-pot preparation of intramolecular ketene cycloaddition products from the carboxylic acid via the tosylate represents a new synthetic method. This procedure eliminates the acid halide preparation, isolation and purification step, thereby significantly simplifying the synthesis.

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2

Palmer, Prem. "Structure, Energetics and Reactions of Bisketenes: An Ab Initio and Density Functional Theory Study." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc501272/.

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The effect of varying substituents on structure and energies of bisketenes was studied using ab initio methods. Effect of substituents on ring closing reaction of bisketenes to the corresponding cyclobutenediones was also studied using ab initio methods. One or two of the following substituents were used to study the effect of varying substituents: BH2, CH3, NH2, OH, F, AlH2, SiH3, PH2, SH, Cl. Studies were done at the Hartree-Fock (HF), Møller-Plesset (MP2), and Density Functional Theory (B3LYP) levels of theory using the 6-31G* basis set.

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3

Jiang, Bo. "Homo- and co-polymerization of disubstituted ketenes." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR02/document.

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Ce travail vise à synthétiser avec un rendement satisfaisant de nouvelles architectures de polymères à hautes performances, possédant une structure définie et une bonne fenêtre de transformation, sur la base de cétènes aliphatiques ou aromatiques disubstitués. Les synthèses de diméthylcétène (DMK), méthyléthylcétène (MEK), diéthylcétène (DEK), éthylphénylcétène (EPK) et diphénylcétène (DPK) ont été étudiées. Puis l’homo- et la copolymérisation de ces monomères avec différents amorceurs ont été étudiées. L’influence de l’encombrement stérique présent sur les cétènes influence grandement leur réactivité. Ainsi, des mélanges DMK / DEK et DMK / DPK ont été copolymérisés avec succès pour donner des polycétones dont les propriétés thermiques présentent une plage de transformation satisfaisante (Tf ~ 160°C et Td₅% ~ 260°C). Le DMK est le seul monomère conduisant à un homopolymère par voie cationique classique. Les tentatives de photopolymérisation cationique n’ont pas conduit à la polycétone attendue. L’utilisation de métallocènes conduit à la structure polyester. Des structures semi cristallines de très haute masse molaire et faible polydispersité ont été ainsi obtenues (Mn ~ 300000 g·mol−1, Ɖ < 2, Tg ~ 70°C, Tf ~ 200°C,Td₅% ~ 330°C)
This study is aimed at synthesizing with a satisfying yield new architectures of high performance polymers, possessing a neat structure and good processing window, on the basis of disubstituted aliphatic or aromatic ketenes. The synthesis of dimethylketene (DMK), methylethylketene (MEK), diethylketene (DEK), ethylphenylketene (EPK) and diphenylketene (DPK) were approached. Then homo and copolymerization of these monomers with different initiators were studied. The influence in steric hindrance of the monomers affected their reactivity. Thus copolymers based on DMK/ DEK and DMK / DPK were successfully obtained and afforded polyketones having good thermal properties and processing window (Tm ~ 160°C and Td₅% ~ 260°C). Only DMK homopolymerized by classic cationic initiation. Photopolymerization did not lead to any polymer formation. Initiation with metallocenes polymerized DMK to a crystallized polyester in an insertion chain growth mechanism. Excellent properties (Mn ~300 000 g·mol−1, Tg ~ 70°C, Tm ~ 200°C, Td₅% ~ 330°C) were obtained

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4

Rafai, Far Adel. "Polymer-bound ketenes and allenes, preparation and applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0026/NQ49839.pdf.

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5

Gu, Yi Qi. "Intramolecular [2+2] Cycloadditions of Phenoxyketenes and Intermolecular [2+2] Cycloadditions of Aminoketenes." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc332334/.

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One objective of this study was to explore the intramolecular [2+2] cycloadditions of phenoxyketenes to carbonyl groups with isoflavones and benzofurans as target compounds. The other objective was to investigate the eyeloaddition reactions of rarely studied aminoketenes. The conversion of 2-(carboxyalkoxy)benzils to the corresponding phenoxyketenes leads to an intramolecular [2+2] cycloaddition to ultimately yield isoflavones and/or 3-aroylbenzofurans. The product distributions are dependent upon the substitution pattern in the original benzil acids. The initial cycloaddition products, β-lactones, are isolated in some instances while some β-lactones spontaneously underwent decarboxylation and could not be isolated. The ketene intermediate was demonstrated in the intramolecular reaction of benzil acids or ketoacids with sodium acetate and acetic anhydride. It is suggested that sodium acetate and acetic anhydride could serve as a source for the generation of ketenes directly from certain organic acids. The treatment of ketoacids with acetic anhydride and sodium acetate provides a simpler procedure to prepare benzofurans than going through the acid chloride with subsequent triethylamine dehydrochlorination to give the ketenes. N-Ary1-N-alkylaminoketenes were prepared for the first time from the corresponding glycine derivatives by using p-toluenesulfonyl chloride and triethylamine. These aminoketenes underwent in situ cycloadditions with cyclopentadiene, cycloheptene and cyclooctenes to yield only the endo -bicyclobutanones. The cycloheptene and cyclooctene cycloaddition products underwent dehydrogenation under the reaction conditions to yield bicycloenamines. A mechanism is proposed for this dehydrogenation involving a radical cation of the arylalkylamine. (N-Phenyl-N-methyl) aminomethylketene was also prepared and found to undergo an intramolecular Friedel-Crafts type acylation to yield an indole derivative when prepared by the acetic anhydride, sodium acetate method. The in situ cycloaddition of N-aryl-N-alkyl aminoketenes with various imines was found to form predominately cis-3-amino-2-azetidinones. A mechanism involving a dipolar intermediate is provided whereby the structure of the intermediate is determined by both electronic and steric effects. The stereochemistry of the resulting β-lactams is dependent upon the structure of the dipolar intermediate.

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6

Tickner, Christopher Alan. "Alkaloid catalysed addition to ketenes : a method for asymmetric synthesis." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416878.

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7

Winders, J. A. "Synthesis of natural products via intramolecular trapping of photogenerated ketenes." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381729.

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8

Xiang, Yuanhui. "SILYL KETENES AS BUILDING BLOCKS FOR SMALL MOLECULES AND POLYMERS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1561113802285453.

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9

Taggi, Andrew Edmund. "The development of novel methodology for catalytic asymmetric synthesis ketenes." Available to US Hopkins community, 2003. http://wwwlib.umi.com/dissertations/dlnow/3080776.

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10

Kumar, Ganesh Angusamy. "Substituent Effects: A Computational Study on Stabilities of Cumulenes and Low Barrier Hydrogen Bonds." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2566/.

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The effect of substituents on the stabilities of cumulenes-ketenes, allenes, diazomethanes and isocyanates and related systems-alkynes, nitriles and nitrile oxides is studied using the density functional theory (B3LYP, SVWN and BP86) and ab initio (HF, MP2) calculations at the 6-31G* basis set level. Using isodesmic reactions, correlation between stabilization energies of cumulenes and substituent group electronegativities (c BE) is established and the results from DFT and MP2 methods are compared with the earlier HF calculations. Calculations revealed that the density functional methods can be used to study the effect of substituents on the stabilities of cumulenes. It is observed that the cumulenes are stabilized by electropositive substituent groups from s -electron donation and p -electron withdrawal and are destabilized by electronegative substituent groups from n-p donation. The calculated geometries of the cumulenes are compared with the available experimental data.High level ab initio and density functional theory calculations have been used to study the energetics of low-barrier hydrogen bond (LBHB) systems. Using substituted formic acid-formate anion complexes as model LBHB systems, hydrogen bond strength is correlated to the pKa mismatch between the hydrogen bond donor and the hydrogen bond acceptor. LBHB model systems are characterized by the 1H-NMR chemical shift calculations. A linear correlation between the calculated hydrogen bond strength and the predicted 1H-NMR chemical shift was established. It is concluded that the pKa matching within the enzyme active site of the two species involved in the LBHB is important to maximizing catalytic stabilization.

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11

Dad, Mohammad M. (Mohammad Mehdj). "Aminoketene. Cycloaddition of Ketenes and Imines to Yield β- or δ- Lactams." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332534/.

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The purpose of this investigation was to provide a systematic study of the cycloaddition pf (N-alkyl-N-phenylamino)- methoxy-and dichloroketenes to various imines and to investigate the stereochemistry of these cycloadditions.

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12

Shi, Chongsheng. "Synthesis of benzocarbazoles, indoloquinolines and indolonaphthridines from thermolysis of benzoenynyl ketenimines and carbodiimides." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2119.

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Thesis (Ph. D.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains ix, 82 p. : ill. Includes abstract. Includes bibliographical references (p. 70-80).

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13

Middleditch, Michael. "Towards a catalytic carbonyl olefination reaction using metal oxo complexes and ketenes." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430565.

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14

Aguirre, Kohnen Amanda L. (Amanda Lucille). "Synthesis of 3-aminocyclobutenones via [2 + 2] cycloaddition of ynamides and ketenes." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/73390.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Ynamides react with various classes of ketenes in intermolecular [2 + 2] cycloaddition to afford substituted cyclobutenones with complete regioselectivity. The cycloaddition substrates are easily assembled from amine derivatives by copper-catalyzed N-alkynylation with acetylenic bromides. The alkynylation reaction provides access to thermally sensitive compounds such as diynamides. Synthesis of the requisite halo diynes is achieved by Sonogashira coupling followed by base-mediated elimination at low temperature.
by Amanda L. Aguirre Kohnen.
S.M.

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15

Ko, Jinren. "Synthetic Applications of Ketene Cycloadditions: Natural and Novel Pyrethroid Insecticides." Thesis, North Texas State University, 1985. https://digital.library.unt.edu/ark:/67531/metadc331031/.

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A new synthetic route to natural and novel pyrethroid acids was developed utilizing ketene cycloaddition which is a significant improvement over existing syntheses. The newly synthesized pyrethroid acids were converted to pyrethroid esters and used to study structure-activity relationships. The cycloaddition of dichloroketene with 2,5-dimethyl-2,4-hexadiene yields (2+2) cycloaddition products, 2,2-dichlorocyclobutanones. The reductive removal of one chlorine atom from these cycloaddition products gave monochlorocyclobutanones which underwent a Favorskii-type ring contraction to yield cis- and trans-chrysanthemic acids. 4-Methyl-1,3-pentadiene was also used as a precursor in this synthetic scheme to yield an analogue of the chrysanthemic acid. These results are consistent with a concerted cycloaddition process involving a dipolar transition state. The zinc reduction is not a regiospecific reaction which accounts for the two regioisomers of the monochlorocyclobutanones. The Favorskii-type ring contraction is a regiospecific reaction. A variety of different bicyclo(3.1.0)alkenecarboxylates and bicyclo(4.1.0)heptenecarboxylates were synthesized from alkylcyclopentadiene and fulvene derivatives. These new bicyclo pyrethroid acids are structurally similar to the natural chrysanthemic acid but are rigid and locked in a single conformation which is likely the least stable conformer of the natural acid. The acids were converted to pyrethroid esters and tested against the housefly and cockroach. The test results indicate that the bicyclo pyrethroids synthesized are not as active as the natural pyrethroid. Apparently, these bicyclo pyrethroids with structures similar to the less stable conformer of the natural pyrethroids are of little consequence as it binds to the target site in the insect. In an effort to learn more about the conformational requirements of the pyrethroid acid, a new bicyclo-spiro pyrethroid system with a structure similar to the most stable conformation of the natural pyrethroid was designed and synthesized. These bicyclo-spiro pyrethroids were derived from a new isopropylidenecyclobutane derivatives as a starting compound instead of a conjugated diene. The test results of these bicyclo-spiro pyrethroid esters revealed a much greater activity against the housefly and cockroach. This study establishes that the more stable conformer of the natural pyrethroid acid provides a much higher toxicity against the insects tested.

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16

Davie, Christopher P. "[4 + 1] annulation reactions of (trialkylsilyl)ketenes : synthesis of substituted indanones and cyclopentenones." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33648.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2005.
Vita.
Includes bibliographical references.
(Trialkylsilyl)vinylketenes ("(TAS)vinylketenes") and (trialkylsilyl)arylketenes ("(TAS)- arylketenes") function as versatile four-carbon building blocks for the synthesis of carbocyclic and heterocyclic compounds. A new [4 + 1] annulation strategy for the synthesis of substituted 2-indanones, based on the reaction of TAS-arylketenes with trimethylsilyl diazomethane, has been developed. In addition, a new class of carbenoid reagents for our previously reported [4 + 1] cyclopentenone annulation has been identified. Studies have shown that the reaction of a- benzotriazolyl organolithium compounds (prepared via metallation of readily available N- substituted benzotriazole derivatives) with (TAS)vinylketenes generates dienolate intermediates which cyclize to form cyclopentenones. Most cases of the annulation proceed with a high level of diastereoselectivity, and deliver highly substituted and functionalized 2-silylcyclopentenones in good yield. Furthermore, the vinylsilane moiety incorporated in the [4 + 1] annulation products provides a useful handle for further synthetic transformations. Preliminary studies focused on elaboration of the cyclopentenone products have laid the groundwork for future applications of this [4 + 1] annulation methodology.
by Christopher P. Davie.
Ph.D.

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17

Friend, Christopher Lyndon. "New approaches to catalytic enolate chemistry." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285676.

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18

Rahman, S. S. "Generation of ketenes by photolysis of cyclobutanones : A versatile route to natural product synthesis." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384092.

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19

Nakai, Takashi S. M. Massachusetts Institute of Technology. "Asymmetric synthesis of amines by the catalytic enantioselective additions of hydrazoic acid to ketenes." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41770.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.
Includes bibliographical references.
The development of a planar-chiral catalyst for the enantioselective additions of HN3 to hindered ketenes was investigated. It was demonstrated that a new planar-chiral catalyst (1.5) is an excellent catalyst for the enantioselective addition of HN3 to hindered ketenes, en route to enantioenriched amines. The addition of HN3 to a ketene is likely occurring by the Bronsted acid catalysis mechanism. The evidence in support of the Bronsted acid catalysis mechanism include stereochemical and spectroscopic results, which are consistent with data from other additions believed to occur by the Bransted acid catalysis mechanism. Enantioenriched amines generated are a family of compounds distinct from the products yielded by earlier Bronsted acid catalyzed processes. In addition, with the use of highly acidic HN3, the pH range in which a planar-chiral catalyst can function as a Bransted acid catalyst was demonstrated to be much larger than previously known. ... The development of a tertiary amine catalyst for the enantioselective additions of HN3 to unhindered ketenes was investigated. Preliminary results indicate that catalyst 2.3a exhibits promising enantioselectivity for the addition of HN3 to unhindered ketenes and appears to be complementary to planar-chiral catalyst 1.5 in terms of substrate scope. ...
by Takashi Nakai.
S.M.

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20

Firooznia, Fariborz. "Application of ketenes and allenes in the total synthesis of diterpene quinones and indoles." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32648.

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21

Douglas, James J. "NHCs in organocatalysis : azolium enolate generation and synthetic applications." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3085.

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This thesis details investigations into organocatalytic reactions promoted by N Heterocyclic Carbenes (NHCs) that proceed via an assumed azolium enolate intermediate. Initial research focused on the catalytic asymmetric synthesis of β-lactones via an NHC-catalysed formal [2+2] cycloaddition of alkylarylketenes and chloral. This process operated in good yield (typically >70%) and moderate diastereoselectivity (typically ~75:25 dr, anti:syn) for a range of alkylarylketenes. The enantioselectivity was consistently high for the major anti diastereomer (typically >80% ee) and minor syn diastereomer (typically >70% ee). Interestingly, when a ketene bearing a 2 substituent on the aryl ring, or one that included an α-branched alkyl group was used, an exclusive asymmetric chlorination pathway was accessed. This is, to the best of our knowledge, the first use of chloral as an electrophilic chlorination agent. This methodology was found to be applicable to a range of 2-arylsubstituted alkylarylketenes in good yield and enantioselectivity (typically >70% yield and up to 92% ee). The scope of this reaction with respect to the aldehyde moiety was then analysed with 2-nitrobenzaldehyde providing β-lactone products in excellent dr (up to 94:6 syn:anti) and with good yield and enantioselectivity (typically >60% yield and >80% ee). Importantly these β-lactone products were amenable to further derivatisation with transformation to β-amino- and β-hydroxy acids. Following the identification of an NHC-catalysed chlorination reaction using chloral, the development of a general procedure was undertaken. Following a wide screen of electrophilic chlorination sources, 2,3,4,5,6,6 hexachlorocyclohexa 2,4 dienone was identified as optimal, operating in excellent yield (up to 97%) but in moderate to poor levels of enantioselectivity (21−61% ee). Efforts to expand the practicality of azolium enolate processes focused on the use of α-aroyloxyaldehydes as bench stable mono-substituted ketene surrogates. A range of differentially substituted α-aroyloxyaldehydes allowed access to δ-lactones via the NHC-catalysed [4+2] cycloaddition between azolium enolates and β,γ unsaturated α ketoesters. Following initial optimisation the reaction proceeded in exquisite diastereo- and enantiocontrol (typically >95:5 dr and >99% ee).

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22

Fenwick, Michael H. "A new method for generating the cyclopropylmethyl radical, and generation of ketenes with Proton Sponge." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62937.pdf.

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23

Liu, Ronghua. "Stable monoketenes, bisketenes, polymer bound ketenes andaryl substituent effects on the ring closure of 1,2-bisketenes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0004/NQ27683.pdf.

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24

Friel, Donna Kay. "Catalytic enantioselective synthesis of tertiary propargylic alcohols : Al-catalyzed asymmetric alkylation of pyridyl-ynones with dialkylzinc reagents." Thesis, Boston College, 2008. http://hdl.handle.net/2345/25.

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Thesis advisor: Amir H. Hoveyda
General and efficient methods for catalytic enantioselective synthesis of tertiary alcohols prepared by the addition of C-Metal nucleophiles to ketones
Thesis (MS) — Boston College, 2008
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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25

Wu, An-hsiang. "Syntheses of Highly Strained Energetic Molecules and Development of New Synthetic Methodology." Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc331132/.

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The objective of this study was to synthesize new energetic, strained, saturated polycyclic compounds. For this purpose, new methodology has been developed, as follows: (i) Ketenes have been generated in situ via treatment of aldo-, keto- or alkenoic acid with either toluenesulfonyl chloride or 2-chloro-1-methylpyridfniurn iodide (Mulkaiyama's reagent). The reactive intermediates thereby generated have been found to undergo intramolecular [2+2] cycloaddition reactions in these systems.

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26

Lawlor, Michael David. "New methodology for the generation and cycloadditions of thio-substituted ketenes ; A synthetic approach to the taxol A-ring." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10431.

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27

Ye, Guozhong. "Synthesis and reactions of cyclic ketene-N,N-acetals." Diss., Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-09142008-210135.

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28

Bradbury, James Edward. "AKD sizing reversion : the vapor phase adsorption of the thermal decomposition products of alkyl ketene dimmer onto cellulose substrates." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/7013.

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29

Ramiandrasoa, Guy. "Etude de l'accès sélectif aux esters 2,3-difonctionnels." Rouen, 1993. http://www.theses.fr/1993ROUES017.

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Plusieurs voies d'accès aux esters 2,3-difonctionnels ont été évaluées dans les séries dihydroxy- et aminohydroxyesters en raison de l'importance des produits naturels correspondants ou de leurs homologues synthétiques. Les précurseurs de ces synthèses sont les α et β cétoesters fonctionnels et leurs formes protégées ainsi que les dérivés silylés des dialkoxyacétates d'alkyle, acétals de cétène silylés fonctionnels qui représentent les équivalents synthétiques des synthons C2 oxoester « CO-COOR ». L'étude structurale des composés préparés est axée sur la RMN 1H et 13C ainsi que sur les caractéristiques des spectres de masse et fait l'objet d'un développement particulier

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30

Sinnes, Jean-Luc. "Synthèse de la partie sud du soraphen A." Nancy 1, 1993. http://www.theses.fr/1993NAN10251.

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Le but de cette thèse est la synthèse d'analogues de la partie sud du soraphen A, un puissant fongicide naturel. Dans un premier temps, des composés faiblement substitués comme les 2-carboxymethyl-2,4-dihydroxy-tetrahydropyrannes ont été préparés sous forme racémique selon une nouvelle approche impliquant une réaction de condensation trimoléculaire entre le dicetene, un aldéhyde et un alcool. Des préparations enantiosélectives de ces composés ont ensuite été réalisées par condensation d'enolates d'esters sur les (4r)- et (4s)-hydroxy-tetrahydropyran-2-one enantiomeriquement purs, préparés selon trois voies différentes; une voie enzymatique et deux voies chimiques. Divers composés portant toutes les fonctionnalités du cycle tetrahydropyrannique du soraphen A ont également été préparés, d'une part, par dégradation contrôlée de la molécule naturelle et d'autre part, par synthèse nécessitant une suite de condensations aldoliques stéréosélectives

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31

Hayki, Najib. "Synthèse et caractérisation de nouveaux polymères obtenus à partir de l'éthylcétène." Phd thesis, INSA de Rouen, 2011. http://tel.archives-ouvertes.fr/tel-00633323.

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L'objectif de cette étude est de synthétiser de nouveaux polymères aux propriétés spécifiques, en utilisant pour la première fois comme monomère un aldocétène : l'éthylcétène. La synthèse de l'éthylcétène a été entreprise en utilisant deux procédés distincts :d'une part la méthode de McCarney, qui a permis de le préparer dans un solvant par entraînement à la vapeur, et d'autre part le craquage de l'anhydride butyrique à 575°C sous 40mbar.La polymérisation ionique de l'éthylcétène a ensuite été réalisée, dans différentes conditions de solvant, de température et avec plusieurs amorceurs. La polymérisation anionique a abouti uniquement à la formation d'un polyester amorphe, tandis que la polymérisation cationique a conduit exclusivement à un polymère de structure polycétone,d'une grande stéréorégularité avec une cristallinité moyenne de 0,34. Une caractérisation fine de ces polymères a été effectuée par IRTF-ATR, RMN, TGA, DSC, GPC et diffraction desRX.

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32

Herbert, Nicola M. A. "Alkyl ketene radicals." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262948.

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33

Dziadulewicz, E. K. "Ketene dithioacetals in synthesis." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375640.

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34

Wang, Hanbin. "Synthèse et caractérisation de nouvellespolycétones aliphatiques à partir des cétènes." Phd thesis, INSA de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00973486.

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L'objectif de cette étude est de synthétiser de nouvelles architectures de polycétones aliphatiques à base de cétènes, possédant une température de fusion plus basse que le polydiméthylcétène, tout en conservant une température de dégradation élevée, afin d'élargir sa fenêtre de mise en œuvre.La synthèse du diméthylcétène et / ou de l'éthylcétène a été réalisée par pyrolyse de l'anhydride isobutyrique et/ou butyrique à 625°C sous 40 mbar. Un copolymère statistique a été d'abord synthétisé par copolymérisation entre le diméthylcétène et l'éthylcétène, par voie cationique à -78°C ; ensuite en utilisant un amorceur de Friedel-Craft, un polydiméthylcétène possédant une architecture étoilée a été obtenu. Ces deux polymères ont permis d'atteindre l'objectif initialement fixé : ils présentent un endotherme de fusion à environ 180°C, une bonne stabilité thermique similaire à celle du polydiméthylcétène (Tdégradation = 300°C), et en particulier, de très bonnes propriétés barrières à l'oxygène en milieu humide (jusqu'à 95% HR).

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35

Salter, D. P. "The synthesis and chemistry of ketene-o,o-acetal and ketene-o,s,acetals." Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381786.

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36

Pop, P. "De zorg ontketend? in ketens?" Maastricht : Maastricht : Maastricht University ; University Library, Maastricht University [Host], 2000. http://arno.unimaas.nl/show.cgi?fid=13051.

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37

Mermerian, Ara Haig 1976. "Enantioselective reactions of silyl ketene acetals and silyl ketene imines catalyzed by planar-chiral heterocycles." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28700.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004.
Vita.
Includes bibliographical references.
(cont.) imine.
The enantioselective C-acylation of cyclic silyl ketene acetals was achieved catalytically by employing planar-chiral heterocycles derived from 4-(pyrrolidino)pyridine. Key mechanistic features of this process involve activation of both the electrophile (acylating agent --> acylpyridinium) and the nucleophile (silyl ketene acetal --> enolate). This process accomodates a wide variety of aryl- and heteroaryl-substituted silyl ketene acetals, furnishing quaternary stereocenters with enantioselectivities up to 99%. Further investigation of this process revealed that acyclic disubstituted silyl ketene acetals can also participate in this nucleophile-catalyzed process, furnishing enantioselectivities up to 97%. Isomeric mixtures of silyl ketene acetals are efficiently converted into the same enantiomer of the product β-ketoester, rendering this a stereoconvergent catalytic C-acylation process. Silyl ketene imines were also shown to be suitable reaction partners in this catalytic enantioselective C-acylation reaction, affording nitriles bearing an adjacent quaternary stereocenter with enantioselectivies up to 83%. This process is also believed to proceed via activation of the electrophile (acylating agent --> acylpyridinium) and the nucleophile (silyl ketene imine --> nitrile anion), which is in direct analogy to the process developed for silyl ketene acetals. Application of this transformation to the enantioselective total synthesis of (S)-Verapamil was successfully achieved in 8 steps and 25% overall yield from commercially available 3,4-dimethoxyphenylacetonitrile. The key bond construction in this total synthesis involved enantioselective construction of the quaternary stereocenter via a catalytic C-acylation of a silyl ketene
by Ara Haig Mermerian.
Ph.D.

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38

Ogihara, Yusuke. "A Theoretical Study on the Triplet Ketene Photodissociation." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/152031.

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39

Yoshida, Suguru. "Studies on Synthetic Reactions of Ketene Dithioacetal Derivatives." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/77960.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第14581号
工博第3049号
新制||工||1454(附属図書館)
26933
UT51-2009-D293
京都大学大学院工学研究科材料化学専攻
(主査)教授大嶌幸一郎, 教授檜山爲次郎, 教授松原誠二郎
学位規則第4条第1項該当

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40

Moss, William Osburn. "Novel amino acid synthons based on ketene thioacetals." Thesis, University of Bath, 1990. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253997.

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41

Qin, Wenling <1985&gt. "Synthesis and applications of N-Metallo ketene imines." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6381/1/Qin_Wenling_Tesi.pdf.

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N-metallo ketene imines are attractive for the preparation of a wide range of organic compounds. Our research group has been engaged in the preparation and application of the N-metallo imines (SKIs). In this frame we have studied the uncatalyzed reaction of SKIs with isocyanates to give the corresponding malonamides with good yields. It has been demonstrated that the use of SKIs, instead of simple lithium anion of nitriles, is essential for the success of the reaction. A possible explanation assumes that this new reaction proceeds via a silatropism. In the course of our studies, reported in this thesis, the synthesis and the reactivity of N-silyl ketene imines in the preparation of 2,2-diaryl-3,4- dihydroxy- alcanonitrile in an uncatalyzed adol-type reaction has been performed. Our conception has been to use a chiral aldehyde to introduce asymmetric induction at the β-position and at the α-quaternary stereogenic center in the new forming diols. To achieve this goal, we used diarylacetonitrile as the substrate to form the corresponding N-trimethylsylilketene-imines to be reacted with (S)–lactic aldehyde with different protecting groups on the hydroxyl functionality. A number of 2,2-diaryl-3,4-dihydroxy-pentanenitrile were prepared with good to excellent stereo-control and satisfactory yields. Extension of this protocol to other metallo-ketene imines was performed. Accordingly, the preparation of tin ketene imines was attempted in analogy of the corresponding silyl ketene imine. The reaction of tin ketene imines with aldehydes was tested as a new tool for the synthesis of beta-hydroxynitriles starting from carbonyl compounds (aldehydes and/or ketones). Dialkyl(aryl)silyl nitriles and dialkyl(aryl)tin nitriles presents different reactivity. Finally, N-aluminium-ketene imines, as nucleophilic partner in the opening reaction of epoxides were studied. Preliminary positive results foster us to continue our studies in enlightening the scope and the limitations of this new reaction.

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42

Qin, Wenling <1985&gt. "Synthesis and applications of N-Metallo ketene imines." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6381/.

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Abstract:

N-metallo ketene imines are attractive for the preparation of a wide range of organic compounds. Our research group has been engaged in the preparation and application of the N-metallo imines (SKIs). In this frame we have studied the uncatalyzed reaction of SKIs with isocyanates to give the corresponding malonamides with good yields. It has been demonstrated that the use of SKIs, instead of simple lithium anion of nitriles, is essential for the success of the reaction. A possible explanation assumes that this new reaction proceeds via a silatropism. In the course of our studies, reported in this thesis, the synthesis and the reactivity of N-silyl ketene imines in the preparation of 2,2-diaryl-3,4- dihydroxy- alcanonitrile in an uncatalyzed adol-type reaction has been performed. Our conception has been to use a chiral aldehyde to introduce asymmetric induction at the β-position and at the α-quaternary stereogenic center in the new forming diols. To achieve this goal, we used diarylacetonitrile as the substrate to form the corresponding N-trimethylsylilketene-imines to be reacted with (S)–lactic aldehyde with different protecting groups on the hydroxyl functionality. A number of 2,2-diaryl-3,4-dihydroxy-pentanenitrile were prepared with good to excellent stereo-control and satisfactory yields. Extension of this protocol to other metallo-ketene imines was performed. Accordingly, the preparation of tin ketene imines was attempted in analogy of the corresponding silyl ketene imine. The reaction of tin ketene imines with aldehydes was tested as a new tool for the synthesis of beta-hydroxynitriles starting from carbonyl compounds (aldehydes and/or ketones). Dialkyl(aryl)silyl nitriles and dialkyl(aryl)tin nitriles presents different reactivity. Finally, N-aluminium-ketene imines, as nucleophilic partner in the opening reaction of epoxides were studied. Preliminary positive results foster us to continue our studies in enlightening the scope and the limitations of this new reaction.

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43

Hiouni, Abdelaziz. "Première synthèse des α-lithioacétals de cétène : condensation avec les dérivés carbonylés." Rouen, 1996. http://www.theses.fr/1996ROUES074.

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Pour la première fois des alpha-lithioacétals de cétène ont été obtenus. Ils ont été préparés par échange brome-lithium à partir de bromoacétals de cétène. La condensation de ces réactifs à fonction ester masquée conduit soit à des esters α, β-éthyléniques (hydrolyse acide), soit à des β-hydroxyesters (hydrolyse basique). De plus la protonation de l'intermédiaire de condensation lithié par le bromure de tertio-butyle conduit a des β-hydroxyacétals de cétène, non décrits dans la littérature. Dans certains cas la supériorité de ces lithioacétals de cétène par rapport aux réactifs classiques (Reformatsky, Wittig, Wittig-Horner-Emmons) a été montrée. Bien que possédant un groupement alcoxy en trans de l'atome de lithium les α-lithioacétals de cétène ne se transforment pas en alcoxyacétylènes par transélimination d'alcoolates de lithium contrairement aux 1-lithio-2-alcoxyéthylènes trans.

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44

Kennedy, Isaac Ato. "Taxoid synthesis: Ketene cycloadditions as a radical cyclization approach." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6815.

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Studies directed towards the synthesis of the taxane skeleton is described. The synthesis and cyclopropanation of 170 was attempted, and the preparation and base induced cyclization of gamma,delta-epoxyketone 187 and gamma,delta-epoxyester 198 examined. An unusual cycloaddition of ethyl vinyl ether to ketene carbonyls to form oxetanes was uncovered. The ketenes were generated from the cyclic diazoketones 210, 211 and 213 and the acyclic system 215. In all cases, with either Rh2(OAc)4, Pd(OAc) 2 or CuCl as catalyst, the oxetanes were the major products. Irradiation afforded the cyclobutanones 236, 237, 238 and 239, while triplet sensitized photolysis afforded both oxetane and cyclobutanone. Less electron rich olefins followed literature precedent for metal catalyzed decomposition to yield cyclopropanes. These features are consistent with a zwitterionic intermediate such as 247 (Scheme i illustrates these general features). The preparation of the key radical cyclization precursor 282 and related compounds, 289 and 305 containing the taxol A and C ring models from enone 202 and subsequent radical cyclization to the taxane skeleton 284a are also described.* *Please refer to dissertation for diagrams.

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45

Zhou, Ya Jun. "The effect of ageing on alkyl ketene dimer sizing." Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337537.

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46

Scott, Robert John. "Studies of the iron(III) mediated oxidative ring opening of cyclopropyl ethers and acetals for radical cyclisations." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327495.

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47

Roden, Peter John. "The gas-phase oxidation of unsaturated compounds at elevated temperatures." Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338552.

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48

Roseblade, Stephen. "Intramolecular asymmetric nitrone cycloadditions in the synthesis of Î² amino acids." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251146.

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49

TCHERTCHI, AN SYLVIE. "Controle de la stéréochimie en série acyclique : application à la synthèse de la zwittermycine A." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10267.

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La zwittermycine a est un aminopolyol possedant d'importantes proprietes antibiotiques et antifongiques. Elle est composee d'une partie uree-amide derivee d'un aminoacide non naturel proteique, l'albizziine, et d'une partie diaminopentol. L'approche synthetique convergente envisagee utilise un synthon chiral commun derive de la l-serine, l'aldehyde de garner. Au cours de ce travail, nous avons realise la synthese des deux enantiomeres de la partie uree-amide sous une forme protegee. Dans un deuxieme temps, deux strategies pour la synthese de la partie diaminopentol ont ete mises en oeuvre. La premiere, mettant en jeu l'utilisation de derives enethiolates thiocarbonyles, conduit a des -hydroxydithioesters avec des selectivites seulement moyennes. Elle a toutefois permis de mettre au point une methode generale de synthese d'hydroxydithioacetals de cetene a partir d'aldehydes. La seconde strategie implique la creation stereocontrolee de trois centres asymetriques par des reactions d'allylmetallation, de dihydroxylation de sharpless et de condensation de 3-lithiopropiolates d'alkyle sur des nitrones. Une etude de la diastereoselectivite de cette derniere methodologie a ete menee avec diverses nitrones -chirales. Cette deuxieme approche nous a permis de realiser la synthese d'un intermediaire sous forme protegee, precurseur de la partie diaminopentol, avec un rendement global de 40% a partir de l'aldehyde de garner.

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50

Asbroek, Anna Laura Margaretha Antoinette ten. "Allele specific inhibition a novel approach to cancer therapy /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/61441.

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