Journal articles: 'Organic Chemistry Reactions - Selectivity'

1

Kawase, Misa, Tomohiro Shibata, Shouhei Masuu, Masaki Yamaguchi, Yoshimasa Matsumura, Osamu Shimomura, and Atsushi Ohtaka. "Expression of Reaction Selectivity and the Substituent Effect in Ullmann, Suzuki, Hiyama, and Allylic Arylation Reactions Caused by Reducing Catalyst Loading." Catalysts 13, no. 7 (July 17, 2023): 1115. http://dx.doi.org/10.3390/catal13071115.

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The control of stereo-, regio-, and chemo-selectivity in transition-metal-catalyzed coupling reactions is a key topic in organic synthesis. Several methods for controlling selectivity have been reported thus far. On the other hand, the reduction of catalyst loading during reactions is one of the most important issues in organic synthesis from the standpoint of green sustainable chemistry. As another advantage of reducing catalyst loading, the expression of reaction selectivity and the substituent effect caused by the reduction of catalyst loading to the parts-per-million (ppm) level in various catalytic reactions is presented herein.

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Tung, Chen-Ho, Li-Zhu Wu, Li-Ping Zhang, Hong-Ru Li, Xiu-Yu Yi, Kai Song, Ming Xu, et al. "Microreactor-controlled selectivity in organic photochemical reactions." Pure and Applied Chemistry 72, no. 12 (January 1, 2000): 2289–98. http://dx.doi.org/10.1351/pac200072122289.

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Molecular-sieve zeolites, Nafion membranes, low-density polyethylene films, and mixed surfactant vesicles have been used as microreactors to carry out organic photochemical reactions. The photo-cycloadditions of diaryl compounds with long flexible chains included in NaY zeolite or low-density polyethylene films yield intramolecular photocyclomers to the exclusion of intermolecular products. The photosensitized oxidation of alkenes included in pentasil zeolites or Nafion membranes or vesicles can be directed selectively toward either the singlet oxygen-mediated or the superoxide radical anion-mediated products by controlling the status and location of the substrate and sensitizer molecules in the reaction media. The photo-Fries rearrangement of phenyl phenylacetates included within NaY and pentasil zeolites or Nafion membranes gives either ortho-hydroxyphenones or decarbonylation products depending on the size/shape of the microreactors and the substrate molecules. All these results demonstrate the utility of microreactors to control the product selectivity in organic photochemical reactions.

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Chao, T. M., Jon Baker, W. J. Hehre, and S. D. Kahn. "Models for selectivity in organic reactions." Pure and Applied Chemistry 63, no. 2 (January 1, 1991): 283–88. http://dx.doi.org/10.1351/pac199163020283.

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Lee, Sanha, and Jonathan M. Goodman. "VRAI-selectivity: calculation of selectivity beyond transition state theory." Organic & Biomolecular Chemistry 19, no. 17 (2021): 3940–47. http://dx.doi.org/10.1039/d1ob00234a.

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Guo, Richard, Romelo Gibe, and James R. Green. "Mono- and disubstitutions of (hepta-2,5-diyne-1,7-diol) bis(dicobalt) derivatives Selectivity in Nicholas reactions." Canadian Journal of Chemistry 82, no. 2 (February 1, 2004): 366–74. http://dx.doi.org/10.1139/v03-209.

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Bis(hexacarbonyldicobalt) complexes of benzyl ether methyl ether or benzyl ether acetate derivatives of hepta-2,5-diyne-1,7-diols undergo selective Lewis-acid-mediated Nicholas reactions with enol silanes, silyl ketene acetals, and allylstannanes, preferentially replacing the methyl ether or acetate function. Hydride nucleophiles are similarly incorporated selectively using a benzyl ether alcohol derivative. Subsequent Nicholas reaction at the benzyloxy-bearing site may be accomplished with an identical or a different nucleophile, affording skipped 1,4-diyne-Co4(CO)12 complexes. In instances of lower selectivity for monosubstitution reactions with benzyl ethers, reverting to the use of a menthyl ether methyl ether complex gives much improved selectivity for methyl ether substitution.Key words: cobalt alkyne complexes, Nicholas reaction, Lewis acids, 1,4-diynes.

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Venkatesham, Akkaladevi, Sambasiva Rao Pillalamarri, Flore De Wit, Eveline Lescrinier, Zeger Debyser, and Arthur Van Aerschot. "Propargylated Purine Deoxynucleosides: New Tools for Fluorescence Imaging Strategies." Molecules 24, no. 3 (January 28, 2019): 468. http://dx.doi.org/10.3390/molecules24030468.

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In vivo imaging of biological processes is an important asset of modern cell biology. Selectively reacting fluorophores herein are an important tool and click chemistry reactions take a large share in these events. 5-Ethynyl-2′-deoxyuridine (EdU) is well known for visualizing DNA replication, but does not show any selectivity for incorporation into DNA. Striving for specific visualization of virus replication, in particular HIV replication, a series of propargylated purine deoxynucleosides were prepared aiming for selective incorporation by HIV reverse transcriptase (RT). We here report on the synthesis and preliminary biological effects (cellular toxicity, HIV inhibitory effects, and feasibility of the click reaction) of these nucleoside analogues.

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Cooper, Alasdair K., Paul M. Burton, and David J. Nelson. "Nickel versus Palladium in Cross-Coupling Catalysis: On the Role of Substrate Coordination to Zerovalent Metal Complexes." Synthesis 52, no. 04 (December 19, 2019): 565–73. http://dx.doi.org/10.1055/s-0039-1690045.

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A detailed comparison of the effect of coordinating functional groups on the performance of Suzuki–Miyaura reactions catalysed by nickel and palladium is reported, using competition experiments, robustness screening, and density functional theory calculations. Nickel can interact with a variety of functional groups, which manifests as selectivity in competitive cross-coupling reactions. The presence of these functional groups on exogenous additives has effects on cross-coupling reactions that range from a slight improvement in yield to the complete cessation of the reaction. In contrast, palladium does not interact sufficiently strongly with these functional groups to induce selectivity in cross-coupling reactions; the selectivity of palladium-catalysed cross-coupling reactions is predominantly governed by aryl halide electronic properties.

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8

Shaik, Sason S. "Intrinsic selectivity and its geometric significance in SN2 reactions." Canadian Journal of Chemistry 64, no. 1 (January 1, 1986): 96–99. http://dx.doi.org/10.1139/v86-016.

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An intrinsic selectivity is defined for identity SN2 reactions (X− + RX → XR + X−). This selectivity parameter is shown to yield information about: (a) the average looseness of the TS geometry in a reaction series; and (b) the sensitivity of the reaction series to geometric loosening.

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Ormazábal-Toledo, Rodrigo, and Renato Contreras. "Philicity and Fugality Scales for Organic Reactions." Advances in Chemistry 2014 (August 18, 2014): 1–13. http://dx.doi.org/10.1155/2014/541547.

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Theoretical scales of reactivity and selectivity are important tools to explain and to predict reactivity patterns, including reaction mechanisms. The main achievement of these efforts has been the incorporation of such concepts in advanced texts of organic chemistry. In this way, the modern organic chemistry language has become more quantitative, making the classification of organic reactions an easier task. The reactivity scales are also useful to set up a number of empirical rules that help in rationalizing and in some cases anticipating the possible reaction mechanisms that can be operative in a given organic reaction. In this review, we intend to give a brief but complete account on this matter, introducing the conceptual basis that leads to the definition of reactivity indices amenable to build up quantitative models of reactivity in organic reactions. The emphasis is put on two basic concepts describing electron-rich and electron-deficient systems, namely, nucleophile and electrophiles. We then show that the regional nucleophilicity and electrophilicity become the natural descriptors of electrofugality and nucleofugality, respectively. In this way, we obtain a closed body of concepts that suffices to describe electron releasing and electron accepting molecules together with the description of permanent and leaving groups in addition, nucleophilic substitution and elimination reactions.

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Clennan, Edward L., and Xiangning Chen. "Geminal selectivity in singlet oxygen reactions." Journal of Organic Chemistry 53, no. 13 (June 1988): 3124–25. http://dx.doi.org/10.1021/jo00248a044.

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11

Aljuboori, Sahar Balkat, Nedaa Abdulhameed Abdulrahim, Shuhad Yassen, and Heba Hashim Khaleel. "Organic Synthesis under Solvent-free Condition (Green Chemistry): A Mini Literature Review." Al-Rafidain Journal of Medical Sciences ( ISSN: 2789-3219 ) 3 (December 17, 2022): 109–15. http://dx.doi.org/10.54133/ajms.v3i.94.

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Solvents are important components in the pharmaceutical and chemical industries, and they are increasingly being used in catalytic reactions. Solvents have a significant influence on the kinetics and thermodynamics of reactions, and they can significantly change product selectivity. Solvents can influence product selectivity, conversion rates, and reaction rates. However, solvents have received a lot of attention in the field of green chemistry. This is due to the large amount of solvent that is frequently used in a process or formulation, particularly during the purification steps. However, neither the solvent nor the active ingredient in a formulation is directly responsible for the reaction product's composition. Because these characteristics have little bearing on how well or quickly the system in which the solvent is applied works, it appears unnecessary to use toxic, combustible, or environmentally hazardous solvents. However, the beneficial properties of the solvent required for the application are strongly linked to these unfortunate side effects of solvent use. Distillation can be used to recover and purify solvents because they are volatile; however, this process can produce unwanted air pollutants and be hazardous to workers during exposure. .

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12

Charlton, James L., Guy L. Plourde, and Glenn H. Penner. "Asymmetric induction in Diels–Alder reactions of α-alkoxyorthoquinodimethanes." Canadian Journal of Chemistry 67, no. 6 (June 1, 1989): 1010–14. http://dx.doi.org/10.1139/v89-153.

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It has been shown that dienophiles cycloadd selectively to one face of o-quinodimethanes (o-QDMs) bearing chiral α-alkoxy groups. The face selectivity (diastereoselectivity) increases for the series of chiral groups -OCH(Ph)CH3, -OCH(Ph)CH(CH3)2, and -OCH(Ph)C(CH3)3. A similar effect on the face selectivity of the Diels–Alder reactions of chiral alkoxy vinyl ethers for the same series of chiral groups has been noted previously by others. A mechanism has been proposed to explain the face selectivity in the cycloaddition reactions of the alkoxy o-QDMs. Abinitio molecular orbital calculations with geometry optimization on vinyl 1-phenylethyl ether to determine its lowest energy conformations support the proposed mechanism. The absolute stereochemistries of the o-QDM cycloadducts have been determined to verify the predictions of the model. Keywords: o-quinodimethanes, asymmetric, Diels–Alder, cycloaddition.

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Tang, Christina, and Bridget T. McInnes. "Cascade Processes with Micellar Reaction Media: Recent Advances and Future Directions." Molecules 27, no. 17 (August 31, 2022): 5611. http://dx.doi.org/10.3390/molecules27175611.

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Reducing the use of solvents is an important aim of green chemistry. Using micelles self-assembled from amphiphilic molecules dispersed in water (considered a green solvent) has facilitated reactions of organic compounds. When performing reactions in micelles, the hydrophobic effect can considerably accelerate apparent reaction rates, as well as enhance selectivity. Here, we review micellar reaction media and their potential role in sustainable chemical production. The focus of this review is applications of engineered amphiphilic systems for reactions (surface-active ionic liquids, designer surfactants, and block copolymers) as reaction media. Micelles are a versatile platform for performing a large array of organic chemistries using water as the bulk solvent. Building on this foundation, synthetic sequences combining several reaction steps in one pot have been developed. Telescoping multiple reactions can reduce solvent waste by limiting the volume of solvents, as well as eliminating purification processes. Thus, in particular, we review recent advances in “one-pot” multistep reactions achieved using micellar reaction media with potential applications in medicinal chemistry and agrochemistry. Photocatalyzed reactions in micellar reaction media are also discussed. In addition to the use of micelles, we emphasize the process (steps to isolate the product and reuse the catalyst).

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14

Ghashghaei, Ouldouz, Francesca Seghetti, and Rodolfo Lavilla. "Selectivity in multiple multicomponent reactions: types and synthetic applications." Beilstein Journal of Organic Chemistry 15 (February 21, 2019): 521–34. http://dx.doi.org/10.3762/bjoc.15.46.

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Multiple multicomponent reactions reach an unparalleled level of connectivity, leading to highly complex adducts. Usually, only one type of transformation involving the same set of reactants takes place. However, in some occasions this is not the case. Selectivity issues then arise, and different scenarios are analyzed. The structural pattern of the reactants, the reaction design and the experimental conditions are the critical factors dictating selectivity in these processes.

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Nihala, Rasheed, Kalathingal Nasreen Hisana, C. M. A. Afsina, and Gopinathan Anilkumar. "Applications of iron pincer complexes in hydrosilylation reactions." RSC Advances 12, no. 37 (2022): 24339–61. http://dx.doi.org/10.1039/d2ra04239h.

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Iron pincer complexes are efficient in catalyzing various organic reactions with excellent selectivity and functional group tolerance at moderate reaction conditions. This review focuses on the applications of iron pincer complexes in hydrosilylation reactions.

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16

Nayak, Yogeesha N., Swarnagowri Nayak, Y. F. Nadaf, Nitinkumar S. Shetty, and Santosh L. Gaonkar. "Zeolite Catalyzed Friedel-Crafts Reactions: A Review." Letters in Organic Chemistry 17, no. 7 (July 7, 2020): 491–506. http://dx.doi.org/10.2174/1570178616666190807101012.

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Friedel-Crafts reaction is one of the most useful synthetic tools in organic chemistry, mainly in the synthesis of aromatic ketones. The active catalysts for this reaction are modified zeolites and are preferable catalysts when shape selectivity affects the formation of the expected product. In this review, our aim is to corroborate recent literature available on zeolite catalyzed Friedel-Crafts alkylation and acylation reaction.

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17

Kaur, Navjeet. "Photochemical Reactions for the Synthesis of Six-Membered O-Heterocycles." Current Organic Synthesis 15, no. 3 (April 27, 2018): 298–320. http://dx.doi.org/10.2174/1570179414666171011160355.

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Background: The chemists have been interested in light as an energy source to induce chemical reactions since the beginning of the scientific chemistry. This review summarizes the chemistry of photochemical reactions with emphasis of their synthetic applications. The organic photochemical reactions avoid the polluting or toxic reagents and therefore offer perspectives for sustainable processes and green chemistry. In summary, this review article describes the synthesis of a number of six-membered O-heterocycles. Objective: Photochemistry is indeed a great tool synthetic chemists have at their disposal. The formation of byproducts was diminished under photochemical substrate activation that usually occurred without additional reagents. Photochemical irradiation is becoming more interesting day by day because of easy purification of the products as well as green chemistry. Conclusion: This review article represents the high applicability of photochemical reactions for organic synthesis and research activities in organic photochemistry. The synthesis of heterocyclic molecules has been outlined in this review. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. Photochemistry can be used to prepare a number of heterocycles selectively, efficiently and in high yield.

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Rahmanivahid, Behgam, Maria Pinilla-de Dios, Mohammad Haghighi, and Rafael Luque. "Mechanochemical Synthesis of CuO/MgAl2O4 and MgFe2O4 Spinels for Vanillin Production from Isoeugenol and Vanillyl Alcohol." Molecules 24, no. 14 (July 17, 2019): 2597. http://dx.doi.org/10.3390/molecules24142597.

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CuO/MgAl2O4 and CuO/MgFe2O4 catalysts were successfully synthesized with the use of spinel supports by a very simple and low-cost mechanochemical method. High-speed ball-milling was used to synthesize these catalyst supports for the first time. Materials were subsequently characterized by using XRD, FESEM, TEM, EDS-Dot mapping, XPS, BET-BJH, and Magnetic Susceptibility to investigate the physical-chemical characteristics of the catalysts. Acidity evaluation results indicated that the catalyst with the Mg-Al spinel support had more acid sites. XRD results showed a successful synthesis of the catalysts with large crystal sizes. Both catalysts were used in isoeugenol oxidation and vanillyl alcohol to vanillin reactions, with the CuO/MgAl2O4 showing optimum results. This catalyst provided 67% conversion (74% selectivity) after 2 h and this value improved to 81% (selectivity 100%) with the second reaction after 8 h. The CuO/MgFe2O4 catalyst in the first reaction after five hours revealed 53% conversion (47% selectivity) and after eight hours with the second reaction, the conversion value improved to 64% (100% selectivity). In terms of reusability, CuO/MgAl2O4 showed better results than the CuO/MgFe2O4 catalyst, for both reactions.

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Langer, Peter, Stefan Jopp, Marko Liesegang, Peter Ehlers, Eva Frank, Gyula Schneider, János Wölfling, and Alexander Villinger. "Palladium-Catalysed Sonogashira Reactions of 16-(Hydroxymethylidene)-3-methoxy-α-estrone." Synlett 28, no. 19 (August 17, 2017): 2647–49. http://dx.doi.org/10.1055/s-0036-1588537.

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Sonogashira reactions of steroids have been studied. The reaction of α-estron-16-methylidenyloxy triflate with various alkynes afforded novel alkynylvinylidene steroids. The reactions proceeded in good to quantitative yields, with excellent E-selectivity and with a broad synthetic scope.

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Gulati, Shivani, Stephy Elza John, and Nagula Shankaraiah. "Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects." Beilstein Journal of Organic Chemistry 17 (April 19, 2021): 819–65. http://dx.doi.org/10.3762/bjoc.17.71.

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Microwave-assisted (MWA) multicomponent reactions (MCRs) have successfully emerged as one of the useful tools in the synthesis of biologically relevant heterocycles. These reactions are strategically employed for the generation of a variety of heterocycles along with multiple point diversifications. Over the last few decades classical MCRs such as Ugi, Biginelli, etc. have witnessed enhanced yield and efficiency with microwave assistance. The highlights of MWA-MCRs are high yields, reduced reaction time, selectivity, atom economy and simpler purification techniques, such an approach can accelerate the drug discovery process. The present review focuses on the recent advances in MWA-MCRs and their mechanistic insights over the past decade and shed light on its advantage over the conventional approach.

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Cimarelli, Cristina. "Multicomponent Reactions." Molecules 24, no. 13 (June 27, 2019): 2372. http://dx.doi.org/10.3390/molecules24132372.

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Multicomponent Reactions appear to be ideal for any form of synthesis, because of their numerous advantages in terms of sustainability and selectivity in building up complex molecular architectures, with high molecular diversity. This Special Issue collects seven contributions which expand our knowledge about Multicomponent Reactions, providing a good overview about innovative reactivities and applications.

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Chen, Hong-Yu, Meng Gou, and Jiao-Bing Wang. "De novo endo-functionalized organic cages as cooperative multi-hydrogen-bond-donating catalysts." Chemical Communications 53, no. 25 (2017): 3524–26. http://dx.doi.org/10.1039/c7cc00938k.

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Two endo-functionalized organic cages as oxyanion hole mimics were achieved via dynamic covalent chemistry, which exhibit good size selectivity, catalytic activity and broad substrate scopes for Friedel–Crafts reactions.

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Wong, Wing-Leung, and Kwok-Yin Wong. "Recent development in functionalized ionic liquids as reaction media and promoters." Canadian Journal of Chemistry 90, no. 1 (January 2012): 1–16. http://dx.doi.org/10.1139/v11-110.

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The recent development in the use of functionalized ionic liquids as both reaction media and promoters is reviewed. Ionic liquids designed with special functionality can enhance the reaction rate, selectivity, and productivity in various chemical reactions. In this context, some important chemical reactions involving C–C, C–O, C–N, and C–S bond formation in functionalized ionic liquids are discussed. These functionalized ionic liquids were found to provide distinct advantages over conventional organic solvents in these catalytic reactions.

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Ju, Longxin, Gang Li, and Hongxian Luo. "Catalytic Synthesis of Methacrolein via the Condensation of Formaldehyde and Propionaldehyde with L-Proline Intercalated Layered Double Hydroxides." Catalysts 12, no. 1 (December 31, 2021): 42. http://dx.doi.org/10.3390/catal12010042.

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Aldol condensation reactions are very important C–C coupling reactions in organic chemistry. In this study, the catalytic performance of layered double hydroxides (LDHs) in the aldol condensation reaction of formaldehyde (FA) and propionaldehyde (PA) was investigated. The MxAl-LDHs (denoted as re-MxAl–LDHs; M = Ca and Mg; X = 2–4), as heterogeneous basic catalysts toward the aldol condensation reaction, were prepared via a two-step procedure. The catalyst exhibited a high PA conversion (82.59%), but the methacrolein (MAL) selectivity was only 36.01% due to the limitation of the alkali-catalyzed mechanism. On this basis, the direct intercalation of L-proline into LDHs also has been investigated. The influences of several operating conditions, including the temperature, reaction time, and substrate content, on the reaction results were systematically studied, and the optimized reaction conditions were obtained. The optimized Mg3Al–Pro-LDHs catalyst exhibited a much higher MAL selectivity than those of re-MgxAl–LDHs.

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Sharma, Sachin, Gaurav Joshi, Sourav Kalra, Sandeep Singh, and Raj Kumar. "Synthetic Versus Enzymatic Pictet-Spengler Reaction: An Overview." Current Organic Synthesis 15, no. 7 (October 16, 2018): 924–39. http://dx.doi.org/10.2174/1570179415666180613084014.

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Background: Pictet-Spengler reactions is an irreplaceable part of cyclization reaction leading to the formation of indispensable heterocyclic moieties including imidazole, benzoxazole, pyrrole, indole and others having immense biological and chemical significance. Researchers have explored this reaction using different types of catalysts and reactions conditions (including solvents, acids, etc.) to ensure the better selectivity, less reaction time and high product yields. A total of five Pictet-Spenglerases have been discovered from various sources including plants, animals, fungi, and microbes, and are responsible for the synthesis of various important alkaloids of biological medicinal importance. Objective: The present review is a strenuous effort to assemble information mainly focusing on synthetic as well as biological Pictet-Spengler reactions catalysed by enzymes called Pictet-Spenglerase. Conclusion: In the present review, the recent advances in the PS-mediated synthesis of diverse heterocycles such as tetrahydroisoquinoline, tetrahydro-β-carbolines, tetrahydroimidazopyridines and other fused heterocycles via chemical as well as enzymatic pathways have been covered. The compounds find their scope as medicinal agents for the treatment of cancer, tuberculosis, bacterial infection, leishmanial, etc. The compilation is expected to provide a mechanistic insight to chemists to enhance the reaction condition, yields and another parameter to ensure the safe and inexpensive reaction conditions considering the “Green-Concept” of chemistry.

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Protti, Stefano, Davide Ravelli, and Maurizio Fagnoni. "Wavelength dependence and wavelength selectivity in photochemical reactions." Photochemical & Photobiological Sciences 18, no. 9 (2019): 2094–101. http://dx.doi.org/10.1039/c8pp00512e.

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27

Bueno, Maria P., Carlos Cativiela, José A. Mayoral, Alberto Avenoza, Paula Charro, Miguel A. Roy, and José M. Andres. "Natural amino acids as chiral auxiliaries in asymmetric Diels–Alder reactions." Canadian Journal of Chemistry 66, no. 11 (November 1, 1988): 2826–29. http://dx.doi.org/10.1139/v88-437.

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To test whether α-amino acids can be efficient chiral auxiliaries in asymmetric Diels–Alder reactions, the chiral dienophile N-acryloyl-L-phenylalanine methyl ester was made to react with cyclopentadiene. Diastereofacial selectivity is to a great extent dependent on the Lewis acid used to promote the reaction; whereas moderate excesses of the (1R,2R)-cycloadduct were achieved with AlCl3, the reaction did not show diastereofacial selectivity when titanium catalysts were used. Moreover, with Ti(iPrO)4 a transesterification reaction, which leads to the isopropyl ester and competes with the Diels–Alder reaction, was observed. In spite of the structural similarity of this dienophile to the acrylate of (S)-ethyl lactate, it behaved very differently in the titanium-catalyzed reactions.

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Dreier, Anna-Lena, Andrej V. Matsnev, Joseph S. Thrasher, and Günter Haufe. "Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ6-sulfanyl)acetic acid esters with aldehydes." Beilstein Journal of Organic Chemistry 14 (February 8, 2018): 373–80. http://dx.doi.org/10.3762/bjoc.14.25.

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Aldol reactions belong to the most frequently used C–C bond forming transformations utilized particularly for the construction of complex structures. The selectivity of these reactions depends on the geometry of the intermediate enolates. Here, we have reacted octyl pentafluoro-λ6-sulfanylacetate with substituted benzaldehydes and acetaldehyde under the conditions of the silicon-mediated Mukaiyama aldol reaction. The transformations proceeded with high diastereoselectivity. In case of benzaldehydes with electron-withdrawing substituents in the para-position, syn-α-SF5-β-hydroxyalkanoic acid esters were produced. The reaction was also successful with meta-substituted benzaldehydes and o-fluorobenzaldehyde. In contrast, p-methyl-, p-methoxy-, and p-ethoxybenzaldehydes led selectively to aldol condensation products with (E)-configured double bonds in 30–40% yields. In preliminary experiments with an SF5-substituted acetic acid morpholide and p-nitrobenzaldehyde, a low amount of an aldol product was formed under similar conditions.

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Sahoo, Biswa Mohan, and Bimal Krishna Banik. "Organocatalysis: Trends of Drug Synthesis in Medicinal Chemistry." Current Organocatalysis 6, no. 2 (June 24, 2019): 92–105. http://dx.doi.org/10.2174/2213337206666190405144423.

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Background:The continuous increase in challenges associated with the effective treatment of life threatening diseases influences the development of drug therapies with suitable physicochemical properties, efficiency and selectivity. So, organocatalysis is a potential synthetic tool which is accelerating the development of new drug molecules.Methods:Organocatalysis reactions can be carried out at lower temperatures and in milder pH conditions as compared to metal based catalysed reactions. Due to ready availability of catalysts, stability, purity, low toxicity and easy in handling of the chemical reactions, it has become an attractive technique to synthesise complex molecules with diverse structures. Here, the impact of various catalysts in organic synthesis with methods is discussed.Results:Organic catalysts are used widely in various chemical reactions such as Michael Addition, aldol reaction, Diels-Alder reactions and Knoevenagal reactions. It was observed that the use of organocatalyst results in the formation of stereo active molecules with diverse biological activities.Conclusion:This review also focuses on the various scopes and limitations of organocatalytic reactions in the production of medicinally useful drug molecules. Organocatalysts possess several advantages over traditional metal catalysts because they are non-toxic, readily available, stable, efficient, and easy to handle which involves environmentally friendly reaction.

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Bailey, David, and Vance E. Williams. "Wavelength-Dependent Selectivity in [4 + 4]-Cycloaddition Reactions." Journal of Organic Chemistry 71, no. 15 (July 2006): 5778–80. http://dx.doi.org/10.1021/jo060838q.

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Zahra, Fatima Tuz, Aamer Saeed, Khansa Mumtaz, and Fernando Albericio. "Tropylium Ion, an Intriguing Moiety in Organic Chemistry." Molecules 28, no. 10 (May 15, 2023): 4095. http://dx.doi.org/10.3390/molecules28104095.

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The tropylium ion is a non-benzenoid aromatic species that works as a catalyst. This chemical entity brings about a large number of organic transformations, such as hydroboration reactions, ring contraction, the trapping of enolates, oxidative functionalization, metathesis, insertion, acetalization, and trans-acetalization reactions. The tropylium ion also functions as a coupling reagent in synthetic reactions. This cation’s versatility can be seen in its role in the synthesis of macrocyclic compounds and cage structures. Bearing a charge, the tropylium ion is more prone to nucleophilic/electrophilic reactions than neutral benzenoid equivalents. This ability enables it to assist in a variety of chemical reactions. The primary purpose of using tropylium ions in organic reactions is to replace transition metals in catalysis chemistry. It outperforms transition-metal catalysts in terms of its yield, moderate conditions, non-toxic byproducts, functional group tolerance, selectivity, and ease of handling. Furthermore, the tropylium ion is simple to synthesize in the laboratory. The current review incorporates the literature reported from 1950 to 2021; however, the last two decades have witnessed a phenomenal upsurge in the utilization of the tropylium ion in the facilitation of organic conversions. The importance of the tropylium ion as an environmentally safe catalyst in synthesis and a comprehensive summary of some important reactions catalyzed via tropylium cations are described.

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Verhelst, Steven H. L., Kimberly M. Bonger, and Lianne I. Willems. "Bioorthogonal Reactions in Activity-Based Protein Profiling." Molecules 25, no. 24 (December 18, 2020): 5994. http://dx.doi.org/10.3390/molecules25245994.

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Activity-based protein profiling (ABPP) is a powerful technique to label and detect active enzyme species within cell lysates, cells, or whole animals. In the last two decades, a wide variety of applications and experimental read-out techniques have been pursued in order to increase our understanding of physiological and pathological processes, to identify novel drug targets, to evaluate selectivity of drugs, and to image probe targets in cells. Bioorthogonal chemistry has substantially contributed to the field of ABPP, as it allows the introduction of tags, which may be bulky or have unfavorable physicochemical properties, at a late stage in the experiment. In this review, we give an overview of the bioorthogonal reactions that have been implemented in ABPP, provide examples of applications of bioorthogonal chemistry in ABPP, and share some thoughts on future directions.

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Quintard, Jean-Paul, Gilles Dumartin, Bernard Elissondo, Alain Rahm, and Michel Pereyre. "Selectivity in reactions involving α-alkoxyallyltributyltins." Tetrahedron 45, no. 4 (January 1989): 1017–28. http://dx.doi.org/10.1016/0040-4020(89)80013-4.

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Rejman, Dominik, Šárka Králíková, Zdeněk Točík, Radek Liboska, and Ivan Rosenberg. "Selective Cleavage of O-(Dimethoxytrityl) Protecting Group with Sodium Periodate." Collection of Czechoslovak Chemical Communications 67, no. 4 (2002): 502–8. http://dx.doi.org/10.1135/cccc20020502.

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Sodium periodate in aqueous organic solvents selectively removes, under mild reaction conditions, the O-(dimethoxytrityl) protecting group. Selectivity of the cleavage was studied using the nucleoside derivatives protected by various types of groups commonly used in nucleoside and nucleotide chemistry.

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Coates, Greg, Feriel Rekhroukh, and Mark R. Crimmin. "Breaking Carbon–Fluorine Bonds with Main Group Nucleophiles." Synlett 30, no. 20 (November 12, 2019): 2233–46. http://dx.doi.org/10.1055/s-0039-1690738.

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In this Account we describe a series of new reactions that we, and others, have reported that involve the transformation of C–F bonds into C–Mg, C–Al, C–Si, C–Fe and C–Zn bonds. We focus on the use of highly reactive main group nucleophiles and discuss aspects of reaction scope, selectivity and mechanism.1 Introduction1.1 The Fluorocarbon Industry and Sustainability1.2 Production of Fluorocarbons1.3 Properties of Fluorocarbons1.4 Our Work2 Results and Discussion2.1 Low-Valent Main Group Compounds2.1.1 Reactions with Fluoroarenes2.1.2 Reactions with Fluoroalkanes2.1.3 Reactions with Fluoroalkenes2.2 Main Group Nucleophiles (M1–M2)2.2.1 Reactions of M1–M2 Nucleophiles with Fluoroarenes2.2.2 Reactions of M1–M2 Nucleophiles with Fluoroalkanes2.2.3 Reactions of M1–M2 Nucleophiles with Fluoroalkenes3 Summary and Perspective

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Zanatta, Nilo, Mateus Mittersteiner, Estefania C. Aquino, Tuvshinjargal Budragchaa, Ludger A. Wessjohann, Helio G. Bonacorso, and Marcos A. P. Martins. "Synthesis of Methylene-Bridged Trifluoromethyl Azoles Using 5-(1,2,3-Triazol-1-yl)enones." Synthesis 54, no. 02 (October 6, 2021): 439–50. http://dx.doi.org/10.1055/s-0040-1719837.

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AbstractA protocol for synthesizing triazole-containing pyrazolines and pyrazoles selectively using trifluoromethylated 5-(1,2,3-triazol-1-yl)enones as starting materials, is reported. The selectivity of the reaction was controlled by the nature of the hydrazine or derivative used: free hydrazines furnished the 1,5-regiosiomer exclusively in yields up to 98%, whereas protected hydrazines provided the 1,3-regioisomer in yields up to 77%. To demonstrate the synthetic versatility of the triazole-based enone, reactions with other unsymmetrical dinucleophiles (hydroxylamine hydrochloride and S-methyl isothiourea sulfates) allowed the selective preparation of triazole-containing isoxazoline and pyrimidine rings.

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37

Ward, Dale E., and Yuanzhu Gai. "Lewis acid mediated Diels–Alder reactions of 2H-thiopyrans." Canadian Journal of Chemistry 70, no. 10 (October 1, 1992): 2627–34. http://dx.doi.org/10.1139/v92-331.

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Lewis acid mediated Diels–Alder reactions of 2H-thiopyrans with acrylate, crotonate, and methacrylate dienophiles have been investigated. Modest to good yields of predominantly exo adducts are obtained with 4-substituted 2H-thiopyrans. With 5-substituted 2H-thiopyrans, high endo selectivity is observed. No adducts were produced with methacrylate dienophiles. Relative to the thermal reactions, the exo selectivity is enhanced in the presence of Lewis acids. Unusually high exo selectivity is observed using "wet" Et2AlCl as the promoter.

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Yakubov, Shahboz, and Joshua P. Barham. "Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis." Beilstein Journal of Organic Chemistry 16 (September 3, 2020): 2151–92. http://dx.doi.org/10.3762/bjoc.16.183.

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The importance of fluorinated products in pharmaceutical and medicinal chemistry has necessitated the development of synthetic fluorination methods, of which direct C–H fluorination is among the most powerful. Despite the challenges and limitations associated with the direct fluorination of unactivated C–H bonds, appreciable advancements in manipulating the selectivity and reactivity have been made, especially via transition metal catalysis and photochemistry. Where transition metal catalysis provides one strategy for C–H bond activation, transition-metal-free photochemical C–H fluorination can provide a complementary selectivity via a radical mechanism that proceeds under milder conditions than thermal radical activation methods. One exciting development in C–F bond formation is the use of small-molecule photosensitizers, allowing the reactions i) to proceed under mild conditions, ii) to be user-friendly, iii) to be cost-effective and iv) to be more amenable to scalability than typical photoredox-catalyzed methods. In this review, we highlight photosensitized C–H fluorination as a recent strategy for the direct and remote activation of C–H (especially C(sp3)–H) bonds. To guide the readers, we present the developing mechanistic understandings of these reactions and exemplify concepts to assist the future planning of reactions.

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Castagnolo, Daniele, and Kate Lauder. "Photo-Biocatalytic Cascades for the Synthesis of Volatile Sulfur Compounds and Chemical Building Blocks." Synlett 31, no. 08 (January 10, 2020): 737–44. http://dx.doi.org/10.1055/s-0039-1690784.

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Biocatalysis is a branch of catalysis that exploits enzymes to perform highly stereoselective chemical transformations under mild and sustainable conditions. This Synpact highlights how biocatalysis can be used in the synthesis of chiral 1,3-mercaptoalkanols, an important class of compounds responsible for the flavours and aromas of many foods and beverages. The identification of two ketoreductase (KRED) enzymes able to reduce prochiral ketone precursors enantioselectively to 1,3-mercaptoalkanols bearing a C–O stereocentre is presented. In addition, the combination of a photocatalytic thia-Michael reaction to access prochiral ketones with subsequent KRED-biocatalysed reduction in a one-pot cascade is presented. Photo-biocatalysed cascades represent one of the new and most intriguing challenges in synthetic chemistry, because the combination of different catalytic methodologies in domino processes offers unique opportunities to outperform sequential reactions with a high degree of selectivity and the avoidance of the need to isolate reaction intermediates.1 Introduction2 Biocatalytic Synthesis of 1,3-Mercaptoalkanols3 Photo-Biocatalytic Synthesis of 1,3-Mercaptoalkanols4 Photo-Biocatalysed Cascade Reactions5 Conclusions

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Rajakumara, Eerappa, Dubey Saniya, Priyanka Bajaj, Rajanna Rajeshwari, Jyotsnendu Giri, and Mehdi D. Davari. "Hijacking Chemical Reactions of P450 Enzymes for Altered Chemical Reactions and Asymmetric Synthesis." International Journal of Molecular Sciences 24, no. 1 (December 22, 2022): 214. http://dx.doi.org/10.3390/ijms24010214.

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Cytochrome P450s are heme-containing enzymes capable of the oxidative transformation of a wide range of organic substrates. A protein scaffold that coordinates the heme iron, and the catalytic pocket residues, together, determine the reaction selectivity and regio- and stereo-selectivity of the P450 enzymes. Different substrates also affect the properties of P450s by binding to its catalytic pocket. Modulating the redox potential of the heme by substituting iron-coordinating residues changes the chemical reaction, the type of cofactor requirement, and the stereoselectivity of P450s. Around thousands of P450s are experimentally characterized, therefore, a mechanistic understanding of the factors affecting their catalysis is increasingly vital in the age of synthetic biology and biotechnology. Engineering P450s can enable them to catalyze a variety of chemical reactions viz. oxygenation, peroxygenation, cyclopropanation, epoxidation, nitration, etc., to synthesize high-value chiral organic molecules with exceptionally high stereo- and regioselectivity and catalytic efficiency. This review will focus on recent studies of the mechanistic understandings of the modulation of heme redox potential in the engineered P450 variants, and the effect of small decoy molecules, dual function small molecules, and substrate mimetics on the type of chemical reaction and the catalytic cycle of the P450 enzymes.

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Langer, Peter, Silvio Parpart, Zorayr Mardiyan, Peter Ehlers, Andranik Petrosyan, Anna Mkrtchyan, and Ashot Saghyan. "Synthesis of Optically Pure (S,E)-2-Amino-5-arylpent-4-enoic Acids by Heck Reactions of Nickel Complexes." Synlett 29, no. 06 (January 15, 2018): 793–98. http://dx.doi.org/10.1055/s-0037-1609094.

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Starting from commercially available building blocks a variety of enantiomerically pure (S)-2-amino-4-enoic acids has been synthesized by the Heck reaction using Ni-(S)-BPB {Nickel-N-[(S)-benzylprolyl]aminobenzophenone} as a chiral auxiliary. The reactions proceeded in very good yields and with high E-selectivity.

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42

Song, Jinliang, Binbin Zhang, Suxiang Wu, Qian Wang, Honglei Fan, Zhaofu Zhang, and Buxing Han. "Synthesis of unsymmetrical organic carbonates catalyzed by a sulfonic acid-functionalized zirconium phosphonate." Pure and Applied Chemistry 84, no. 3 (September 30, 2011): 675–84. http://dx.doi.org/10.1351/pac-con-11-06-04.

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Synthesis of unsymmetrical organic carbonates by transesterification of various alcohols with diethyl carbonate (DEC) is an interesting topic in green chemistry. In this work, we synthesized a kind of zirconium phosphonate functionalized with pendent N-SO3H group by the reaction of ZrOCl2·8H2O with N,N-bis(phosphonomethyl)-sulfamic acid, which was formed from sulfamic acid through a Mannich-type reaction. The functionalized zirconium phosphonate was characterized by Fourier transform/infrared (FT/IR), N2 adsorption and desorption, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD) techniques, and was used as the heterogeneous catalyst for the synthesis of unsymmetrical organic carbonates by transesterification of various alcohols with DEC. It was demonstrated that the catalyst is very active and selective for the reactions, and very high yields of the desired products could be obtained. In addition, the catalyst could be easily recovered and the decrease in catalytic activity and selectivity was minor after three-fold usage. The mechanism for the transesterification reactions is discussed.

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Calascibetta, Adiel Mauro, Sara Mattiello, Alessandro Sanzone, Irene Facchinetti, Mauro Sassi, and Luca Beverina. "Sustainable Access to π-Conjugated Molecular Materials via Direct (Hetero)Arylation Reactions in Water and under Air." Molecules 25, no. 16 (August 14, 2020): 3717. http://dx.doi.org/10.3390/molecules25163717.

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Direct (hetero)arylation (DHA) is playing a key role in improving the efficiency and atom economy of C–C cross coupling reactions, so has impacts in pharmaceutical and materials chemistry. Current research focuses on further improving the generality, efficiency and selectivity of the method through careful tuning of the reaction conditions and the catalytic system. Comparatively fewer studies are dedicated to the replacement of the high-boiling-point organic solvents dominating the field and affecting the overall sustainability of the method. We show herein that the use of a 9:1 v/v emulsion of an aqueous Kolliphor 2 wt% solution while having toluene as the reaction medium enables the preparation of relevant examples of thiophene-containing π-conjugated building blocks in high yield and purity.

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Wei, Yin, Xu-Bo Hu, Kai Chen, and Min Shi. "Mechanistic studies for dirhodium-catalyzed ring expansion reactions." Organic Chemistry Frontiers 4, no. 6 (2017): 986–94. http://dx.doi.org/10.1039/c6qo00713a.

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Nguyen, Trang, Hung Mac, and Phong Pham. "Preparation of Key Intermediates for the Syntheses of Coenzyme Q10 and Derivatives by Cross-Metathesis Reactions." Molecules 25, no. 3 (January 21, 2020): 448. http://dx.doi.org/10.3390/molecules25030448.

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An alternative catalytic strategy for the preparation of benzylmethacrylate esters, key intermediates in the synthesis of coenzyme Q10 and derivatives, was reported. This strategy avoided undesirable stoichiometric reduction/oxidation processes by utilizing the catalytic formation of allylarenes and then cross-metathesis to selectively form E-benzylmethacrylate esters with good yields (58–64%) and complete E-selectivity. The ester intermediates were reduced to common key benzylallylic alcohols (90–92% yield), which were subsequently used in the formal syntheses of coenzyme Q10 and one derivative.

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Arnodo, Davide, Elia Maffeis, Francesco Marra, Stefano Nejrotti, and Cristina Prandi. "Combination of Enzymes and Deep Eutectic Solvents as Powerful Toolbox for Organic Synthesis." Molecules 28, no. 2 (January 5, 2023): 516. http://dx.doi.org/10.3390/molecules28020516.

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During the last decade, a wide spectrum of applications and advantages in the use of deep eutectic solvents for promoting organic reactions has been well established among the scientific community. Among these synthetic methodologies, in recent years, various examples of biocatalyzed processes have been reported, making use of eutectic mixtures as reaction media, as an improvement in terms of selectivity and sustainability. This review aims to show the newly reported protocols in the field, subdivided by reaction class as a ‘toolbox’ guide for organic synthesis.

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Wang, Yayue, Chang Zhang, Haoxing Wu, and Ping Feng. "Activation and Delivery of Tetrazine-Responsive Bioorthogonal Prodrugs." Molecules 25, no. 23 (November 30, 2020): 5640. http://dx.doi.org/10.3390/molecules25235640.

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Prodrugs, which remain inert until they are activated under appropriate conditions at the target site, have emerged as an attractive alternative to drugs that lack selectivity and show off-target effects. Prodrugs have traditionally been activated by enzymes, pH or other trigger factors associated with the disease. In recent years, bioorthogonal chemistry has allowed the creation of prodrugs that can be chemically activated with spatio-temporal precision. In particular, tetrazine-responsive bioorthogonal reactions can rapidly activate prodrugs with excellent biocompatibility. This review summarized the recent development of tetrazine bioorthogonal cleavage reaction and great promise for prodrug systems.

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Ward, Dale E., Yadong Liu, and Chung K. Rhee. "Asymmetric synthesis using reactions with modest group selectivity." Canadian Journal of Chemistry 72, no. 6 (June 1, 1994): 1429–46. http://dx.doi.org/10.1139/v94-180.

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The isomeric purity of products from certain group-selective reactions can be significantly amplified when reactions can occur sequentially. The theoretical basis for a strategy that exploits reactions with modest enantiotopic group selectivity for asymmetric synthesis is described. The relationships between conversion, yield, and isomeric purity for such a process are calculated using a simple kinetic model. A simple method for selecting candidate group-selective reactions from known face-selective reactions is presented. Application of the strategy is illustrated with the reduction of D-glucose and D-galactose derived dialdehydes with B-isopinocampheyl-9-borabicyclo[3.3.1]nonane (Alpine-Borane®).

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Chen, Jian, Mengjing Zhu, Fuwei Xiang, Junfeng Li, Hongjun Yang, and Zhipeng Mao. "Research Progress on Microreactor Technology in Oxidation Reactions." Current Organic Chemistry 25, no. 10 (June 1, 2021): 1235–45. http://dx.doi.org/10.2174/1385272825666210319092545.

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In recent years, the development of the chemical industry has been moving in a green, safe and efficient direction. Oxidation reactions are one of the most important types of reactions and have key applications in food, medicine, cosmetics, and petrochemicals. However, the occurrence of the oxidation reaction is accompanied by a strong exothermic phenomenon, and improper control can easily lead to safety problems and even explosions. The realization of an environmentally friendly oxidation reaction is a key industrial milestone. The unique structural characteristics of microreactors result in good mass and heat transfer performance, precise control of the reaction temperature, reduced risk of explosion, improved safety production and selectivity of products. These unique advantages of the microreactor determine its significant application value in oxidation reactions. In this paper, the research progress of several typical oxidation reactions, including alkane oxidation, alcohol oxidation, aldosterone oxidation, aromatics oxidation and olefin oxidation combined with microreactors, is reviewed systematically.

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Bur, Scott K., and Stephen F. Martin. "Vinylogous Mannich reactions: selectivity and synthetic utility." Tetrahedron 57, no. 16 (April 2001): 3221–42. http://dx.doi.org/10.1016/s0040-4020(01)00035-7.

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Journal articles on the topic 'Organic Chemistry Reactions - Selectivity'

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