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Dieter Vogt - One of the best experts on this subject based on the ideXlab platform.
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enantioselective nickel catalyzed Hydrocyanation using chiral phosphine phosphite ligands recent improvements and insights
Advanced Synthesis & Catalysis, 2015Co-Authors: Anna Falk, Dieter Vogt, Alberto Cavalieri, Gary S Nichol, Hansgunther SchmalzAbstract:The asymmetric Hydrocyanation of vinylarenes was investigated using hydrogen cyanide (HCN) in the presence of 5 mol% of a catalyst prepared from a phenol-derived chiral phosphine-phosphite ligand and bis(cyclooctadiene)nickel [Ni(cod)2]. The reactions were performed in tetrahydrofuran (THF) at room temperature to give exclusively the branched nitriles with superior enantioselectivities of 88–99% ee for vinylarenes and 74–94% ee for vinylheteroarenes, respectively. Using styrene as a model substrate it was shown that the catalyst loading could be decreased to 0.42 mol% without any loss of selectivity (88% ee). The structure of the pre-catalyst, i.e., a tetrahedral Ni(0)(P,P-chelate)(cod) complex, was proven by X-ray and NMR analysis. Additional insight into the reaction course was gained by monitoring the Hydrocyanation of styrene-d8 by means of 2D NMR spectroscopy.
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ligand development in the ni catalyzed Hydrocyanation of alkenes
Chemical Communications, 2010Co-Authors: Laura Bini, Christian Müller, Dieter VogtAbstract:The addition of HCN to alkenes is a very useful reaction for the synthesis of functional organic substrates. Industrially the nickel-catalyzed Hydrocyanation has gained considerable importance mainly because of the production of adiponitrile in the DuPont process. In this process the Hydrocyanation of butadiene is carried out using aryl phosphite-modified nickel catalyst. Since the performance of organo-transition metal complexes is largely determined by the ligand environment of the metal, fundamental understanding and ligand development is of pivotal importance for any progress. This feature article gives an account of the development and application of different mono- and bidentate phosphorus-based ligands in the Ni-catalyzed Hydrocyanation reaction of alkenes. Special attention will be paid to the development of insight and understanding of the ligand structural and electronic properties towards the improvement of the catalyst performance in terms of stability, activity, and selectivity.
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Mechanistic Studies on Hydrocyanation Reactions
Chemcatchem, 2010Co-Authors: Laura Bini, Christian Müller, Dieter VogtAbstract:This Review summarizes the state of the art in transition metal-catalyzed alkene Hydrocyanation with special emphasis on mechanistic studies. Due to its importance for the DuPont adiponitrile process, most of the literature deals with the nickel-catalyzed Hydrocyanation. Ligand electronic and steric effects, as well as the bite angle of chelating ligands, play a dominant role for the catalyst performance. The ligand properties have a major effect on the catalyst stability and on the rate limiting step - the reductive elimination of the products. The DuPont process, comprises three separate steps: a) the Hydrocyanation of 1,3-butadiene and other conjugated dienes, b) the isomerization of 2-methyl-3-butenenitrile to 3-pentenenitrile, and c) the Hydrocyanation of 3-pentenenitrile and other monoalkenes. Existing knowledge of these steps is summarized and elucidated. For the latter reactions, Lewis acid cocatalysts are imperative, and their influence on the regioselectivity and the catalyst performance will be discussed. Asymmetric alkene Hydrocyanation has attracted considerable interest recently and is covered from a mechanistic viewpoint. Finally, a short account is given on other metals applied in alkene Hydrocyanation. More detailed mechanistic understanding is still required for the improvement of catalyst performance and to develop this reaction to its full potential in organic synthesis.
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Lewis Acid Controlled Regioselectivity in Styrene Hydrocyanation
Chemistry (Weinheim an der Bergstrasse Germany), 2009Co-Authors: Laura Bini, Evgeny A. Pidko, Christian Müller, Rutger A. Van Santen, Dieter VogtAbstract:According to present knowledge, the Ni-catalyzed Hydrocyanation of styrene leads predominantly to the branched product 2-phenylpropionitrile (98%). We observed a dramatic inversion of the regioselectivity upon addition of a Lewis acid. Up to 83 % of the linear product 3-phenylpropionitrile was obtained by applying phosphite Iigands in the presence of AlCl3. The mechanism of the Ni-catalyzed reaction and the influence of additional Lewis acids have been investigated by means of deuterium labeling experiments, NMR studies, and DFT calculations. Furthermore, the behavior of different Lewis acids, such as CuCN, could be rationalized and predicted by DFT calculations. © 2009 Wiley-VCH Verlag GmbH & Cu. KGaA.
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highly selective Hydrocyanation of butadiene toward 3 pentenenitrile
Journal of the American Chemical Society, 2007Co-Authors: Laura Bini, Christian Müller, Jos Wilting, Lars Von Chrzanowski, And Anthony L Spek, Dieter VogtAbstract:A triptycene-based diphosphine ligand was synthesized in good yield following a new route. The corresponding Pt(II)- and Ni(0)-complexes were characterized. In butadiene Hydrocyanation the tript-PPh2Ni(cod) catalyst leads to exceptionally high selectivities for the linear product 3-pentenenitrile, combining high activity for both Hydrocyanation and isomerization. This one-step procedure could be the key toward process intensification.
Armido Studer - One of the best experts on this subject based on the ideXlab platform.
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nickel catalyzed markovnikov transfer Hydrocyanation in the absence of lewis acid
Organic Letters, 2020Co-Authors: Nils L Frye, Anup Bhunia, Armido StuderAbstract:Hydrocyanation in the absence of toxic HCN gas is highly desirable. Addressing that challenge, transition-metal-catalyzed transfer Hydrocyanation using safe HCN precursors has been developed, but t...
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cooperative palladium lewis acid catalyzed transfer Hydrocyanation of alkenes and alkynes using 1 methylcyclohexa 2 5 diene 1 carbonitrile
Journal of the American Chemical Society, 2018Co-Authors: Anup Bhunia, Klaus Bergander, Armido StuderAbstract:Catalytic transfer Hydrocyanation represents a clean and safe alternative to Hydrocyanation processes using toxic HCN gas. Such reactions provide access to pharmaceutically important nitrile derivatives starting with alkenes and alkynes. Herein, an efficient and practical cooperative palladium/Lewis acid-catalyzed transfer Hydrocyanation of alkenes and alkynes is presented using 1-methylcyclohexa-2,5-diene-1-carbonitrile as a benign and readily available HCN source. A large set of nitrile derivatives (>50 examples) are prepared from both aliphatic and aromatic alkenes with good to excellent anti-Markovnikov selectivity. A range of aliphatic alkenes engage in selective Hydrocyanation to provide the corresponding nitriles. The introduced method is useful for chain walking Hydrocyanation of internal alkenes to afford terminal nitriles in good regioselectivities. This protocol is also applicable to late-stage modification of bioactive molecules.
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Cooperative Palladium/Lewis Acid-Catalyzed Transfer Hydrocyanation of Alkenes and Alkynes Using 1‑Methylcyclohexa-2,5-diene-1-carbonitrile
2018Co-Authors: Anup Bhunia, Klaus Bergander, Armido StuderAbstract:Catalytic transfer Hydrocyanation represents a clean and safe alternative to Hydrocyanation processes using toxic HCN gas. Such reactions provide access to pharmaceutically important nitrile derivatives starting with alkenes and alkynes. Herein, an efficient and practical cooperative palladium/Lewis acid-catalyzed transfer Hydrocyanation of alkenes and alkynes is presented using 1-methylcyclohexa-2,5-diene-1-carbonitrile as a benign and readily available HCN source. A large set of nitrile derivatives (>50 examples) are prepared from both aliphatic and aromatic alkenes with good to excellent anti-Markovnikov selectivity. A range of aliphatic alkenes engage in selective Hydrocyanation to provide the corresponding nitriles. The introduced method is useful for chain walking Hydrocyanation of internal alkenes to afford terminal nitriles in good regioselectivities. This protocol is also applicable to late-stage modification of bioactive molecules
Xianjie Fang - One of the best experts on this subject based on the ideXlab platform.
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nickel catalyzed migratory Hydrocyanation of internal alkenes unexpected diastereomeric ligand controlled regiodivergence
Angewandte Chemie, 2021Co-Authors: Jihui Gao, Guijuan Cheng, Mingdong Jiao, Xianjie FangAbstract:A regiodivergent nickel-catalyzed Hydrocyanation of a broad range of internal alkenes involving a chain-walking process is reported. When appropriate diastereomeric biaryl diphosphite ligands are applied, the same starting materials can be converted to either linear or branched nitriles with good yields and high regioselectivities. DFT calculations suggested that the catalyst architecture determines the regioselectivity by modulating electronic and steric interactions. In addition, moderate enantioselectivities were observed when branched nitriles were produced.
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enantioselective nickel catalyzed migratory Hydrocyanation of nonconjugated dienes
Angewandte Chemie, 2020Co-Authors: Shanmugam Rajasekar, Xianjie FangAbstract:Metal-catalyzed chain-walking reactions have recently emerged as a powerful strategy to functionalize remote positions in organic molecules. However, a chain-walking protocol for nonconjugated dienes remains scarcely reported, and developments are currently ongoing. In this Communication, a nickel-catalyzed asymmetric Hydrocyanation of nonconjugated dienes involving a chain-walking process is demonstrated. The reaction exhibits excellent regio- and chemoselectivity, and a wide range of substrates were tolerated, delivering the products in high yields and enantioselectivities. Deuterium-labeling experiments support the chain-walking process, which involves an iterative β-H elimination and reinsertion processes. Gram-scale synthesis, regioconvergent experiments, and downstream transformations gave further insights into the high potential of this transformation.
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highly regio and stereoselective ni catalyzed Hydrocyanation of 1 3 enynes
Chemistry: A European Journal, 2020Co-Authors: Feilong Sun, Guijuan Cheng, Xianjie FangAbstract:A highly regio- and stereoselective Hydrocyanation of 1,3-enynes was implemented by nickel/diphosphine catalysts. A wide range of highly regio- and stereoselective alkenyl nitriles were efficiently prepared. In this transformation, both the tethered alkene and the ligand play key roles in the reactivity and selectivity. The origin of regioselectivity was understood preliminarily by DFT studies.
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access to 1 3 dinitriles by enantioselective auto tandem catalysis merging allylic cyanation with asymmetric Hydrocyanation
Angewandte Chemie, 2020Co-Authors: Jinguo Long, Jihui Gao, Xianjie FangAbstract:Enantioselective auto-tandem catalysis represents a challenging yet highlight attractive topic in the field of asymmetric catalysis. In this context, we describe a dual catalytic cycle that merges allylic cyanation and asymmetric Hydrocyanation. The one-pot conversion of a broad array of allylic alcohols into their corresponding 1,3-dinitriles proceeds in good yield with high enantioselectivity. The products are densely functionalized and can be easily transformed to chiral diamines, dinitriles, diesters, and piperidines. Mechanistic studies clearly support a novel sequential cyanation/Hydrocyanation pathway.
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highly enantioselective nickel catalyzed Hydrocyanation of disubstituted methylenecyclopropanes enabled by taddol based diphosphite ligands
Organic Letters, 2020Co-Authors: Xianjie FangAbstract:A vast range of novel TADDOL-based diphosphite ligands were first synthesized and applied in the nickel-catalyzed asymmetric Hydrocyanation of disubstituted methylenecyclopropanes. By employing these new catalysts, the conversion of diverse methylenecyclopropanes into their corresponding allylic nitriles was first enabled, in good yield with excellent enantioselectivities.
Takeshi Ohkuma - One of the best experts on this subject based on the ideXlab platform.
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catalytic asymmetric cyanation reactions
ChemInform, 2016Co-Authors: Nobuhito Kurono, Takeshi OhkumaAbstract:Catalytic asymmetric cyanations of prochiral unsaturated compounds affording the corresponding nitrile products in high enantiomeric excess (≥90% in general) are summarized in this review. The nucleophilic cyanide addition onto aldehydes, ketones, and imines is promoted by chiral metal complexes and organocatalysts. Recent progress in asymmetric conjugate cyanation of α,β-unsaturated carbonyl compounds is also discussed. The asymmetric cyanation of unactivated alkenes is catalyzed by chiral transition-metal complexes. Current topics of intramolecular carbocyanation and aminocyanation in addition to the traditional Hydrocyanation are reviewed.
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asymmetric conjugate Hydrocyanation of α β unsaturated n acylpyrroles with the ru phgly 2 binap ch3oli catalyst system
Organic Letters, 2014Co-Authors: Yusuke Sakaguchi, Nobuhito Kurono, Kohei Yamauchi, Takeshi OhkumaAbstract:Asymmetric conjugate Hydrocyanation of α,β-unsaturated carboxylic acid derivatives catalyzed by a Ru[(S)-phgly]2[(S)-binap]–CH3OLi system was examined. The N-acylpyrrole gave the best result in terms of reactivity and enantioselectivity. A series of substrates with alkyl or heterosubstituted alkyl groups at the β-position reacted with a substrate-to-catalyst molar ratio of 200–2000 to afford the β-cyano products in the range of 88%–>99% ee. The mode of enantioselection in the Hydrocyanation was proposed.
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Asymmetric Conjugate Hydrocyanation of α,β-Unsaturated N‑Acylpyrroles with the Ru(phgly)2(binap)–CH3OLi Catalyst System
2014Co-Authors: Yusuke Sakaguchi, Nobuhito Kurono, Kohei Yamauchi, Takeshi OhkumaAbstract:Asymmetric conjugate Hydrocyanation of α,β-unsaturated carboxylic acid derivatives catalyzed by a Ru[(S)-phgly]2[(S)-binap]–CH3OLi system was examined. The N-acylpyrrole gave the best result in terms of reactivity and enantioselectivity. A series of substrates with alkyl or heterosubstituted alkyl groups at the β-position reacted with a substrate-to-catalyst molar ratio of 200–2000 to afford the β-cyano products in the range of 88%–>99% ee. The mode of enantioselection in the Hydrocyanation was proposed
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enantioselective Hydrocyanation of n protected aldimines
ChemInform, 2012Co-Authors: Masato Uemura, Nobuhito Kurono, Takeshi OhkumaAbstract:Enantioselective Hydrocyanation of N-benzyloxycarbonyl aldimines catalyzed by a Ru[(S)-phgly]2[(S)-binap]/C6H5OLi system or a bimetallic complex [Li{Ru[(S)-phgly]2[(S)-binap]}]Cl affords the amino nitriles in 92–99% ee. The reaction is carried out in tert-C4H9OCH3 with a substrate-to-catalyst molar ratio in the range of 500–5000 at −20 to 0 °C. Primary, secondary, and tertiary alkyl imines as well as the aryl and heteroaryl substrates are smoothly cyanated to produce the desired products in high yield.
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enantioselective Hydrocyanation of aldehydes catalyzed by li ru phgly 2 binap x x cl br
ChemInform, 2011Co-Authors: Nobuhito Kurono, Tatsuya Yoshikawa, Mikio Yamasaki, Takeshi OhkumaAbstract:The Ru complexes (I) are found to be highly efficient catalysts for the asymmetric Hydrocyanation of aromatic, α,β-unsaturated, and tert-alkyl aldehydes.
Li Dang - One of the best experts on this subject based on the ideXlab platform.
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transfer Hydrocyanation by nickel 0 lewis acid cooperative catalysis mechanism investigation and computational prediction of shuttle catalysts
Organometallics, 2017Co-Authors: Ti-long Yang, Li DangAbstract:A theoretical investigation on transfer Hydrocyanation of simple olefins catalyzed by shuttle catalysts is presented in this work, which uncovers the reaction mechanism together with the important role of the Lewis acid. The calculated results show that Ni(0)/LA (Lewis acid)-catalyzed transfer Hydrocyanation consists of five key steps: oxidative addition of the nitrile, β-H elimination, ligand exchange, alkene insertion, and reductive elimination. The computational results reveal that the effect of the Lewis acid is mainly reflected in the interaction with the N atom of the nitrile group, which weakens the C(sp3)–C(sp) σ bond, thus lowering the barrier of the oxidative addition step, which is the rate-determining step of the catalyzed reaction. These results are consistent with the experimental observations. Furthermore, our calculation results with several newly designed ligands show that the introduction of an electron-donating group to the phosphine ligand promotes transfer Hydrocyanation, while an ele...
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Transfer Hydrocyanation by Nickel(0)/Lewis Acid Cooperative Catalysis, Mechanism Investigation, and Computational Prediction of Shuttle Catalysts
2017Co-Authors: Ti-long Yang, Li DangAbstract:A theoretical investigation on transfer Hydrocyanation of simple olefins catalyzed by shuttle catalysts is presented in this work, which uncovers the reaction mechanism together with the important role of the Lewis acid. The calculated results show that Ni(0)/LA (Lewis acid)-catalyzed transfer Hydrocyanation consists of five key steps: oxidative addition of the nitrile, β-H elimination, ligand exchange, alkene insertion, and reductive elimination. The computational results reveal that the effect of the Lewis acid is mainly reflected in the interaction with the N atom of the nitrile group, which weakens the C(sp3)–C(sp) σ bond, thus lowering the barrier of the oxidative addition step, which is the rate-determining step of the catalyzed reaction. These results are consistent with the experimental observations. Furthermore, our calculation results with several newly designed ligands show that the introduction of an electron-donating group to the phosphine ligand promotes transfer Hydrocyanation, while an electron-withdrawing group blocks this reaction. The present work will provide great support for the understanding of transfer Hydrocyanation and give a valuable guide for the further design of transition-metal/Lewis acid cooperative shuttle catalysts