Enantioselective Synthesis of<i>N</i>,<i>S</i>‐Acetals by an Oxidative Pummerer‐Type Transformation using Phase‐Transfer Catalysis

Biswas, Souvagya; Kubota, Koji; Orlandi, Manuel; Turberg, Mathias; Miles, Dillon H.; Sigman, Matthew S.; Toste, F. Dean

doi:10.1002/ange.201711277

Cited by 12 publications

(5 citation statements)

References 72 publications

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“…Recently, Toste et al developed the first catalytic, asymmetric Pummerer-type reaction using a chiral-anion phase-transfer catalyst 77 (Scheme 17c). 52 Therein, the insoluble oxidant 78 is brought into solution by anion exchange with catalytic amounts of 77. This highly electrophilic species can achieve hydride abstraction adjacent to sulfur, triggering an intramolecular cyclization to form N,S-acetal products (79).…”

Section: Sulfoxides 21 Pummerer Reactionsmentioning

confidence: 99%

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

et al. 2019

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Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.

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Section: Sulfoxides 21 Pummerer Reactionsmentioning

confidence: 99%

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

et al. 2019

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“…Accordingly, it has been proposed that the interaction between the iminium intermediate and the catalyst can only be ionic. 58 59 Investigations on epoxidation, 19 cross-dehydrogenative coupling, 60,61 Pummerer 62 and ring-opening 63 reactions involving diverse cationic substrates have also concluded that a similar mechanism could be in operation.…”

Section: Phosphate-catalyzed Transfer Hydrogenationmentioning

confidence: 99%

“…88 89 90 In 2018, Sigman and Toste described an enantioselective Pummerer-type transformation that generates cyclic N , S -acetals (Scheme 4 ). 62 These reactions were proposed to proceed through thionium intermediates and operate with lower enantioselectivities than products obtained in comparable reactions involving iminium intermediates. DFT calculations suggested that the catalyst interacts only with the proton of the nucleophile, in agreement with the reaction models available at that time.…”

Section: Chiral Phosphates and Thionium Intermediatesmentioning

confidence: 99%

Reaction Mechanisms for Chiral-Phosphate-Catalyzed Transformations Involving Cationic Intermediates and Protic Nucleophiles

Zhai¹,

Reid²

2022

Synlett

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Recent strategies for enantioinduction often focus on employing a chiral catalyst to noncovalently interact with the substrate. By restricting the number of low energy diastereomeric transition states the reacting components can adopt, stereoselectivity can be achieved. Many of these noncovalent interactions include a significant dispersive component and these types of contacts have historically been difficult to model accurately. Modern computational methods have been designed to overcome such limitations. Using our computational work in chiral phosphate catalysis, we discuss the reasons for enantioselectivity in diverse reaction space.

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“…In the 2017, Sigman and Toste developed and studied an enantioselective Pummerer reaction based on a chiral anion phase transfer process [49]. In this reaction, a benzylic thioether 32 is oxidized in situ in by an oxammonium salt 33 in the presence of chiral phosphate 1o.…”

Section: Enantioselective Pummerer Reactionmentioning

confidence: 99%

Basic principles of substrate activation through non-covalent bond interactions

Orlandi

2020

Physical Sciences Reviews

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AbstractIn the last twenty years, chiral Brønsted acid and chiral counteranion catalysis have emerged as a fundamental area of organocatalysis. The development of chiral acidic catalysts has allowed extending many known Brønsted catalyzed reactions to the stereoselective domain. Moreover, the controlled conditions under which these catalysts can be used, allowed accessing reactivity of increasing complexity with extraordinary selectivity levels. However, compared to the explosion of this branch of organocatalysis in an applicative direction, only little has been done to understand and rationalize the observed reaction outcomes. This is due, in part, to the complex nature of the weak interactions (H-bonds, electrostatic, and dispersion interactions) governing this class of reactions. Here we review relevant mechanistic analyses from both chiral Brønsted acid and chiral counteranion directed catalysis. Both experimental and computational work is included that aimed at unveiling the nature of the interactions governing the a number of reactions. These include the: enantioselective reduction of ketoimines with Hantzsch esters; ring opening reactions of epoxides, oxetanes, aziridinium, and sulfonium ions; stereoselective fluorination of allylic alcohols; oxidative aminations of benzylic thioethers (enantioselective Pummerer reaction). These case studies are analyzed and discussed in order to highlight key features and similarities across the different catalytic systems.

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Enantioselective Synthesis ofN,S‐Acetals by an Oxidative Pummerer‐Type Transformation using Phase‐Transfer Catalysis

Cited by 12 publications

References 72 publications

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

Reaction Mechanisms for Chiral-Phosphate-Catalyzed Transformations Involving Cationic Intermediates and Protic Nucleophiles

Basic principles of substrate activation through non-covalent bond interactions

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