70991-79-6Relevant articles and documents
An Asymmetric SN2 Dynamic Kinetic Resolution
Rezayee, Nomaan M.,Enem?rke, Valdemar J.,Linde, Sif T.,Lamhauge, Johannes N.,Reyes-Rodríguez, Gabriel J.,J?rgensen, Karl Anker,Lu, Chenxi,Houk
supporting information, p. 7509 - 7520 (2021/05/26)
The SN2 reaction exhibits the classic Walden inversion, indicative of the stereospecific backside attack of the nucleophile on the stereogenic center. Observation of the inversion of the stereocenter provides evidence for an SN2-type displacement. However, this maxim is contingent on substitution proceeding on a discrete stereocenter. Here we report an SN2 reaction that leads to enantioenrichment of product despite starting from a racemic mixture of starting material. The enantioconvergent reaction proceeds through a dynamic Walden cycle, involving an equilibrating mixture of enantiomers, initiated by a chiral aminocatalyst and terminated by a stereoselective SN2 reaction at a tertiary carbon to provide a quaternary carbon stereocenter. A combination of computational, kinetic, and empirical studies elucidates the multifaceted role of the chiral organocatalyst to provide a model example of the Curtin-Hammett principle. These examples challenge the notion of enantioenriched products exclusively arising from predefined stereocenters when operating through an SN2 mechanism. Based on these principles, examples are included to highlight the generality of the mechanism. We anticipate the asymmetric SN2 dynamic kinetic resolution to be used for a variety of future reactions.
Pummerer Cyclization Revisited: Unraveling of Acyl Oxonium Ion and Vinyl Sulfide Pathways
Li, Xin,Carter, Rich G.
supporting information, p. 5541 - 5545 (2018/09/25)
Two viable pathways (vinyl sulfide and acyl oxonium ion) for the Pummerer cyclization have been unraveled that expand the reaction scope and capabilities. Use of Br?nsted-enhanced Lewis acidity was key to realization of the vinyl sulfide pathway, whereas selective complexation of the sulfur lone pair facilitated the unprecedented acyl oxonium ion pathway. Preliminary mechanistic investigations support these hypotheses. A range of substrates have been explored to understand the reaction parameters.
An air-stable cationic iridium hydride as a highly active and general catalyst for the isomerization of terminal epoxides
Humbert, Nicolas,Vyas, Devendra J.,Besnard, Céline,Mazet, Clément
supporting information, p. 10592 - 10595 (2014/10/15)
We describe the use of an air-stable iridium hydride catalyst for the isomerization of terminal epoxides into aldehydes with perfect regioselectivity. The system operates at low loadings of catalyst (0.5 mol%), is highly practical, scalable, and tolerates functional groups that would not be compatible with Lewis acids typically used in stoichiometric amounts. Evidence for a rare hydride mechanism are provided. This journal is the Partner Organisations 2014.
