Asymmetric deprotonation Subject

A number of subjects related to protonation or deprotonation (such as stereoselectivity, hydrolysis mechanisms or asymmetric induction) will be avoided, since they are dealt with in other chapters of this volume. 

Condensation with carbonyl compounds. Formation of epoxides from aldehydes by reaction with sulfonium ylides is subject to asymmetric induction. The latter species have been generated from 91, 92, and 93, and also those derived from monoterpenes, e.g., 94 " and 95.- Of course the ylides can be obtained in situ by deprotonation of sulfonium salts or copper-catalyzed decomposition of diazoalkanes (with the carbenoids trapped by the sulfides). 

The first example of asymmetric thio-Claisen rearrangement based on axial chirality has been described by our group and involves atropisomeric thioanilides bearing an ortbo-tert-butyl group [132]. These axially chiral thioamides were subjected to LDA deprotonation followed by S-allylation with various allyl halides. 

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