Betaine Decomposition Studies of Arsonium Ylides Leading to Lactonyl and Lactothionyl Olefination

Abstract

The synthetic potential of the Wittig reaction has reached the maximum as a most versatile tool for carbonyl olefination^1–4, but our interest in this field arises from a wish to extend this area to some other types of olefination reactions.^5,6 Until now it has been well established that olefination, either via phosphonium ylides or arsonium ylides, proceeds via stepwise formation of a betaine type compound and a four membered intermediate. It is the decomposition pattern of the betaines which is mainly responsible for the nature of product formation. We have recently carried out a thorough investigation of the arsonium betaines of carbonyls and exocyclic thiocarbonyls.^7,8 However, the decomposition pattern of betaines formed by the nucleophilic attack of these ylides on α-lactonyl and α-lactothionyl systems still remains uninvestigated.