Transformation of cyclic α-phenylthio aldehydes by stereoselective aldol reactions and phenylthio migration into spirocyclic lactones and ethers, and E-allylic alcohols with 1,4-related chiral centres

Abstract

syn- and anti-Selective aldol reactions between enolates of propionate esters and three α-phenylthio cycloalkanecarbaldehydes give single diastereoisomers of phenylthio alcohols which rearrange in acid with 5-hydroxy or 5-CO₂H participation to give spirocyclic ethers or lactones. In the absence of internal nucleophiles, allylic sulphides are formed which are used to make allylic alcohols with an E double bond exo to the ring and two stereochemically defined 1,4-related chiral centres.