Regioselective dehydration of axial and equatorial tertiary alcohols with α-methyl group in the cyclohexane ring by Swern’s reagent

Abstract

Swern’s reagent (a complex of oxalyl chloride with DMSO) was shown to dehydrate tertiary alcohols containing an α-methyl group in the cyclohexane ring. Dehydration of equatorial alcohols affords mixtures of isomeric compounds where isomers with an exocyclic double bond dominate, whereas isomers with an endocyclic double bond prevail in the products of dehydration of axial tertiary alcohols. Thus, Swern’s reagent can serve as a chemical test to determine the configuration of tertiary alcohols containing an α-methyl group in cyclohexane ring. The composition of the products of dehydration of these alcohols with Swern’s reagent is similar to that obtained by their dehydration with POCl3 in pyridine.