REGIOSELECTIVE DEHYDRATION OF AXIAL AND EQUATORIAL TERTIARY ALCOHOLS WITH ALPHA-METHYL GROUP IN THE CYCLOHEXANE RING BY SWERN REAGENT

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