Stereochemistry of epoxidation of cholest-5-en-3-one and of the base-catalysed rearrangement of the derived epoxides

Abstract

The epoxidation of cholest-5-en-3-one by m-chloroperbenzoic acid in deuteriochloroform and in benzene has been investigated by ¹H n.m.r. spectroscopy. The product mixtures contain 3,4-secocholest-5-eno-3,4-lactone and the α-epoxide, both recognised by previous workers; the β-epoxide accompanies them, the α : β ratio being ca. 2 : 1 in both solvents. Both α- and β-epoxides undergo smooth rearrangement when treated with pyridine in deuteriochloroform, and give the expected 6-hydroxycholest-4-en-3-one. By this treatment the mixed products of epoxidation of 4β-deuteriocholest-5-en-3-one lose exclusively (within experimental error) the 4α-hydrogen atom. The epoxidation of some 3α- and 3β-substituted cholest-5-enes under the same conditions was also carried out to monitor our experimental procedures.