Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The stereochemistry of epoxidation, Simmons-Smith methylenation and addition of bromine and hypobromous acid to 5,6-unsaturated A-nor-3,5-secosteroids was studied. The additions proceed from both sides of the molecule and, the β-oriented positively charged intermediate is regularly cleaved under participation by the substituent at C₍₃₎ to the corresponding oxa derivative II or to the lactones VI and XI. Cleavage of the cyclopropano derivative XVI with thallium(III) acetate was accompanied by Westphalen rearrangement and lead to the 5-membered lactone XXI. The structures of the products were established by spectral and chemical means and the mechanisms of reactions observed are discussed.