Reaction of diazocyclopropane with steroidal 16-bromo-17-ketones

Abstract

The reaction of diazocyclopropane with both 16α- and 16β-bromo-3β-acetoxy-5β-androstane-11,17-dione has been found to give a mixture of the four possible 16-bromo-17-spiro-oxirans (4a), (4b), (5a), and (5b), of which (17R)-3β-acetoxy-16α-bromodispiro[5β-androstane-17,2′-oxiran-3′,1″-cyclopropane]-11-one (5a) was found to be the major isomer. Rearrangements of these spiro-oxirans by boron trifluoride to give 17-spirocyclobutanones are described. Mechanisms of both reactions are discussed.