19-Hydroxy-steroids. Part 7. Boron trifluoride-catalysed reactions of 19-hydroxy- and 19-acetoxy-5,6-epoxy-steroids

Abstract

The effects of strong electron-withdrawing substituents at C-19 upon the boron trifluoride-catalysed reactions of 5,6-epoxy-steroids were examined. 3β-Acetoxy-5,6β-epoxy-5β-cholestan-19-ol (4) and 3β-acetoxy-5,6β-epoxy-19-hydroxy-5β-androstan-17-one (2) reacted with boron trifluoride gas in benzene with the loss of the C-10 groups as formaldehyde and subsequent dehydration to give the 1(10),5-dienes (16) and (17), respectively. 3β,19-Diacetoxy-5,6β-epoxy-5β-cholestane (5) and 3β,19-diacetoxy-5,6β-epoxy-5β-androstan-17-one (3) gave as the only rearrangement product the B-nor-5β-formyl-steroids (26) and (25). 3β-Acetoxy-5,6α-epoxy-5α-cholestan-19-ol (12) and its 19-acetate derivative (13) gave products arising from the participation of the 19-function in the epoxide opening.