Synthesis of steroidal azides. Part 1. Stereospecific vicinal azidohydroxylation of steroidal olefins

Abstract

A novel method for the direct conversion of steroidal olefins into vicinal azidohydrins has been discovered. Reaction of 20-oxopregn-5-en-3β-yl acetate (3) with chromium trioxide and sodium azide in glacial acetic acid is shown to give 6β-azido-20-oxopregnane-3β,5α-diol 3-acetate (4) as the major product, whereas 3,20-dioxopregna-4,6-dien-17α-yl acetate (8) leads to a mixture, containing 7α-azido-3,20-dioxopregn-4-ene-6β,17α-diol 17-acetate (12), together with smaller amounts of 6β,7α-diazido-3,20-dioxopregn-4-en-17α-yl acetate (10) and 7α-azido-3,6,20-trioxopregn-4-en-17α-yl acetate (11). Reaction mechanisms are proposed to interpret these results.