The bromination of some cholest-5-en-7-ones

Abstract

Bromination (Br₂–HBr–HOAc) of cholest-5-en-7-one (1) gives 5,6α-dibromo-5β-cholestan-7-one (4), whereas 3β-acetoxycholest-5-en-7-one (2) gives the 5α,6β-dibromo-product (5). Addition products (6) and (7) of both types are formed from the 3β-chloro-derivative (3). Products isolated from the reaction of pyridine with the 5,6 dibromides (4)–(6) and 4,5,6-tribromide (7) include a 5-en-7-one (1)–(3), a 6-bromo-5-en-7-one (8), a 6-bromo-3,5-dien-7-one (9), a 3,5-dien-7-one (10), and a 4,6-dibromo-3,5-dien-7-one (11). The structures have been established on the basis of elemental analysis and spectral properties.