Reactions of steroid A-ring lactones with Grignard reagents

Abstract

The addition of solutions of Grignard reagents to 4-oxacholesta-5,7-dien-3-one (4) yields the bridged ketones 3-alkyl-3-hydroxy-3(5 → 6βH)abeo-A-norcholest-7-en-5-ones (12) as well as ‘over-reacted’ products which are formed from the latter by reduction (as against Grignard addition) at the 5-carbonyl group. 4-Oxacholest-5-en-3-one (1) behaves similarly when treated with isopropylmagnesium bromide. Both 3-hydroxy-3-isopropyl-3(5 → 6βH)abeo-A-norcholestan-5-one and the isomeric diketone, 3-isopropyl-3,5-seco-A-norcholestan-3,5-dione (16) on contact with toluene-p-sulphonic acid in benzene give, in part, 4,4-dimethylcholest-5-en-3-one which is further converted into a mixture of aromatic hydrocarbons rich in 1,3,4-trimethyl-19-norcholest-1,3,5(10)-triene (25).