Δ16-20-Ketosteroids by C2-Elongation from Δ16-17-Substituted Steroids

Article abstract of DOI:10.1002/prac.19933350508

Reactions of corticoid precursor steroids with a Δ¹⁶-double bond and iodine, trimethylsilyl, tributylstannyl or trifluoromethanesulfonyloxy groups in 17-position were studied with the aim of introducing an acyl substituent in 17-position.Starting with the 17-trimethylsilyl compounds, using acyl chlorides and AlCl3 as a catalyst, a mixture of chlorinated compounds were obtained, among others.Better results gave palladium-catalyzed reactions, such as the cross-coupling of 17-tributylstannyl compounds with acyl chlorides or the substitution of the 17-iodides or the 17-triflates by vinyl ethers.In the reaction of the 17-iodides, different protecting groups are tolerated; thus this method is of general use.No Δ¹⁶-17-triflates were obtained by the reaction of androsta-4-ene-3,17-dione or androsta-1,4-diene-3,17-dione with trifluoromethanesulfonyl anhydride.This is a limitation of the triflate method, which in the other cases gives the best yields (>80percent).