?16-20-Ketosteroide durch C2-Verl�ngerung aus ?16-17-substituierten Steroiden
摘要:
Reactions of corticoid precursor steroids with a DELTA16-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 DELTA16-17-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 (> 80 %).