Spiro steroids via the Barbier–Grignard reaction of steroidal ketones with allyl bromide and magnesium

Abstract

Barbier–Grignard reaction of 3- and 17-steroidal ketones gave excellent yields of the allyl steroids 1 + 2 and 15. These were transformed into a mixture of 1,3- and 1,4-diols by hydroboration–oxidation. The diols 3,5, and 18 were used for the preparation of spirolactones and spiroethers. Thus, the Barbier–Grignard allylation–hydroboration–cyclization sequence proved to be an effective method for the spiroannelation of steroidal ketones. It was also shown that an earlier assignment of the stereochemistry of the diols 3 and 5 was erroneous.