Potentially carcinogenic cyclopenta[a]phenanthrenes. Part VIII. Bromination of 17-ketones

Abstract

Bromination of 15,16-dihydrocyclopenta[a]phenanthren-17-one and its 11-methyl homologue gave the 15-bromo-and 15,15-dibromo-derivatives, even under conditions favouring aromatic bromination. N-Bromosuccinimide introduced bromine adjacent to the carbonyl group. Reductive tritiation of the 15-bromo-ketone gave the [15-³H]-derivative, but nucleophilic displacement of the bromine atom with sodium acetate in acetic acid led unexpectedly to the 16-acetoxy-17-ketone. Acid-catalysed hydration of the 15(16)-en-17-one, readily prepared by dehydrobromination of the 16-bromo-17-ketone with triethylamine, yielded the 15-hydroxyketone. The acetate of the latter was the major product from attempted bromination of the 17-ketone in the presence of thallium triacetate.