Bismuth(III) salt-catalyzed Westphalen and backbone rearrangements of 5β,6β-epoxysteroids -: Synthesis and structural elucidation of new olefinic 19-nor and 18,19-dinorsteroids

A new process using the ecofriendly bismuth(III) salts as catalysts for the Westphalen and backbone rearrangements of 5 beta,6 beta-epoxysteroids is reported. This method is particularly sensitive to changes on solvent, temperature, stereochemistry of starting epoxysteroid, and its substituent at C17. Depending on the reaction conditions, either Westphalen-type or backbone rearranged products were obtained, all being 3 beta-acetoxy-6 beta-hydroxy-substituted. Several new olefinic 19-nor and 18,19-dinorsteroids were obtained and their structural elucidation was fully accomplished using 2D NMR and X-ray crystallography techniques. (C) 2008 Elsevier Inc. All rights reserved.