The Mechanism of Lithium Aluminum Hydride Reduction of 13α-Steroidal 16, 17-Bromohydrins

Abstract

The reaction mechanism of lithium aluminum hydride reduction was investigated with the 13α-steroidal 16, 17-bromohydrins by means of tracer technique. The epimeric cis-bromohydrins were primarily led to the ketone resulting from hydride shift and then further reduced to the 17-hydroxylic compounds, where"mixed hydride"produced from the released bromide and lithium aluminum hydride would play a role of reducing agent. On the other hand the trans-bromohydrin was reduced to the corresponding alcohol by direct displacement of the halogen with hydride. Based upon these experimental results feasibility of the pathway involving reduction of the halohydrin in the five-membered ring has been discussed.