Neighbouring hydroxy-group participation in the reductive elimination of chlorine from 5α,6β-dichlorocholestanes with sodium borohydride

Abstract

Sodium borohydride-promoted, reductive elimination of chlorine from 5α,6β-dichlorocholestane and some of its derivatives has been studied in propan-2-ol. The presence of a 3α-hydroxy-group in the steroidal skeleton strongly accelerates the process, and evidence is given for an intramolecular, electrophilic, assisted reaction. Various mechanisms for the reductive elimination are discussed and an E2 mechanism is proposed for the reaction of the 1,2-dichlorides.