Steroids and Walden inversion. Part LXIII. Substitution reactions of the 5α-cholestan-4-ols: a further example of Walden retention

Abstract

5α-Cholestan-4α-ol reacts with phosphorus pentachloride or thionyl chloride to give 4α-chloro-5α-cholestane with much elimination product, and with phosphorus pentabromide at 0° it gives 4α-bromo-5α-cholestane, in each case with retention of configuration. 5α-Cholestan-4β-ol, with phosphorus pentachloride or phosphorus pentabromide in chloroform at 20°, or with thionyl chloride, yields mainly cholest-4-ene; use of phosphorus pentachloride in benzene at 80° gives 4β,5α-dichlorocholestane.