Steroids and Walden inversion. Part LXII. The chlorination of 5α-cholestan-1-one

Abstract

Monochlorination of 5α-cholestan-1-one is slow and yields 28% of the axial 2β-chloro-ketone and 32% of the equatorial 2α-chloro-ketone under conditions in which the 2β-chloro-ketone undergoes inversion to the extent of 49%; the values, 28 and 32%, take account of this transformation caused by acid-catalysed enolisation. Monochlorination of the axial 2β-chloro-ketone to give the 2,2-dichloro-ketone is virtually quantitative at 20° after 30 hours, whereas the equatorial 2α-chloro-ketone under the same conditions yields only 12% of the 2,2-dichloroketone after 96 hours. The more significant u.v., i.r., o.r.d., and n.m.r. characteristics of the above chloro-ketones and some related compounds are recorded.