Steroids and Walden inversion. Part LXIV. A reinvestigation of the deamination of 2-, 4-, and 7-amino-5a-cholestane

Abstract

Equatorial 2α-, 4α- and 7β-amino-5α-cholestane are deaminated in acetic or aqueous acetic acid with predominant but not exclusive retention accompanied by some elimination. Axial 4β- and 7α-amino-5α-cholestane are deaminated mainly with elimination, probably owing to the adjacent tertiary 5α- or 8β-hydrogen atom. 2β-Amino-5α-cholestane undergoes considerable elimination but also yields alcohols with predominant retention and acetates with predominant inversion. The ratio of epimeric alcohols formed differs considerably from the ratio of epimeric acetates produced in all these deaminations.

The deamination process appears to be a complex reaction, greatly influenced by steric environment, which proceeds by a combination of S_Ni, S_N2, and E2 mechanisms involving the diazonium ion, and by S_N1 and E1 mechanisms involving the intermediate solvated carbonium ion.