19.18: Preparation of Amines: Reductive Amination of Aldehydes and Ketones
Carbonyl compounds and primary amines undergo reductive amination first to produce imines, followed by secondary amines in the same reaction mixture, using selective reducing agents like sodium cyanoborohydride or sodium triacetoxyborohydride. Reductive amination produces different degrees of substitution of amines depending on the starting amine substrate.
Reductive amination using sodium cyanoborohydride as the reducing agent is called the Borch reaction. Sodium cyanoborohydride is a mild reductant that works under mildly acidic conditions.
Reductive amination has several applications, such as synthesizing the central nervous stimulant amphetamine and biosynthesis of the amino acid proline.