Reductive amination, also termed reductive alkylation, is one of the most popular methods for forming C-N bonds. The pivotal Borch reaction, disclosed in 1971, laid the groundwork for borohydride-promoted reductive amination. This reaction leverage sodium cyanoborohydride (NaBH3(CN)) as a reducing reagent to condense a ketone/aldehyde with an amine/aniline, forming a C-N bond.
The reduction potential of NaBH3(CN) can be judiciously orchestrated by adjusting the pH of the reaction mixture. The iminium, an intermediate of reductive amination, is readily reduced to an amine at pH 6, at which the reduction of the ketone/aldehyde barely occurs.
The seminal paper by Borch elucidated the reaction properties of NaBH3(CN) in a meticulous manner, which are encapsulated in the post.
