An expedient strategy of reductive N-alkylation of amines with readily available carboxylic acids as alkylating reagents has been developed. Commercially available and hydrogen rich ammonia borane (H3B·NH3) was employed as a practical hydrogen source. Mono- and dialkylated products of primary amines could be selectively obtained by varying the reaction conditions. Complementary to known reductive aminations, this strategy showed excellent functional group compatibility, and a broad range of secondary and tertiary amines, including drug molecules, were obtained smoothly.
