Chemoselective synthesis of tertiary and secondary amines by reductive amination of aldehydes

A simple and efficient catalyst-free chemoselective reductive amination of primary amines and aldehydes to synthesis of tertiary and secondary amines with borane complex was developed. Primary amines are converted into tertiary and secondary amines in one pot reaction under mild condition with good functional group compatibility and It does not require any catalyst to participate in this reaction. The chemoselective control was achieved by switching the steric hindrance of borane complex. The strategy was successfully applied to synthetize Tetracaine (anaesthetic) and the potential mechanism was verified by isotope labeling experiments.