DIC-borane-catalyzed selective methylation of primary amines with CO2 using boranes as reducing agents

The selective reductive N-methylation and N,N-dimethylation of primary amines using CO2 are some of the most significant challenges faced by organic chemists. Herein, we report the highly selective N,N '-diisopropylcarbodiimide-catalyzed methylation of primary amines using 1 atm CO2 under metal-free conditions. Borane-piperazine and borane-trimethylamine complexes were used as reducing agents for the N-methylation and N,N-dimethylation of various aromatic primary amines, respectively, in the presence of CO2. Mechanistic studies suggest that the selectivity of methylation is controlled by the steric effects of amines and boranes.

Automated summary

The selective reductive N-methylation and N,N-dimethylation of primary amines using CO2 is challenging. This study reports a highly selective N,N'-diisopropylcarbodiimide-catalyzed methylation of primary amines using 1 atm CO2 under metal-free conditions. The selectivity of methylation is controlled by the steric effects of amines and boranes.