Catalyst-free hierarchical reduction of CO2 with BH3N(C2H5)3 for selective N-methylation and N-formylation of amines

We describe herein an efficient and catalyst-free methodology for N-formylation and N-methylation of various amines using BH3N(C2H5)3 as a reductant and CO2 as C1 source. This system is compatible with a wide range of substrates, such as aromatic secondary amines, aliphatic secondary amines, heterocyclic amines, and primary amines. The desired methylamines and formamides are obtained in excellent yields by changing the reaction solvent, temperature, and the amount of BH3N(C2H5)3. The optimum yields of methylamines and formamides are up to 99 %, which are comparable to the data using different catalysts. Moreover, it has been demonstrated by mechanistic research that CO2 was activated by inserting into B–H bonds of BH3N(C2H5)3 and formamide can be regarded as an intermediate species during the N-methylation formation.