One-pot two-step reduction of CO2 with amines and NaBH4 to N-substituted compounds at atmospheric pressure

In this paper, the reductive N-formylation, methylation and cyclization of amines with carbon dioxide (CO2) using sodium borohydride (NaBH4) at atmospheric pressure, via a one-pot two-step procedure, is presented. Formato borohydride (NaBHn(OCHO)4-n), in situ formed in the reaction of NaBH4 with CO2, as an efficient agent to promote the corresponding reaction, and the mechanism is proposed on the basis of experiments. This wide substrate scope and simple operational methodology also facilitates the effective synthesis of formamides, methylamines, benzimidazoles and other heterocyclic compounds avoiding high temperature and pressure.