Catalyst free N -formylation of aromatic and aliphatic amines exploiting reductive formylation of CO 2 using NaBH 4 .

Herein, we report a sustainable approach for N -formylation of aromatic as well as aliphatic amines using sodium borohydride and carbon dioxide gas. The developed approach is catalyst free, and does not need pressure or a specialized reaction assembly. The reductive formylation of CO 2 with sodium borohydride generates formoxy borohydride species in situ , as confirmed by 1 H and 11 B NMR spectroscopy. The in situ formation of formoxy borohydride species is prominent in formamide based solvents and is critical for the success of the N -formylation reactions. The formoxy borohydride is also found to promote transamidation reactions as a competitive pathway along with reductive functionalization of CO 2 with amine leading to N -formylation of amines.