Catalyst free N-formylation of aromatic and aliphatic amines exploiting reductive formylation of CO2 using NaBH4

Abstract

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 CO₂ with sodium borohydride generates formoxy borohydride species in situ, as confirmed by ¹H and ¹¹B 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 CO₂ with amine leading to N-formylation of amines.