Catalyst-Free N-Formylation of Amines Using Formic Acid as a Sustainable C1 Source

Formic acid, as an easily available C1 source, can be obtained through CO2 hydrogenation or biomass smelting. For this perspective, N-formylation of amines with formic acid as the C1 synthon can be considered as indirect utilization of CO2 or biomass, thus providing an alternative synthetic strategy. In this work, we present a sustainable protocol for the N-formylation of amines using formic acid as the carbonyl source under catalyst-free conditions. This procedure yields medium to excellent results for various formamides. Furthermore, we successfully extended this protocol to include the reduction coupling of formic acid, primary amines, and aldehydes, demonstrating broad substrate applicability.