Carboxylate-promoted reductive functionalization of CO2 with amines and hydrosilanes under mild conditions

Abstract

Various oxygen-nucleophiles especially carboxylates, e.g. cesium/tetrabutylammonium carboxylate, were proved to be efficient and selective catalysts for reductive functionalization of CO₂ with amines and hydrosilanes to methylamines. Various amines including aromatic and aliphatic, primary and secondary ones were methylated successfully in the presence of diphenylsilane as the reductant under 50 °C and an atmospheric pressure of CO₂. Furthermore, a reaction pathway involving CO₂ reduction to the C⁰ species i.e. aminal rather than the formamide as the intermediate was proposed. This protocol represents a transition metal-free and environmentally friendly option for CO₂ conversion to useful chemicals via the formation of C–N bonds coupled with six-electron reduction of CO₂ to the methanol level under mild conditions.