Insights into Naturally Occurring Compound Catalyzed Formylation and Methylation Reactions of Amines with CO2: The Origins of Chemoselectivity

Abstract

The mechanism of catalytic formylation and methylation of CO₂ with N-methylaniline and Ph₂SiH₂ is investigated using density functional theory (DFT) calculations. Two naturally occurring compounds (glycine betaine and lecithin) are used as catalysts, and the chemical selectivity of the reaction toward formamide, aminal, or methylamine products is analyzed. The formylation and methylation reactions are both initiated by successive CO₂ reduction with hydrosilane to give a stable species, diformyloxysilane [Si](OCHO)₂. Formamides are then generated upon the formylation of amines with the reduced CO₂ at low temperatures. At high temperatures, methylation occurs, leading to aminals and methylamine (prolonged reaction times). The real resting state of the entire process is diformyloxysilane [Si](OCHO)₂, as it has strong electrophilicity, which promotes the investigated reactions. All of the active catalysts of CO₂ reduction studied herein possess a zwitterionic structure with a negatively charged oxygen atom that can activate the Si–H bond in hydrosilane.