Natural Product Glycine Betaine as an Efficient Catalyst for Transformation of CO2 with Amines to Synthesize N-Substituted Compounds

Transformation of carbon dioxide (CO2) into value-added chemicals is of great importance, and use of natural products as a catalyst is very interesting. Herein, we used the naturally occurring glycine betaine as an efficient and renewable catalyst for the formation of a C-N bond between CO2 and amines using PhSiH3 as the reductant. The effects of different factors on the reaction were studied. It was demonstrated that the catalyst was very active for the reactions, and a broad range of amine substrates could be converted with satisfactory yields. Moreover, the selectivity to different N-substituted compounds could be controlled by the molar ratio of reactants (i.e., CO2, amines, and PhSiH3) and the reaction temperature. In the catalytic cycle, the carbon oxidation state of CO2 could be reduced to +2, 0, and -2, respectively, and thus, the corresponding formamides, aminals, and methylamines were produced via successive two-electron reduction steps.