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

Transformation of carbon dioxide (CO 2 ) 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 CO 2 and amines using PhSiH 3 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., CO 2, amines, and PhSiH 3 ) and the reaction temperature. In the catalytic cycle, the carbon oxidation state of CO 2 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.