Betaine Catalysis for Hierarchical Reduction of CO with Amines and Hydrosilane To Form Formamides, Aminals, and Methylamines.

An efficient, sustainable organocatalyst, glycine betaine, was developed for the reductive functionalization of CO with amines and diphenylsilane. Methylamines and formamides were obtained in high yield by tuning the CO pressure and reaction temperature. Based on identification of the key intermediate, that is, the aminal, an alternative mechanism for methylation involving the C silyl acetal and aminal is proposed. Furthermore, reducing the CO amount afforded aminals with high yield and selectivity. Therefore, betaine catalysis affords products with a diversified energy content that is, formamides, aminals and methylamines, by hierarchical two-, four- and six-electron reduction, respectively, of CO coupled with C-N bond formation.