Efficient N-formylation of carbon dioxide and amines with alkanolamine as eco-friendly catalyst under mild conditions

The catalytic fixation of greenhouse gas CO 2 has been a hot topic of research, in which the reduction and functionalization of CO 2 is important for application. In present work, cheap and readily available alkanolamines were used as efficient catalysts with phenylsilanes as reducing agents to achieve the N-formylation reaction by constructing C-N bonds via the reaction between CO 2 and amines (aliphatic or aromatic amines) under mild conditions (40℃and 0.1 MPa). Further studies showed that present catalytic system has wide substrates application. Mono-N-formylated compounds were obtained as main products with good to high yields for all amines. It is worthy noted that for p-aminobenzylamine containing two amino groups as substrate, both amino groups are formylated and N-formylation reaction occurs mainly in aliphatic amine with high electron cloud density. Scale-up research has been performed effectively with high conversion of amine (80%) to obtain the mono-formylated product selectively. Finally, the mechanism of the reaction between amine and CO 2 is proposed via control experiments and spectra verification. Systematic mechanism studies have revealed that after polarization by polar solvent DMSO, N-methyldiethanolamine activates CO 2 by forming internal salts, which are subsequently reduced by phenylsilanes to formoxysilane intermediates and finally to form N-formylated products.