A CO-Catalyzed Transamidation Reaction.

Transamidation reactions are often mediated by reactive substrates in the presence of overstoichiometric activating reagents and/or transition metal catalysts. Here we report the use of CO as a traceless catalyst: in the presence of catalytic amounts of CO, transamidation reactions were accelerated with primary, secondary, and tertiary amide donors. Various amine nucleophiles including amino acid derivatives were tolerated, showcasing the utility of transamidation in peptide modification and polymer degradation (e.g., Nylon-6,6). In particular, ,-dimethylhydroxyl amides (Weinreb amides) displayed a distinct reactivity in the CO-catalyzed transamidation versus a N atmosphere. Comparative Hammett studies and kinetic analysis were conducted to elucidate the catalytic activation mechanism of molecular CO, which was supported by DFT calculations. We attributed the positive effect of CO in the transamidation reaction to the stabilization of tetrahedral intermediates by covalent binding to the electrophilic CO.