Direct synthesis of amides from nitroarenes and carboxylic acids via CO-mediated reduction

A highly efficient direct carbon monoxide-mediated protocol for converting nitroarenes and carboxylic acids to amides was developed. Investigation of the reaction kinetics and a Hammett study allowed us to reveal the reaction mechanism and the best reaction conditions. An observed apparent partial reaction order by nitroarene in this reaction is 0.5 indicating the switch of the rate-determining step during the course of the reaction. A highly valuable Vorinostat precursor with 99% purity was synthesized in a quantitative yield without any purification; the E-factor of the process was 0.35, which fits to the multiton chemistry reactions. All substrate scope was prepared using the simple Ru3(CO)12 as a catalyst, and TON up to 44,400 was achieved.