Carboxylation of Organoboronic Esters Catalyzed by N‐Heterocyclic Carbene Copper(I) Complexes

An excellent N-heterocyclic carbene copper(I) catalyst system for the carboxylation of aryland alkenylboronic esters with CO2 is reported, which not only showed higher functional-group tolerance, but could also afford structurally characterizable active catalyst species, thus offering unprecedented insight into the mechanistic aspects of the catalytic process.

Abstract

Copper complexes with a CO2 fixation: Copper(I) complexes serve as excellent catalysts for the carboxylation of aryl- and alkenylboronic esters with CO2, affording a variety of functionalized carboxylic acid derivatives (see scheme). Important active intermediates such as the copper(I) aryl and carboxylate complexes, [(IPr)CuR] and [(IPr)CuOCOR] (R=4-MeOC6H4, IPr=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), are isolated and structurally characterized.