A residue-free production of biaryls using supported gold nanoparticles

Small gold nanoparticles in the presence of O-2 are able to cleave C-H bonds of non-activated arenes and facilitate catalytic formation of biaryls under mild conditions. This procedure avoids the common requirement of iodine, acids, bases, and/or other stoichiometrical additives to accomplish multiple turnovers and results in a zero-waste synthetic process. A number of unactivated arenes such as benzene, toluene, p-xylene, nitrobenzene, chlorobenzene, or phenol are selectively converted to the corresponding biaryls, with accumulated turnover numbers greater than 600. Kinetic measurements, in combination with IR, HRTEM, and STEM-HAADF data, suggest that the reaction takes place on gold atoms that are metallic in character, with the highest C-C bond formation rate provided by gold nanoparticles of approximately 3 nm of diameter. A radical-free reaction mechanism is postulated on the basis of the kinetic measurements. The results represent a first stone for the waste-free preparation of biaryls using supported gold catalysts. (C) 2014 Elsevier Inc. All rights reserved.