Joseph R. Martinelli

Palladium-Catalyzed Carbonylation Reactions of Aryl Bromides at Atmospheric Pressure : A General System Based on Xantphos

A method for the Pd-catalyzed carbonylation of aryl bromides has been developed using Xantphos as the ligand. This method is effective for the direct synthesis of Weinreb amides, primary and secondary benzamides, and methyl esters from the corresponding aryl bromides at atmospheric pressure. In addition, a putative catalytic intermediate, (Xanphos)Pd(Br)benzoyl, was prepared and an X-ray crystal structure was obtained revealing an unusual cis-coordination mode of Xantphos in this palladium-acyl complex.

Experimental Limiting Oxygen Concentrations for Nine Organic Solvents at Temperatures and Pressures Relevant to Aerobic Oxidations in the Pharmaceutical Industry

Applications of aerobic oxidation methods in pharmaceutical manufacturing are limited in part because mixtures of oxygen gas and organic solvents often create the potential for a flammable atmosphere. To address this issue, limiting oxygen concentration (LOC) values, which define the minimum partial pressure of oxygen that supports a combustible mixture, have been measured for nine commonly used organic solvents at elevated temperatures and pressures. The solvents include acetic acid, N-methylpyrrolidone, dimethyl sulfoxide, tert-amyl alcohol, ethyl acetate, 2-methyltetrahydrofuran, methanol, acetonitrile, and toluene. The data obtained from these studies help define safe operating conditions for the use of oxygen with organic solvents.

Cu-Catalyzed Aerobic Oxidative N–N Coupling of Carbazoles and Diarylamines Including Selective Cross-Coupling

A Cu-catalyzed method has been identified for aerobic oxidative dimerization of carbazoles and diarylamines to the corresponding N-N coupled bicarbazoles and tetraarylhydrazines. The reactions proceed under mild conditions (1 atm O2, 60-80 °C) with a catalyst composed of CuBr·dimethylsulfide and N, N-dimethylaminopyridine. Reactions between carbazole and diarylamines show unusually selective cross-coupling, even with a 1:1 ratio of the two substrates. This behavior was found to arise from reversible formation of the tetraarylhydrazine. Formation of this species is kinetically favored, but cleavage of the N-N bond under the reaction conditions leads to selective formation of the thermodynamically favored cross-coupling product.