The Kumada-Corriu Coupling And Homocoupling Of Grignard Reagents

The Kumada-corriu cross-coupling reaction and homocoupling reaction of Grignard reagents as the most efficient methods for the construction of carbon-carbon bonds have been widely applied in a wide range of pharmaceuticals, natural products, polymers, and liquid crystal materials. Thus, the synthesis and preparation of biaryls has been very significant.It was reported that in this paper the Kumada-corriu cross-coupling reactions of halogeno benzene with Grignard reagents were catalyzed by palladium nanoparticles, which was prepared according to Kwon’s report. The extending reactions gave good yields and more importantly, the catalyst was highly active, a novel and moisture-stable, which was successfully applied in the couplings of arylboronic acids with aryl halides and arenediazonium tetrafluoroborate salts by our group. The reaction conditions were optimized focused on the Pd/Al(OH)3 loading, solvent, solvent dose and temperature. After all these extensive experiments it was discovered that when reactions were performed on a 0.2 mmol scale of iodobenzene, the optimal conditions employed 0.07 mol% Pd and 1.25 equiv. of phenylmagnesium bromide in 1.0 mL toluene for 24 h at 40 ℃ which provided biphenyl in 96% isolated yield. It was shown that whatever the electronic and the steric nature of the cross-coupling partners, most of the reactions gave products in good to excellent yields.In this paper the homocoupling reactions of Grignard reagents were respectively catalyzed by Pd(OAc)2、Ni(OAc)2、CuI、Fe3O4 and I2. The reaction conditions were optimized focused on the catalyst loading, oxidant type and amount, solvent, solvent dose and temperature. Finally we gained the optimized conditions of the five catalytic system, and a variety of aryl Grignard reagents could quickly transform to the desired corresponding symmetrical biaryls under the optimized conditions.The products were determined by TLC, IR,1HNMR.