Efficient synthesis of sterically crowded biaryls by palladium-phosphinous acid-catalyzed cross-coupling of aryl halides and aryl grignards

[GRAPHICS] A series of sterically hindered biaryls have been obtained by palladium- and nickel-phosphinous acid-catalyzed Kumada-Corriu cross-coupling of ortho-substituted aryl halides and Grignard reagents. This method allows formation of di- and tri-ortho-substituted biaryls in 87-98% yield under mild reaction conditions even when electron-rich aryl chlorides are used. The reaction also proceeds with aryl iodides at -20 degrees C, and under these conditions, functional groups that are generally not compatible with Grignard reagents are tolerated.