Cobalt/diamine-catalyzed 1,1-difluoroethylation and 2,2,2-trifluoroethylation of aryl Grignard reagents with corresponding fluoroalkyl halides

Cobalt/diamine-catalyzed 1,1-difluoroethylation and 2,2,2-trifluoroethylation of aryl Grignard reagents with 1,1-difluoroethyl and 2,2,2-trifluoroethyl halides were investigated. With regard to the 1,1-difluoroethylation, 1,2-bis(dimethylamino)-2-methylpropane, which has been rarely used in the cross-coupling reactions, gave the highest yield among the diamine ligands tested. In the 2,2,2-trifluoroethylation, trans-1,2-bis(dimethylamino)cyclohexane provided the desired products in satisfactory yields with not only 2,2,2-trifluoroethyl iodide but also chloride. This Co/diamine catalyst was also effective for the coupling with other partially fluorinated alkyl halides in the presence of appropriate diamine ligands.