Abstract
Non-ligated Nickel (II) chloride-catalyzed cross-coupling between aryl Grignard reagents and aryl halides has some merits for industrial application. 1) Toxic and expensive phosphines are not needed and 2) the absence of organic ligands makes the treatment of the reaction mixture easier: The extraction with water is enough to separate the product from the catalyst. We examined the problems for the industrial scale application of the NiCl2-catalyzed cross-coupling reaction for the production of 3-chloro2-methylbiphenyl, an intermediate for pyrethroid insecticides, from 2, 6-dichlorotoluene and bromobenzene.
The undesired formation of bis (magnesium chloride) from 2, 6-dichlorotoluene can be avoided by using excess 2, 6-dichlorotoluene. The unreacted 2, 6-dichlorotoluene can be recovered by distillation after the reaction. Homo-coupling of Grignard reagents can be suppressed by the purge of oxygen from the reaction system.
