NON-LIGATED NICKEL CHLORIDE-CATALYZED CRO SS-COUPLING OF ARYL GRIGNARD-REAGENTS WITH HALOARENES - SYNTHESES OF ASYMMETRIC TERARYLS

The reaction between aryl Grignard reagents and aryl halides in the pr esence of non-ligated nickel(II) chloride (NiCl2) affords the cross-co upling products in high yields. It is found that NiCl2 effectively cat alyzes the coupling of aryl Grignard reagents with bromoarenes, but it has a low catalytic activity towards chloroarenes. The high halogen-s electivity which was not found in the reactions using phosphine-ligate d nickel complexes is a unique feature of the NiCl2-catalysis for the cross-coupling reaction. By the halogen-selectivie NiCl2-catalyzed cro ss-coupling, we synthesized unsymmetrical terphenyls, which are import ant materials for a heat-stable polymer. On the other hand, for the cr oss-coupling reactions of heteroaromatics, NiCl2 was not act as an act ive catalyst, but the cross-coupling reaction of thienylmagnesium hali des with chloroiodobenzene proceeded selectively to give (chlorophenyl )thiophenes.