Halides, aryl reaction with organocuprates

Similarly to the alkyl derivatives, the most common route for arylcopper compounds is the reaction of a copper halide and aryllithium compounds (Equation (4)). Organocuprates with aryl groups are obtained by using an appropriate excess of the lithium reagent. Magnesium aryls have also been employed in transmetallation reactions with Cu(l) salts to yield both arylcopper compounds and arylcuprates (Equations (5) and (6)). 

Organocuprates can react with all alkyl halides except tertiary alkyl halides. Because they can react with vinylic halides and aryl halides (an aryl hahde has a hydrogen attached to a benzene ring), they can be used to prepare compounds that cannot be prepared by Sn2 reactions with Grignard reagents or organolithium compounds. (Remember that vinylic and aryl halides cannot undergo nucleophilic attack Section 9.5). 

Reaction of an organocuprate with an aryl halide or a vinyl halide (12.2). 

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