Aryl halides organocuprates

The alkyl or aryl halide -organocuprate coupling disconnection is... 

Coupling of the organocuprate with an alkyl, vinyl, or aryl halide ... 

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). 

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)). 

Organocuprate reagents also couple with aryl and vinyl halides to make substituted benzenes and elongated alkenes. Recent research has developed many additional coupling methods using other transition metals in the reagents and catalysts. 

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