Carbon halogen-zinc exchange reaction

There are three classes of reaction that can generate the reactive haloalkylzinc species (1) Oxidative addition of zinc metal into a carbon-halogen bond, (2) alkyl group exchange between and organozinc reagent and a dihaloalkane, and (3) the insertion of a diazoalkane into a zinc iodide bond. 

Lithio-heterocycles have proved to be the most useful organometallic derivatives they react with the whole range of electrophiles in a manner exactly comparable to that of aryllithiums and can often be prepared by direct metallation (C-hydrogen deprotonation), as well as by halogen exchange between a halo-heterocycle and an alkyllithium. As well as reaction with carbon electrophiles, Uthiated species are often the most convenient source of heterocyclic derivatives of less electropositive metals, such as zinc, boron, silicon and tin, as will be seen in the following sections. 

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