Reactivity aryl organozinc reagents

Crucially, this allows organozinc reagents to be prepared from less reactive aryl bromides and secondary or tertiary alkyl bromides. Alternatively, organozinc iodides can be prepared by means of a palladium(0)-catalyzed reaction between alkyl iodides and Et2Zn (Scheme 2.25) [53-56]. 

A prototypical study for this section has been obtained as early as in 1983 for carbonylative cross-coupling of the mixture of aryl iodide and alkyl iodide in the presence of Zn metal and palladium catalyst. This system apparently works due to differences of reactivity of aryl versus alkyl iodide toward metallation by Zn. Further studies were rather scarce to involve only preformed functionalized alkylzincs. Carbonylative cross-coupling of functionalized organozinc reagents with allylic esters and GO (1 atm) can be carried out in THF in the presence of HMPA, which suppresses side-reactions (Scheme 4). ... 

Organozinc reagents. Zn-Cu couple often shows higher reactivity than zinc dust towards alkyl halides. Thus perfluoroalkylzinc iodides are rapidly formed in the presence of AIBN, and quenching such reagents in situ by DMF gives perfluoroalkyl aldehydes. (Note that Zn-Ag on graphite is well suited for the preparation of aryl-zinc species). ... 

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