Reactive zinc organozinc reagent synthesis

The synthesis of functionalized zinc organometallics can be accomplished with a variety of methods that have been developed in recent years. The intrinsic moderate reactivity of organozinc reagents can be dramatically increased by the use of the appropriate transition metal catalyst or Lewis acid. Furthermore, the low ionic character of the carbon-zinc bond allows the preparation of a variety of chiral zinc organometallics with synthetically useful configurational stability. These properties make organozinc compounds ideal inteimediates for the synthesis of complex and polyfunctionalized organic molecules. 

Metallation of l-methoxy-2-butyne with n-butyllithium at -78 C, followed by the addition of one equivalent of zinc chloride, generates the very reactive and unisolable organozinc intermediate. Reaction of this zinc reagent with cyclohexenone affords the alkynic alcohol in 95% yield as a 65 35 mixture of diasteieomers. Subsequent reduction of the triple bond provides either the trans alkene or the cis alkene, depending on the reaction conditions. A modified oxy-Cope rearrangement thus provides the dia-steieomeric ketones, which have been used for the synthesis of juvabione (Scheme 29). ... 

Coupling of organozincs with aryl halides. The method is very useful for the synthesis of biaryls,including heterobiaryls.Vinylic, " aliphatic zinc reagents, and even Zn(CN>2 are reactive toward ArX in the presence of (Ph3P)4Pd. Perfluoro-alkenylzinc bromides and cyclopropenylzinc chlorides also couple efficiently with iodoarenes. 

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