Preparation of Organozinc Halides

Sdieme 2.2S. Preparatior of a furctlorallzed arylzirc halide by trarsmetalatior of ar orgaro-magresium compourd. 

Sdietne 2.37. Substitution reactions of propar lic bromides and unsaturated epoxides with organ ozinc reagents. 

Alkynylation of zinc-copper compounds has been used for the synthesis of polyfunctional acetylenic ethers [84] and for the preparation of building blocks for pharmaceutically active compounds [85]. Whereas cross-coupling between non-activated iodoalkenes and zinc-copper reagents only proceeds at elevated temperatures and in polar solvents such as NMP or DMPU (60 12 h) [86], alkenyl 

The reaction between zinc-copper reagents and acid ciilorides is very general and provides a useful synthesis of ketones [7 34 41 42]. This acylation has also been used to prepare various indoles substituted in position 2 (Sdieme 2.42) [88]. 

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Preparation of organozinc halides using transmetalation reactions. . . 296... 

The most significant obstacle to be overcome in the preparation of organozinc halides by direct insertion of zinc metal into an organic halide is the intrinsic lack of reactivity of commercially available zinc metal. This is primarily due to a surface coating, for example of zinc oxide, which prevents direct reaction with an organic substrate. The success of attempts to insert zinc metal into an organic halide is entirely dependent upon the care with which the zinc metal is... 

I 2 Transmetafatton Reactions Producing Organocopper Reagents 2.4.1.1 Preparation of Organozinc Halides... 

A major part of this chapter will show the synthetic applications of these transmetallation reactions for the perfonnancc of cross-coupling reactions. After a short description of the methods of preparation of organozinc halides (RZnX) and diorganozincs (R2Zn), the utility of these reagents for forming new carbon-carbon bonds will be presented. Emphasis will be... 

Scheme 4.5 Preparation of organozinc halides from organolithium reagents by transmetal-lation with zinc salts [46-49].

Preparation of Organozinc Halides using Transmetallation Reactions... 

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