Preparation of organozinc halides using in situ activated zinc

Preparation of organozinc halides using in situ activated zinc 

The realization that zinc dust can be activated by treatment, sequentially, with 1,2-dibromoethane and chlorotrimethylsilane, has had a significant impact on 

However, for other palladium catalysed reactions of organozinc iodides with electrophiles, THF is a good choice of solvent. The incompatibility of THF and acid chlorides at ambient temperature can also be overcome, in some cases, by the use of a carbonylative cross-coupling in which an iodobenzene derivative is used as the precursor.17 

The application of organozinc iodides prepared in THF is illustrated in Protocols 4 and 5, which describe the palladium catalysed cross-coupling of a serine-derived organozinc iodide with a vinyl iodide, and the palladium catalysed carbonylative cross-coupling of another serine-derived organozinc iodide with a functionalized aromatic iodide. In the reaction with the vinyl iodide, it is important to transfer the solution of the organozinc iodide from the residual zinc, since this can react unproductively with the electrophile. In the case of the carbonylative coupling with the functionalized aromatic iodide, such a transfer is unnecessary, since the zinc does not react with the electrophile under the reaction conditions. These two protocols also illustrate how to conduct such reactions on different scales. 

Preparation of a serine-derived organozinc iodide in THF, and coupling with methyl 3-iodopropenoate 

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