Organozinc reagents copper iodide

RCu(CN)ZnI.u These new copper reagents are prepared by reaction of primary or secondary iodides with zinc that has been activated with 1,2-dibromoethane and chlorotrimethylsilane. The resulting organozinc compounds are then allowed to react with the THF-soluble CuCN-2LiCl (equation I). Because of the mild conditions, these new reagents can be prepared from iodides containing keto, ester, and nitrile groups. 

The preparation of alkylzinc iodides is facilitated if the reaction is performed in THF and NMP mixtures. Such solutions of Me02C(CH2)4ZnI add to benzaldehyde in the presence of TMSCI (2 equiv.) in 70% yield.33 The use of ultrasound also promotes the formation of organozinc compounds.34>34a 34e This procedure proved to be especially useful for the preparation of Jackson reagent 6 derived from serine. In the presence of a copper(l) or palladium(O) catalyst, this zinc derivative reacts with various electrophiles (Scheme 1) 3S,3Sa-3Sj 0f z nc reagent 7 leading to methyl but-3-enoate and the zinc amide... 

The introduction of a polyfluorinated chain is not so easy as that of an alkyl chain. Transition metal catalyzed cross-coupling of Grignard reagents and organozinc compounds are inefficient in the synthesis of polyfluorinated 3-alkylthiophene. The copper-catalyzed perfluoroalkylation results in the formation of 2-and 3-substituted thiophenes, which are difficult to separate from each other. The reaction of fluorinated alkylmagnesium iodide with 3-formylthiophene, follwed by reduction with lithium aluminum hydride, gave (22) in an overall yield of 40% [27]. 

The uncatalyzed reaction of acid chlorides with organozincs is sluggish and inefS-cient. It is often complicated by side reactions and leads usually to low yields of the desired acylation products. In contrast, the CuCN 2LiCl-mediated acylation of various zinc reagents affords ketones in excellent yields. The reaction of the zinc-copper reagent 328 obtained by the direct zinc insertion to the iodide 329 followed by a transmetallation with CuCN 2LiCl reacts with benzoyl chloride at 25 °C leading to the ketone 330 in 85% yield [52b]. The functionalized benzylic bromide 331... 

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