Organocopper compounds, reactions with alkyl halides

While a large number of studies have been reported for conjugate addition and Sn2 alkylation reactions, the mechanisms of many important organocopper-promoted reactions have not been discussed. These include substitution on sp carbons, acylation with acyl halides [168], additions to carbonyl compounds, oxidative couplings [169], nucleophilic opening of electrophilic cyclopropanes [170], and the Kocienski reaction [171]. The chemistry of organocopper(II) species has rarely been studied experimentally [172-174], nor theoretically, save for some trapping experiments on the reaction of alkyl radicals with Cu(I) species in aqueous solution [175]. 

The consensus favors a transitory copper(III) intermediate in the reaction of a copper corapound with an alkyl or vinyl halide 37, 57, 65, 185, 297), although Tamura and Kochi consider such an intermediate unlikely for alkyl halides (276). Collman (57) has suggested that organocopper compounds are representative of a number of transition... 

There is presumably more than a subtle difference between the reactions of alkyl and aryl halides with organocopper compounds, as a straightforward nucleophilic displacement of aryl halide by the d electrons of a copper species is hardly likely. Simple aryl halides are nearly all inert to the usual nucleophiles, such as alkoxides, unless strongly activated by electron-attracting groups in the ortho and para positions. However, coordination of the halogen to copper may be sufficient to... 

In this chapter, the substitution reactions of organometallic reagents with organic halides and related electrophiles are reviewed. - The major portion of the chapter is devoted to a discussion of organocopper compounds, which first transformed the alkylation of nonstabilized carbanions into a reaction of general synthetic utility. More recently, transition metals other than copper have also found widespread application in such coupling reactions, and developments in this area are outlined in Section 1.5.3. 

The organocopper compounds react mainly with halides and they also react with aryl compounds, acetals, tosylates (R-0S02-C6H4CH3(-/7)) and tolyflates (R-OSO2CF3). The reactions with halides are first order to each of the concentrations and they are Sn2 reactions. The order of reactivity of alkyl halides regarding the alkyl group is as follows ... 

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