Coupling reactions of organocuprate reagents

Scheme 8.1 gives several examples of the use of coupling reactions of organocuprate reagents with halides and acetates. Entries 1 to 3 are examples of the... 

The most frequently used organocuprates are those m which the alkyl group is pri mary Steric hindrance makes secondary and tertiary dialkylcuprates less reactive and they tend to decompose before they react with the alkyl halide The reaction of cuprate reagents with alkyl halides follows the usual 8 2 order CH3 > primary > secondary > tertiary and I > Br > Cl > F p Toluenesulfonates are somewhat more reactive than halides Because the alkyl halide and dialkylcuprate reagent should both be primary m order to produce satisfactory yields of coupled products the reaction is limited to the formation of RCH2—CH2R and RCH2—CH3 bonds m alkanes... 

Alkanes can also be prepared from alkyl halides by reduction, directly with Zn and acetic acid (AcOH) (see Section 5.7.14) or via the Grignard reagent formation followed by hydrolytic work-up (see Section 5.7.15). The coupling reaction of alkyl halides with Gilman reagent (R 2CuLi, lithium organocuprates) also produces alkanes (see Section 5.5.2). 

The first organometallic compounds used in coupling reactions were Gilman reagents, also called organocuprates. They are prepared by the reaction of an organolithium reagent with cuprous iodide in diethyl ether or THF. 

Table 9.2 Cross-coupling reactions of calcium organocuprate reagents with benzoyl chloride.°...

Likewise, the reaction of iodonium salt 57 with lithium organocuprate reagents affords products of coupling 65 in good yields (Scheme 30) [54]. 

In addition to their reactions with acid chlorides, epoxides, and a,P-unsaturated carbonyl compounds (Sections 20.13-20.15), organocuprate reagents (R2CuLi) also react with organic halides R X to form coupling products R-R that contain a new C-C bond. Only one R group of the organocuprate is transferred to form the product, while the other becomes part of RCu, a reaction by-product. 

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