Halides organocuprates

The alkyl or aryl halide -organocuprate coupling disconnection is... 

Organocuprates can be prepared from organolithium reagents and cuprous halides. Organocuprates react with alkyl halides to form a new C-C bond in the product 24,25, 32, 33, 42. 

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... 

Reaction of Alkyl Halides and Sulfonate Esters With Organocuprates... 

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... 

Similarly to the alkyl derivatives, the most common route for arylcopper compounds is the reaction of a copper halide and aryllithium compounds (Equation (4)). Organocuprates with aryl groups are obtained by using an appropriate excess of the lithium reagent. Magnesium aryls have also been employed in transmetallation reactions with Cu(l) salts to yield both arylcopper compounds and arylcuprates (Equations (5) and (6)). 

Reactions with cyclopropene.11 Lithium organocuprates react with the cyclo-propenone ketal 1 (12, 152-154) to form a copper species (a) that behaves as an enolate of a cyclopropanone. Thus it reacts with alkyl halides to form cis-2,3-disubstituted derivatives of 1. 

Addition of RJCuLi to bridgehead enones.1 Ordinarily organocuprates do not react with a bridgehead halide. However, they can undergo conjugate addition to bridgehead enones generated in situ from p-bromo ketones with potassium t-butoxide or lithium 2,6-di-r-butyl-4-methylphenoxide (6,95). 

Organocuprates react rapidly with allylic halides (or acetates), propargyl halides (or acetates), and vinyloxiranes, frequently with 5 2 regioselectivity. The reaction ordinarily takes place with anti (with respect to the leaving group) stereochemistry. 

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). 

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