Question

How many types of reaction are given by organanocopper reagents?

Answer 1

Reactions of organocopper reagents involve species containing copper-carbon bonds acting as nucleophiles in the presence of organic electrophiles. Organocopper reagents are now commonly used in organic synthesisas mild, selective nucleophiles for substitution and conjugate addition reactions.[1]

Since the discovery that copper(I) halidescatalyze the conjugate addition of Grignard reagents in 1941,[2] organocopper reagents have emerged as weakly basic, nucleophilic reagents for substitution and addition reactions. The constitution of organocopper compounds depends on their method of preparation and the various kinds of organocopper reagents exhibit different reactivity profiles. As a result, the scope of reactions involving organocopper reagents is extremely broad.

Organocopper complexes (RCu) are produced when a copper(I) halide and organolithium are combined. In conjunction with Lewis acidic additives such as boron trifluoride etherate, these reagents are used for conjugate addition reactions.[3]

Lower-order cuprates (R2CuLi, also known as Gilman reagents) result when organocopper complexes are treated with an equivalent of organolithium. Alternatively, they may be formed by the treatment of a copper(I) halide with two equivalents of organolithium. They undergo substitution, conjugate addition, and carbocupration reactions in the presence of the appropriate organic substrates.[4] Mixed Gilman reagents consist of two different R groups, one of which is typically a non-transferrable "dummy" group.

Lower-order cyanocuprates (RCu(CN)Li) are similarly derived from an organolithium compound and copper(I) cyanide; however, intermediate organocopper complexes do not form during this reaction and thus only a single equivalent of organolithium reagent is necessary.[1] Cyanocuprates undergo SN2' substitution in the presence of allyl electrophiles and conjugate addition reactions in the presence of enones.

Higher-order cyanocuprates (R2Cu(CN)Li2) are formed upon the reaction of two equivalents of organolithium with copper(I) cyanide. These reagents are more reactive towards substitution than the corresponding lower-order cyanocuprates.[5]