organocopper

Organocopper compounds are organometallic species that contain a carbon–copper bond. The most widely used are organocuprates, such as Gilman reagents of the form R2CuLi, formed by transmetalation of organolithium or Grignard reagents with copper(I) salts (commonly CuI) in ether solvents. In solution these reagents behave as aggregates or contact ion pairs and function as soft carbon nucleophiles with relatively low basicity.

These reagents enable a range of carbon–carbon bond-forming transformations. A hallmark is conjugate (1,4-) addition to enones, producing β-substituted ketones after workup. They also promote allylation of aldehydes to give homoallylic alcohols and participate in various substitution reactions with allyl, benzyl, and vinyl halides, often under milder conditions than organolithium or Grignard reagents. In epoxide opening, organocuprates typically attack the less substituted carbon, yielding alcohols bearing the new substituent.

Preparation and handling considerations are important. Organocopper reagents are generally air- and moisture-sensitive, requiring low temperatures and inert atmosphere. They can be less effective with hindered or certain stubborn electrophiles without modification, and stoichiometric copper and organolithium or Grignard reagents can generate significant waste. Modern copper-catalyzed cross-coupling methods have supplemented or replaced some uses of stoichiometric organocuprates, expanding the toolbox for C–C bond formation.

Overall, organocopper chemistry provides versatile strategies for forming carbon–carbon bonds, with enduring utility in organic synthesis, including complex molecule construction and natural product synthesis.