Gilman reagent

A Gilman reagent is a lithium and copper (diorganocopper) reagent compound, R₂CuLi, where R is an alkyl or aryl. These reagents are useful because, unlike related Grignard reagents and organolithium reagents, they react with organic halides to replace the halide group with an R group (the Corey-House reaction). Such displacement reactions allow for the synthesis of complex products from simple building blocks.

These reagents were discovered by Henry Gilman and coworkers.Lithium dimethylcopper (CH₃)₂CuLi can be prepared by adding copper(I) iodide to methyllithium in tetrahydrofuran at −78 °C. In the reaction depicted below, the Gilman reagent is a methylating reagent reacting with an alkyne in a conjugate addition, and the negative charge is trapped in a nucleophilic acyl substitution with the ester group forming a cyclic enone.

Lithium dimethylcuprate exists as a dimer in diethyl ether forming an 8-membered ring. Similarly, lithium diphenylcuprate crystallizes as a dimeric etherate, [{Li(OEt₂)}(CuPh₂)]₂.

If the Li⁺ ions is complexed with the crown ether 12-crown-4, the resulting diorganylcuprate anions adopt a linear coordination geometry at copper.

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