Gilman Reagent

What are Gilman Reagents?

A Gilman Reagent is an organometallic reagent containing two R-groups (alkyl or aryl), copper, and lithium. The general formula of Gilman reagents can be expressed as R2CuLi. Unlike Grignard reagents, these compounds tend to replace the halide group with an R group when reacted with organic halides. Therefore, Gilman reagents have crucial applications in the Corey-House reaction. Furthermore, relatively complex products can be synthesized from simple blocks via displacement reactions involving the Gilman reagent.

Gilman reagents were discovered by (and are named after) the American organic chemist Henry Gilman. The most common example of a Gilman reagent is lithium dimethylcuprate. When dissolved in diethyl ether, this compound exists as a dimer by forming an 8-membered ring with another lithium dimethylcuprate molecule.

Preparation

Lithium dimethylcopper can be prepared by reacting methyllithium (one of the simplest organolithium reagents with the chemical formula CH3Li) with copper (I) iodide (also known as cuprous iodide, has a chemical formula of CuI) in a reaction environment provided by tetrahydrofuran. The optimum reaction temperature for the preparation of this compound is approximately -78 degrees Celsius.

Reactions Undergone by Gilman Reagents

Gilman reagents act as methylating agents when subjected to conjugate addition reactions with alkynes. The negative charge on the reagent becomes trapped with the ester group via a nucleophilic acyl substitution reaction, resulting in the formation of a cyclic enone. On conjugated enones, these compounds tend to perform 1,4 additions rather than 1,2 additions.

Applications of Gilman Reagents

Some important applications of Gilman reagents are provided below.

  • Gilman reagents can be employed to perform conjugate additions on alpha, beta-unsaturated ketones. Grignard reagents are not viable here since they tend to add to the carbonyl carbon.
  • Gilman reagents also prove to be highly effective nucleophile in SN2 reactions.

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Frequently Asked Questions – FAQs

What is a Gilman Reagent?

A Gilman Reagent is an organometallic reagent containing two R-groups (alkyl or aryl), copper, and lithium. The general formula of Gilman reagents can be expressed as R2CuLi. Unlike Grignard reagents, these compounds tend to replace the halide group with an R group when reacted with organic halides.

Who discovered Gilman Reagents?

Gilman reagents were discovered by (and are named after) the American organic chemist Henry Gilman. The most common example of a Gilman reagent is lithium dimethylcuprate. When dissolved in diethyl ether, this compound exists as a dimer by forming an 8-membered ring with another lithium dimethylcuprate molecule.

How can Gilman Reagents be Prepared?

Lithium dimethylcopper can be prepared by reacting methyllithium (one of the simplest organolithium reagents with the chemical formula CH3Li) with copper (I) iodide (also known as cuprous iodide, has a chemical formula of CuI) in a reaction environment provided by tetrahydrofuran.

What is the optimum temperature for the preparation of Gilman reagents?

The optimum reaction temperature for the preparation of this compound is approximately -78 degrees Celsius.

What are the applications of Gilman reagents?

Gilman reagents can be employed to perform conjugate additions on alpha, beta-unsaturated ketones. Grignard reagents are not viable here since they tend to add to the carbonyl carbon. Gilman reagents also prove to be highly effective nucleophile in SN2 reactions.

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