Mesitylcopper(I)

[75732-01-3]  · C9H11Cu  · Mesitylcopper(I)  · (MW 182.75)

(thermally stable and soluble metalation agent for active hydrogen compounds;1 nontransferable group of mixed organocuprates;1 catalyst for conjugate reduction of a,b-unsaturated carbonyl compounds by lithium aluminum hydride1)

Alternate Name: 2,4,6-trimethylphenylcopper(I).

Physical Data: thermally stable up to ca. 100 °C; exists as a pentamer.

Solubility: sol benzene, ether, THF; partly sol hexane.

Preparative Method: prepared by the metathesis reaction between Copper(I) Chloride and mesitylmagnesium bromide in THF and can be isolated by precipitating magnesium salts with addition of dioxane.1

Handling, Storage, and Precautions: extremely oxygen- and moisture-sensitive. Preparation and reaction should be conducted under rigorously oxygen-free and anhydrous conditions.

Metalation.

Copper(I) t-Butoxide has been known to be a useful metalation agent for a variety of active hydrogen compounds under mild conditions with concomitant quantitative liberation of t-butyl alcohol to generate corresponding organic CuI compounds. Mesitylcopper(I) is a unique organocopper(I) compound with high thermal stability and solubility, and acts as a more powerful metalation agent than copper(I) t-butoxide with concomitant liberation of inert mesitylene and without accompanying salts. For example, mesitylcopper(I) effects the metalation of primary and secondary amines (eq 1),1,2 which copper(I) t-butoxide cannot perform. Metalation of functionalized benzoic acids3 such as 2-bromobenzoic acid (eq 2) occurs readily, where mesitylcopper(I) is more efficient than 2-tolylcopper(I). Copper(I) 2-bromobenzoate is an intermediate of the Hurtley reaction and cannot be prepared by the conventional Copper(I) Oxide method. Metalation of perfluoro-t-butyl alcohol affords copper(I) perfluoro-t-butoxide (eq 3),4 which is one of the most volatile copper alkoxides and may be useful for sol-gel and chemical vapor deposition processes. Organic reactions utilizing the excellent thermal stability of mesitylcopper(I) have been reported: formaldehyde insertion into its Cu-C bond5 and its palladium(0)-catalyzed cross-coupling6 with aryl iodides in the presence of Bu4NX (X = Br, I).

Nontransferable Group of Mixed Organocuprates.

Nontransferable groups of mixed organocuprates have been developed for stabilizing organocuprate reagents and for saving one organic group of diorganocuprates. Mesitylcopper(I) can be used for a nontransferable group of mixed organocuprates having primary and secondary alkyl groups (eq 4).1

Catalyst for Conjugate Reduction of a,b-Unsaturated Carbonyl Compounds by Lithium Aluminum Hydride.

Mesitylcopper(I) catalyzes conjugate reduction of a,b-unsaturated aldehydes and ketones by Lithium Aluminum Hydride (LAH) in the presence of Hexamethylphosphoric Triamide (HMPA) (eq 5).1 Mesitylcopper(I)/LAH/HMPA has been the basis of the development of the related reagents CuI/LAH/HMPA7 and MeCuI/DIBAL/HMPA,8 which similarly effect conjugate reduction of a,b-unsaturated carbonyl compounds (see Lithium Aluminum Hydride-Copper(I) Iodide, Methylcopper, and Diisobutylaluminum Hydride).


1. Tsuda, T.; Yazawa, T.; Watanabe, K.; Fujii, T.; Saegusa, T. JOC 1981, 46, 192.
2. Tsuda, T.; Watanabe, K.; Miyata, K.; Yamamoto, H.; Saegusa, T. IC 1981, 20, 2728.
3. Aalten, H. L.; van Koten, G.; Goubitz, K.; Stam, C. H. OM 1989, 8, 2293.
4. Purdy, A. P.; George, C. F. IC 1991, 30, 1969.
5. Leoni, P.; Pasquali, M. T. JOM 1983, 255, C31.
6. Bumagin, N. A.; Kalinovskii, I. O.; Beletskaya, I. P. JOM 1984, 267, C1.
7. Tsuda, T.; Fujii, T.; Kawasaki, K.; Saegusa, T. CC 1980, 1013.
8. (a) Tsuda, T.; Hayashi, T.; Satomi, H.; Kawamoto, T.; Saegusa, T. JOC 1986, 51, 537. (b) Tsuda, T.; Satomi, H.; Hayashi, T.; Saegusa, T. JOC 1987, 52, 439.

Tetsuo Tsuda

Kyoto University, Japan



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