Vinylmagnesium Bromide-Methylcopper

(CH2=CHMgBr)

[1826-67-1]  · C2H3BrMg  · Vinylmagnesium Bromide-Methylcopper  · (MW 131.26) (MeCu)

[1184-53-8]  · CH3Cu  · Vinylmagnesium Bromide-Methylcopper  · (MW 78.59)

(vinyl group transfer reagent in 1,4-addition reactions with a,b-unsaturated ketones; can reductively remove a g-alkoxy group from a,b-unsaturated ketones)

Solubility: sol ether, THF.

Preparative Methods: generated1,2 in situ from preformed Methylcopper3 and a commercial 1.0 M solution of Vinylmagnesium Bromide in THF. A mixture of purified1,4 copper(I) iodide (n mmol) and THF (4n mL) is treated with a solution of methyllithium (n mmol) in ether at -78 °C. The suspension is warmed to 23 °C, stirred for 15 min, and then cooled to -78 °C and treated with the solution of vinylmagnesium bromide (1n-3n mmol).

Handling, Storage, and Precautions: must be generated in the absence of moisture and oxygen. It cannot be stored. Use in a fume hood.

Introduction.

The reagent is believed to consist of mixed magnesium homocuprates, (CH2=CH)nMeCu(MgBr)n (n = 1, 2, or 3), with the formula reflecting mainly the ratio of MeCu to CH2=CHMgBr rather than the structure of the organocopper(I) ate complexes.2,5 The magnesium cuprates are a useful alternative to Lithium Divinylcuprate,3 since the Vinyllithium required for the generation of (CH2=CH)2CuLi is no longer available commercially.

Vinyl Group Transfer.

The selective transfer of the vinyl group in the 1,4-addition of higher order magnesium cuprates, derived from MeCu and CH2=CHMgBr, to an enone is illustrated in eq 1.2 There is almost no 1,2-addition. Conjugate addition products can be prepared in high yields from sterically hindered ketones (eqs 2 and 3).1

Reductive removal of the alkoxy group from a g-alkoxy enone has been observed with the reagent derived from MeCu and CH2=CHMgBr.1 This problem can be overcome by the use of a divinylmagnesium cuprate6 generated from vinylmagnesium bromide and Copper(I) Iodide (eq 4).

Related Reagents.

n-Butylmagnesium Bromide-Methylcopper(I); Vinylmagnesium Bromide-Copper(I) Iodide; Vinylmagnesium Chloride-Copper(I) Chloride.


1. Harding, K. E.; Clement, B. A.; Moreno, L.; Peter-Katalinic, J. JOC 1981, 46, 940.
2. Drouin, J.; Leyendecker, F.; Conia, J.-M. NJC 1978, 2, 267.
3. Lipshutz, B. H.; Sengupta, S. OR 1992, 41, 135.
4. Keller, R. N.; Wycoff, H. D. Inorg. Synth. 1946, 2, 1.
5. Sjoholm, R.; Backlund, P. Finn. Chem. Lett. 1980, 28.
6. Wege, P. M.; Clark, R. D.; Heathcock, C. H. JOC 1976, 41, 3144.

Lucjan Strekowski & Yuri V. Gulevich

Georgia State University, Atlanta, GA, USA



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