Vinylmagnesium Bromide-Copper(I) Iodide1


[1826-67-1]  · C2H3BrMg  · Vinylmagnesium Bromide-Copper(I) Iodide  · (MW 131.26) (CuI)

[7681-65-4]  · CuI  · Vinylmagnesium Bromide-Copper(I) Iodide  · (MW 190.45)

(reaction with epoxides to give optically active allylic alcohols and homoallylic epoxides;2 ring opening of o-alkenyl lactones;3 stereoselective Michael addition to substituted cyclohexenone4)

Preparative Method: vinylmagnesium bromide-copper(I) iodide complexes are prepared in situ under anhydrous conditions by reacting Vinylmagnesium Bromide (1) with Copper(I) Iodide (2) in various molar ratios.

Handling, Storage, and Precautions: use in a fume hood.

Synthesis of Optically Active Allylic Alcohols and Homoallylic Epoxides.

Treatment of epoxy halides (3) with a preformed mixture of (1) and (2) (2 equiv of each) results in the formation of allylic alcohols (4) (eq 1).2 Homoallylic epoxides (5) are formed by addition of (1) (2 equiv) to a mixture of (2) (0.1 equiv), (3) and HMPA (4 equiv) (eq 2).

Regio- and Stereoselective Ring Opening of o-Alkenyl Lactones.

Lactones (6) undergo regioselective ring opening when treated with (1) and catalytic (2) in THF-Me2S to afford alkenoic acids (7) in moderate yield (eq 3).3

Stereoselective Michael Addition.

The enone (8) reacts stereoselectively with a 1:1 mixture of (1) and (2) to give the a-addition product (9) (eq 4).4 Conversely, addition of cyanide to (8) gives the b-addition product.

1. For a recent review of organocopper reagents, see: Lipshutz, B. H.; Sengupta, S. OR 1992, 41, 135.
2. Nicolaou, K. C.; Duggan, M. E.; Ladduwahetty, T. TL 1984, 25, 2069. See: Tius, M. A.; Fauq, A. H. JOC 1983, 48, 4131, for the reaction of (1) and (2) with b,g-epoxy alcohols.
3. Kawashima, M.; Sato, T.; Fujisawa, T. BCJ 1988, 61, 3255. Vinylic oxetanes undergo ring opening to homoallylic alcohols: Larock, R. C.; Stolz-Dunn, S. K. SL 1990, 341.
4. Watanabe, M.; Yoshikoshi, A. JCS(P1) 1990, 257.

Michael N. Greco

The R. W. Johnson Pharmaceutical Research Institute, Spring House, PA, USA

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