2-Propenylmagnesium Bromide-Copper(I) Iodide1

(2-propenylmagnesium bromide)

[13291-18-4]  · C3H5BrMg  · 2-Propenylmagnesium Bromide-Copper(I) Iodide  · (MW 145.29) (CuI)

[7681-65-4]  · CuI  · 2-Propenylmagnesium Bromide-Copper(I) Iodide  · (MW 190.45)

(undergoes conjugate addition to cyclohexenone;2 adds regioselectively to b,g-epoxides3)

Preparative Method: prepared in situ under anhydrous conditions by reacting 2-propenylmagnesium bromide (1) with Copper(I) Iodide (2) in varying molar ratios.

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

Conjugate Addition.

Cyclohexenone reacts with (1) in the presence of catalytic (2) to give 3-isopropenylcyclohexanone (3) (eq 1).2 Attempts to access (3) via dehydration of (4) result in mixtures of (3) and the cyclohexenone (5) (eq 2).

Regioselective Opening of b,g-Epoxy Alcohols.

Epoxy alcohol (6) reacts with (1) and catalytic (2) to give 1,3 diol (7) with high regioselectivity for addition at C-2; none of the 1,2-diol resulting from addition to C-3 is observed (eq 3).3 The reaction is dependent upon temperature and solvent. Reactions involving vinylic Grignard reagents give best results when carried out at -20 to -25 °C; THF is an essential cosolvent. Regioselectivity in related epoxy alcohols ranges from 4:1 to 7:1.

1. For a recent review of organocopper reagents, see: Lipshutz, B. H.; Sengupta, S. OR 1992, 41, 135.
2. House, H. O.; Latham, R. A.; Slater, C. D. JOC 1966, 31, 2667.
3. Tius, M. A.; Fauq, A. H. JOC 1983, 48, 4131.

Michael N. Greco

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

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