2-(3-Trimethylsilyl-1-propenyl)magnesium Bromide-Copper(I) Iodide1

[103559-91-7]  · C6H13BrMgSi  · 2-(3-Trimethylsilyl-1-propenyl)magnesium Bromide-Copper(I) Iodide  · (MW 217.49)

[7681-65-4]  · CuI  · 2-(3-Trimethylsilyl-1-propenyl)magnesium Bromide-Copper(I) Iodide  · (MW 190.45)

(used in methylenecyclopentane annulation via conjugate addition to enones;2b can serve as hydroxymethylvinyl anion equivalent3)

Preparative Methods: copper(I) iodide-catalyzed reactions of 2-(3-trimethylsilyl-1-propenyl)magnesium bromide (1) have been carried out in ether or THF by combining (1) with a catalytic amount of Copper(I) Iodide at -30 to 0 °C. Two different preparations of (1) have been reported.2a,3

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

Methylenecyclopentane Annulation.

Trost and Coppola2b applied the copper(I) iodide-catalyzed addition of (1) to enones; the conjugate adducts were converted to the corresponding methylenecyclopentanes in good yield (eqs 1-3). Attempts to generate stoichiometric cuprates were complicated by oxidative dimerization.

1-Hydroxymethylvinyl Anion Equivalent.

Copper(I) iodide-catalyzed addition of (1) to epoxides affords allylsilanes (2) (eq 4).3 Oxidation of (2) to the corresponding allylic alcohols (3) constitutes formal addition of a hydroxymethylvinyl anion to an epoxide (eq 5). Alcohols (3) were converted to the corresponding a-methylene-g-lactones (4) upon further oxidation (eq 6).

Related Reagents.

2-Bromo-3-trimethylsilyl-1-propene; Isopropenylmagnesium Bromide; 2-Propenylmagnesium Bromide-Copper(I) Iodide; 1-(Trimethylsilyl)vinylmagnesium Bromide-Copper(I) Iodide.

1. For a recent review of organocopper reagents, see: Lipshutz, B. H.; Sengupta, S. OR 1992, 41, 135.
2. (a) Trost, B. M.; Chan, D. M. T. JACS 1982, 104, 3733. (b) Trost, B. M.; Coppola, B. P. JACS 1982, 104, 6879.
3. Nishiyama, H.; Yokoyama, H.; Narimatsu, S.; Itoh, K. TL 1982, 1267.

Michael N. Greco

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

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