(2-Bromoallyl)trimethylsilane

Physical properties

bp 46–50°C/20 mmHg,64–65°C/38– 39 mmHg.

The Uses of (2-Bromoallyl)trimethylsilane

2-Bromo-3-trimethylsilyl-1-propene can be used as synthon for CH2=C?CH2TMS1–3 and CH2=CBrC?H2;2 for synthesis of 1-trimethylsilylmethyl-substituted 1,3-butadienes.
The 1-trimethylsilylmethylvinyl anion CH2=C(M)CH2TMS (2) (M = Li, Mg, Cu, etc.), readily prepared from 2-bromo-3-trimethylsilyl-1-propene (1) under typical conditions, allows the introduction of the synthetically useful 1-trimethylsilylmethylvinyl group to a wide variety of substrates. Ring opening of 1-butene oxide with the Grignard reagent (2) (M = MgBr) in the presence of copper(I) iodide gives only one regioisomer. Subsequent desilylative oxidation of this allyl alcohol to α-methylene-γ-lactones provides further utility of (1) as a 1-hydroxymethylvinyl anion equivalent, i.e. CH2=?C?CH2OH (eq 1).Alternatively, the alcohol from trans-2,3-epoxybutane provides a route to the unstable sixmembered β,γ-unsaturated lactone (eq 2).The copper-catalyzed 1,4-addition to the typically unreactive mesityl oxide proceeds smoothly. The versatility of the allylsilane moiety is again illustrated in the ethylaluminum dichloride-induced cyclization of the adduct to a tertiary cyclopentanol in high yield (eq 3).

Preparation

reaction of 2,3-dibromopropene with lithium (trimethylsilyl)cuprate in HMPA at 0°C (63–90%);(2) reaction of 2,3-dibromopropene with trichlorosilane in the presence of trichlorosilane and copper( I) chloride, followed by treatment with methylmagnesium bromide (63–71%).

Purification Methods

It is fractionally distilled through an efficient column. It is flammable. [Trost & Chan J Am Chem Soc 104 3733 1982, Trost & Coppola J Am Chem Soc 104 6879 1982.]