Bromotrimethylsilane

[2857-97-8] C3H9BrSi (MW 153.09)1 (mild and selective reagent for cleavage of lactones, epoxides, acetals, phosphonate esters and certain ethers; effective reagent for formation of silyl enol ethers; can function as brominating agent) Alternate Name: TMS-Br. Physical Data: bp 79 °C; d 1.188 g cm−3; nD20 1.4240; fp 32 °C. Solubility: sol CCl4, CHCl3, CH2Cl2, ClCH2CH2Cl, MeCN, toluene, hexanes; reactive with THF (ethers), alcohols, and somewhat reactive with EtOAc (esters). Form Supplied in: colorless liquid, packaged in ampules. Analysis of Reagent Purity: well characterized by 1H, 13C, and 29Si NMR spectroscopy. Preparative Methods: although many methods are reported,1 only a few are provided here: Chlorotrimethylsilane undergoes halogen exchange with either Magnesium Bromide2 in Et2O or Sodium Bromide3 in MeCN, which allows in situ reagent formation (eq 1); alternatively, Hexamethyldisilane reacts with Bromine in benzene solution or neat, to afford only TMS-Br with no byproducts (eq 2).4 TMS-Br may also be generated by reaction of hexamethyldisiloxane and Aluminum Bromide (eq 3).5 However, it should be noted that the reactivity of in situ generated reagent appears to depend upon the method of preparation. (1) (2) (3) Purification: by distillation. Handling, Storage, and Precautions: extremely sensitive to light, air, and moisture; fumes in air due to hydrolysis (HBr), and becomes discolored upon prolonged storage (free Br2).