Bromotrimethylsilane

Bromotrimethylsilane can protect or deprotect functional groups selectively, act as silane blocking agent, which is widely used in the syntheses of drugs.

Clear yellow liquid

bp 79°C; d 1.188 g cm?3; n20 D 1.4240; fp 32°C.

Bromotrimethylsilane is a 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.
Amines react with TMS-Br to form isolable adducts, which react readily with ketones to form enamines under mild conditions (eq 15).

Powerful silylating agent

Adefovir intermediate

although many methods are reported, only a few are provided here: chlorotrimethylsilane undergoes halogen exchange with either magnesium bromide in Et2O or sodium bromide 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).However, it should be noted that the reactivity of in situ generated reagent appears to depend upon the method of preparation.

Bromotrimethylsilane is used with Cl₃ to catalyze the direct allylation of a variety of alcohols with allyltrimethylsilane.

Purify it by repeated fractional distillation and store it in sealed ampoules in the dark. [McCusker & Reilly J Am Chem Soc 75 1583 1953.] Also fractionate it through a 15-plate column (0.8 x 32cm packed with 1/16in single turn helices of Pt-Ir wire). [Gilliam et al. J Am Chem Soc 68 1161 1946, Pray et al. J Am Chem Soc 70 433 1948, Beilstein 4 IV 4008.]