Acetals bromotrimethylsilane

Glycosyl bromides.1 Glycosyl bromides can be prepared conveniently and in High yield by reaction of bromotrimethylsilane with anomcric glycosyl acetates. Ulter groups at other positions are stable under the mild conditions (25°, HCC13, 4II min) employed. Methyl glycosides can also be used, but 1,2-O-isopropylidenes rend very slowly. 

Ethers Aluminum chloride-Sodium iodide. Aluminum iodide. Bis(isopropylthio)boron hromide. Boron trichloride. Boron trifluoride etherate. Bromotrimethylsilane. 2-Chloro-1,3,2-dithioborolane. Chlorotri-methylsilane-Acetic anhydride. Chlorotri-methylsilane-Sodium iodide. Dimethyl-boron bromide. Pyridinium p-toluenesulfo-nate. Sodium methaneselenolate. 

The trimethylsilylation of relatively unreactive hydroxy- and oxo-steroids with hexamethyldisilazane, for gas chromatographic-mass spectrometric analysis, is catalysed by the addition of bromotrimethylsilane. Oxo-steroids readily afford trimethylsilyl enol ethers. Relative retention times (g.l.c.) have been obtained for about 90 sterols and their acetates, on a variety of columns. ... 

Halosilanes are very effective at cleaving MOM ethers in the presence of a range of polar functional groups. Thus, bromotrimethylsilane removes MOM ethers at -30 C in dichloromethane - — conditions that preserve TBDPS ethers, but TBS ethers may cleave to some extent whereas trityl ethers, tetrahy-dropyranyl ethers, and isopropylidene acetals seldom emerge unscathed. The method has been employed in syntheses of Nogalamycm" and Gilvocarcin without detriment to two phenolic methyl ethers, a lactone and four acetate esters [Scheme 4.243]. ... 

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