Ethers bromotrimethylsilane

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. 

Formation of Enol Ethers. Bromotrimethylsilane with tri-ethylamine in DMF is an effective medium for production of thermodynamic (Z) silyl enol ethers (eq 11). 

The completion of the synthesis of gilvocarcin V (2) only requires a few functional group manipulations. Hydrogenolysis of the four benzyl groups, followed by acetylation of the liberated hydroxyl groups, provides 30 in 68 % overall yield. After cleavage of the MOM ether in 30 with bromotrimethylsilane, application... 

Bromotrimethylsilane has proven to be useful for a wide variety of applications most of them being reviewed.5 8 Other recent applications are mild cleavage of oxiranes,9 the synthesis of glycosyl bromides,10 the selective cleavage of tetrahydro-2,5-dimethoxyfuran and tetrahydro-2,6-dimethoxy-pyran,11 the cleavage of esters and ethers,12 and the synthesis of benzyl bromides.13... 

Bromotrimethylsilane reacts with lactones884, with cyclic ethers, particularly oxiranes, and with secondary and tertiary ethers885 to yield brominated products. The reaction is catalyzed by IBr (equation 128)886. 

The simultaneous and selective protection of the two equatorial hydroxyl groups in methyl dihydroquinate [11L1, Scheme 3.111 j as the butane-2,3-diace-tal 111 2 was a key strategic feature in a synthesis of inhibitors of 3-dehydroqui-nate synthase.205 Later in the synthesis, deprotection of intermediate 111.4 required three steps (a) hydrolysis of the trimethylsilyl ether and the butane-2,3-diacetal with trifluoroacetic acid (b) cleavage of the isopropyl phosphonate with bromotrimethylsilane and (c) hydrolysis of the methyl ester with aqueous sodium hydroxide. Compound 111 1 has also been used in the synthesis of inhibitors 3-dehydroquinate dehydratase206 and influenza neuraminadase207-208 as well as shikimic add derivatives.209 210... 

Cleavage of lactones and carbonates. Lactones and carbonates react with bromotrimethylsilane to afford bromocarboxylic acid derivatives (equation I) and bromohydrin trimethylsilyl ethers (equation II), respectively acyclic, aliphatic esters do not react with bromotrimethylsilane. lodotrimethylsilane reacts in an analogous fashion with lactones, but in reaction with ethylene carbonate the main product is 1,2-diiodoethane (equation III). The >-bromocarboxylate derivatives are converted into acid chlorides by reaction with SOCL (equation I). 

Alkyl bromides. Alcohols are converted into bromides by reaction with bromotrimethylsilane (1.5-4 equiv.) in CHCI3 at 25-50° (equation I). The reaction occurs with inversion. Tertiary and benzylic alcohols react more rapidly than primary or secondary alcohols. Bromides are not formed under the same conditions from Irimethylsilyl ethers of alcohols. However, trimethyl orthoformate is converted into methyl formate, HC(OCH3)3 —s HCOOCH3. Unlike iodotrimethylsUane, the bromosilane does not dealkylate esters, ethers, or carbamates. 

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]. ... 

He et al. have prepared phosphonated aiyl trifluorovinyl ethers containing flexible oligo(ethylene oxide) units and subsequently homopolymerized these monomers by thermal cyclopolymerization in bulk at 180 °C. The resulting polymer was treated with bromotrimethylsilane to obtain the phosphonic acid derivative. The phosphonated trifluorovinyl ether monomers were also copolymerized with tetrafluoroethylene via free radical pol3Tnerization in an autoclave at 70 °C using l,l,2-trichloro-l,2,2-tri-fluoroethane as solvent. Moreover, radical terpolymerizations of the same trifluorovinyl ether monomers were performed with mixtures of... 

Bromotrimethylsilane, a reagent similar to but not as powerful as lodotrimethylsilane, will cleave MOM ethers as well as acetonide, THP, trityl, and f-BuMe2Si groups, but the reagent will not cleave esters, methyl and benzyl ethers, f-butyl-diphenylsilyl ethers, and amides. One example is shown in eq 6. ... 

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