Trimethyl silane, preparation

TrimcthylsUylmcthylmagncsiiun chloride, (CH3)3SiCH2MgCl (1). Mol. wt. 146.99. The Grignard reagent is prepared in the usual way by reaction of magnesium with chloromethyl(trimethyl)silane.1... 

A number of acyl trimethyl silanes chiral at the a- or -carbon atom have been prepared in non-racemic form. Chiral a-alkoxy and a-silyloxy acyl silanes have been generated in very high yields by oxidative rearrangement of enantiomerically pure silyl epoxides, induced by dimethyl sulphoxide and silyl triflates (Scheme 32)112. 

The reagent can be prepared in high yield by reaction of the Grignard derivative of the inexpensive chloromethyl(trimethyl)silane (Petrach Systems) with paraformaldehyde (ca. 95% yield).1... 

Alkynyl(trimethyl)silanes, germanes, and stannanes produce alkynyl-(phenyl)-A3-iodanes via ligand exchange on iodine under similar conditions [36]. Stang and co-workers developed a useful procedure for the preparation of diverse /3-functionalized alkynyl-A3-iodanes, which involves a ligand exchange of cyano-A3-iodane 19 with alkynylstannanes [37]. 

Dibromomethyl(trimethyl)silane, (CH3)3SiCHBr2 (1). The reagent is prepared from CH2Br2 and (CH3)3SiCl. ... 

Arylacetylenes.3 Arylacetylenes can be prepared simply and in fairiy good yields (30-80%) by reaction of an arylcopper reagent with iodoethynyl(trimethyl)silane at 0° (3 hr.) and then at 20° (6 hr.). The protective trimethylsilyl group can be removed quantitatively by treatment with alkali.4... 

Trimethylsilylmethyl)triphenylarsonium Tetraphenylborate (4) A solution of chloro(trimethyl)silane (4.1 g, 38 mmol) in EtjO (40 mL) was added to a solution of triphenylarsonium methylide, prepared from methyltriphenylarsonium iodide (11.2 g, 25 mmol) and PhLi (25 mmol) in EtjO (230 mL). The mixture was stirred at — 70 °C for 1 h and at 20 °C for 2 h. The white precipitate was filtered off, washed several times with EtjO, dissolved in MeOH (30 mL), and sodium tetraphenylborate (8.5 g, 25 mmol) in MeOH (20 mL) was added. After separation, the crude product was recrystallized (1,2-dichloroethane/EtOAc/ EtjO) yield 12.1 g (68%) mp 174-176°C. 

Several different methods have been employed for the preparation of diazo(trimethylsilyl)meth-ane (1). At present, the best synthetic method seems to be the diazo transfer reaction between diphenylphosphoryl azide and (trimethylsilyl)methylmagnesium chloride.However, the product often contains (chloromethyl)trimethylsilane and hexamethyldisiloxane as impurities. This method can also be employed for the synthesis of diazo(triethylsilyl)methane and diazo(di-ethylmethylsilyl)methane. The diazo transfer reaction can also be carried out with (trimethyl-silyl)methyllithium and tosyl azide. Other methods are the silylation of diazomethane with (trimethylsilyl)trifluoromethanesulfonate or chloro(trimethyl)silane and the base-induced cleavage of A-nitroso-A-[(trimethylsilyl)methyl]urea or the related carbamate or acet-amide.2° =... 

When chloro(trimethyl)silane is added, the five- and six-membered ring acyloins can be prepared, as can also open-chain acyloins from monocarb-oxylic esters 147... 

Alkanoic acids. Monohydroboration of l-alkynyl(trimethyl)silanes (2) with dicyclohexylborane leads to 1-boryl-l-silylalkenes (3) almost exclusively. The usual alkaline peroxide oxidation of 3 gives alkanoic acids (4). Related reactions can be used to prepare a, - and /S,y-unsaturated acids. ... 

Hadjikyriacou et al. utilized the nonhomopolymerizable monomer DPE to prepare a variety of end-functionalized polymers. The reaction of DPE (1.25 molar equivalents) with the quasiliving TiCU-initiated IB polymerization is quantitative and only monoaddition occurs. Subsequent addition of l-methyoxy-2-methyl-l-propenyloxy-trimethyl silane or 1-cyclohexyenyloxy-trimethylsilane to the diarylcarbocation produced the ester- and ketone-fiinctionalized polymers. 

The greater affinity of silicon for hard bases allows the preparation of iodo-ethynyl(trimethyl)silane by the following exchange reaction (54). 

Cunico and Maity published another example of palladium-catalyzed CO-free carbonylation of aryl halides [121]. Depending on the substrate, 2 mol% of either Pd(PPh3)4 or Pd(P Bu3)2 was used to catalyze the reaction of heteroaryl and aryl bromides with A,A -dimethyl-carbamoyl(trimethyl)silane (Scheme 2.10). Tertiary amides were prepared in good yields by direct carbamoylation under their conditions. Remarkably, chlorobenzene, 1-chloro -methoxybenzene, and iodoben-zene gave the desired products in 74, 78, and 60 % yields, respectively. 

Carbonylation. Dialkylchloroboranes have also been used in the preparation of asymmetric ketones via reduction-hydroboration-carbonylaton protocol. In the presence of 1.0 equiv of trimethyl silane, IpcBCl2 is reduced to IpcBHCl, which selectively hydroborates terminal olefins faster than internal olehns, furnishing the dialkyl chloroborane. Upon further reduction of the R2BCI with LiAlH4, the internal olefin undergoes hydrobora-... 

Preparative Methods (2-phenylsulfonylethyl)trimethylsilane (2) is prepared by radical addition of thiophenol to vinyltrimethylsilane to give (2-phenylthioethyl)trimethyl-silane (1), which is then oxidized with hydrogen peroxide (eq 1).2 3... 

Alternative Routes to Substituted (2-Phenylsulfonylethyl)-trimethylsilanes. Although the fluoride-induced elimination is a reliable and efficient method for synthesizing alkenes, the requisite silyl sulfone precursors are often better prepared by methods which avoid the use of (2). For example, eq 3 illustrates an alternative synthesis of 2,2-dialkyl-2-(phenylsulfonylethyl)trimethyl-silanes involving alkylation of a lithio sulfone with (iodomethyl)-trimethylsilane. ... 

Methyl enol ethers of acyl silanes have been prepared in good yield by the silyla-tion of vinyl lithium reagents derived from methyl enol ethras . Indeed, po-haps the simplest preparation of a methyl enol ether of an acyl silane results from addition of a-methoxyvinyl lithium to chlorotrimethylsilane. Acid hydrolysis gave acetyl trimethyl-silane in ca 80% yield . A similar reaction has been carried out with phenyl methyl (-butyl chlorosilane. Again, acid hydrolysis gave the acyl silane, which is of course chiral at silicon . ... 

Preparative Methods [difluoro(phenylthio)methyl]trimethyl-silane (PhSCF2SiMe3) was prepared for the first time by Prakash et al., using the Barbier coupling reaction of bromodi-fluoromethylphenyl sulfide, prepared from dibromodifiuoro-methane and sodium benzenethiolate, magnesium metal, and chlorotrimethylsilane (TMSCl) in DMF (eq 1). 

Reactions at acid centers to create 5 -2-(trimethylsilyl) ethanethiolesters are also common. Carboxylic 5-thiolesters are formed in high yield by the DCC/DMAP mediated coupling of 2-(trimethylsilyl)ethanethiol and carboxylic acids or by thiol substitution on a carboxylic acid chloride. 5 -2-(Tiimethylsilyl) ethyl p-toluenethiolsulfonate is formed by treating 2-(trimethyl-silyl)ethanethiol with tosyl bromide (eq 4). The product is a useful electrophile for carbon nucleophiles, allowing the introduction of the 2-(trimethylsilyl)ethylthio unit by an alternative mechanism. Independent of the thiol, aryl and alkyl 2-trimethylsilylethyl thioethers may be prepared by the radical addition of the appropriate arene- or aikanethiol to vinyl trimethyl-silane in a reaction comparable to that of eq l7 ... 

Preparative Method prepared in situ under an inert atmosphere hy hthium-halogen exchange of (l-bromovinyl)trimethyl-silane with r-hutyllithium. 

Trimethyl(l-phenyl-2-propenyl)silane of high enantiomeric excess has also been prepared by asymmetric cross coupling, and reacts with aldehydes to give optically active products in the presence of titanium(IV) chloride. The stereoselectivity of these reactions is consistent with the antiperiplanar process previously outlined75. 

Trimethvl Vinvlbenzvl Stannane—This procedure is identical to the preparation of trimethyl vinylbenzyl silane with the substitution of trimethyl tin chloride for the chlorotrimethyl silane. The following quantities were used 32.6 g (0.2136 mol) vinylbenzyl chloride in 65 mL of ether, 7.81 g (0.3211 mol) magnesium turnings. 

Copolymers having enhanced oxygen permeability and water transport properties consisting of 3-methacryloxypropyltris(trimethyl-siloxy)silane, (V), and 2-methacryloyloxymethyl-18-crown-6, (VI), were prepared by Salamone et al. (6) and used as contact lenses. 

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