Trialkylsilanes preparation

Trialkylsilanes are usually formed by the addition of a lithium or Grignard reagent to the silyl chloride, and thus, discussions related to the formation of the silyl acetylene bond will be kept to a minimum. Silyl acetylenes are prepared from the alkynylcopper(I) reagents in the presence of PPh3, Zn or TMEDA in CH3CN at 100°, 36-98% yield. It is interesting to note that the... 

Ethers have also been prepared by the reductive dimerization of two molecules of an aldehyde or ketone (e.g., cyclohexanone dicyclohexyl ether). This was accomplished by treatment of the substrate with a trialkylsilane and a catalyst. ... 

Lithium aluminum hydride and alanes are frequently used for the preparation of hydrides of other metals. Diethylmagnesium is converted to magnesium hydride [777], trialkylchlorosilanes are transformed to trialkylsilanes... 

The uncalcined and unmodified sample is denoted as MCM-U. This uncalcined sample, i.e., sample with template molecules inside mesopores, was functionalized via one-step process that includes simultaneous trialkylsilanization and extraction of the template. Two modified samples were prepared with trimethylsilyl and octyldimethylsilyl groups attached to the mesopore walls and denoted as MCM-UM and MCM-UO, respectively. A typical synthesis [17] was carried out as follows about 0.2 g of the uncalcined MCM-41 was dispersed in 10 ml of trialkylchlorosilane, and refluxed for 36 hours (modification scheme is shown on Figure 1). Subsequently, about 5 ml of anhydrous pyridine was added to the mixture and refluxed for next 18 hours. After cooling down, the mixture was filtered and washed several times with small portions of ethyl alcohol, mixture of ethyl alcohol and... 

Trifluoromethyl)tributyl tin, prepared from (trifluoromethyl)trimethylsilane and bis(tributyltin) oxide, has been reported81 to react with disilyl sulphides to give the corresponding (trifluoromethyl)di- and (trifluoromethyl)trialkylsilanes. 

Anodic methoxylation of cyclohexyl isocyanide yields a mixture of six products whose formation is thought to be initiated by methoxy radicals 194). Cholesteryl acetate dibromide has been specifically hydroxylated at C25 in 85 to 93% yield at a lead dioxide anode 19 s. Silyl ethers have been prepared in 60 to 95 % yield by electrolysis of trialkylsilanes at a platinum electrode in ROH- Me4NI,... 

There have been several reports of catalytic methods for alcoholysis of trialkylsilanes,10-17 however only a few of these papers have included reactions with dialkyl(dihydrido)silanes.9a,d 15 Among the more reactive catalysts for the preparation of trialkylsilyl ethers from silyl hydrides... 

The direct synthesis of (a-hydroxyalkyl)trialkylsilane by a nucleophilic addition of a trialkylsilyl anion to an aldehyde or a ketone has not been readily accomplished because of the difficulty in the preparation of trialkylsilyl anions. Tin-mediated reverse Brook... 

Odorless borane-sulfide complexes 36a-e65-68 and borane-amine complexes 37a-g69-75 have been recently prepared because of the growing importance of diborane for the synthesis of pharmaceuticals or other compounds and certain inconveniences of well-established reagents, for example, the low concentration and instability of BH3-THF and high volatility, flammability, and unpleasant odor of dimethyl sulfide from BH3-SMe2. Trialkylsilanes, for example, Me3SiH, were found to be an efficient reducing reagent for the in situ preparation of... 

Trimethy (trifluoromethyl)si ane can be converted into tributyl(trifluoromethyl)tin (40) in quantitative yield by treatment with bis(tributyltin) oxide in tetrahydrofuran under fluoride ion initiation.129 Tributyl(trifluoromethyl)tin readily trifluoromethylates disilyl sulfides at room temperature giving the corresponding trifluoromethylated di- and trialkylsilanes 41 in high yields. This method provides a new approach for the preparation of silicon-based trifluoro-methylating reagents via transtrifluoromethylation of compounds containing Si — S bonds. 

The reduction of alcohols with a trialkylsilane in the presence of a protic acid can be complicated by skeletal rearrangement and alkene formation as a result of carbonium ion formation. This problem is significantly reduced when using BF3 as the acid (Eq. 85) [140]. Peptide isosteres (Eq. 86) can be prepared by the alkylative ehmina-tion of y-oxygenated-a,y3-unsaturated carboxylates by use of BF3 complexes of alkyl-copper reagents [141]. 

Protodesilylation of allyl- or aryl-substituted trialkylsilanes with an acid partner is a cleaner method, producing propene or an aromatic hydrocarbon as a volatile inert byproduct. Although some methods of isolation have been reported, they can usually be prepared in situ in aprotic media and employed without further purification. Methods of preparation of representative organosilicon Lewis acids, la, trimethylsilyl bis(trifluoro-methanesulfone)imide (7) [9], trimethylsilyl perchlorate (6a) [10], iodotrimethylsilane, and trimethylsilyl tetrakis(trifluoromethanesulfonyl)borate [11] are described below. In principle, these analogs are also accessible in a similar manner (Table 1) [2d]. 

Although trialkylsilanes are obtained by the lithium aluminum hydride-reduction of trialkylhalosilanes, they are conveniently prepared by the alkylation of trichlorosilane with Grignard reagents (eq (63)) [58]. 

The reduction of a,p-unsaturated aldehydes or ketones with trialkylsilanes has proved a valuable reaction for the regioselective preparation of silyl enol ethers. Wilkinson s catalyst [(Ph3P)3RhCl] is suitable to promote the reaction and subsequent hydrolysis provides the saturated carbonyl compound, as illustrated by the... 

Silanes have also found use in colloid preparation. An interesting example for the use of organosilanes in the formation of organosols of transition metals is the reduction of platinum(II) complexes, especially cyclooctadieneplatinum dichloride, to colloidal platinum by trialkoxysilanes and trialkylsilanes. Hus was reported by Lewis and coworkers [60] who demonstrated that the presumably homogeneous hydrosilylation catalysts formed from platinum compounds in the presence of silanes were in fact colloidal in nature, and raised the prospect for colloid activity in many homogeneous catalyst systems (see Section 6.5). The same reduction method with organosilanes has been used for the preparation of colloids of rhodium and palladium. [61]... 

Fluorinated aldehydes are prepared in high yield by reaction of readily available acid chlorides with trialkylsilanes in the presence of Pd/C catalyst. Since no solvent is used, simple separation from by-product chlorosilane provides pure aldehyde. Previously reported syntheses are inconvenient, not easily amenable to scale-up, or require separate dehydration steps. Polymerization reactions of these aldehydes are described. Aluminum and titanium alkoxides initiate polymerization by a coordination mechanism. With selected examples, polymerization and appropriate end-capping affords soluble, high molecular weight polyacetal stable to ca. 300 ° C. 

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