Tris trimethylsilyl methane

Carbonyl Additions. The reagent is a useful nucleophilie trimethylsilyl transfer agent.Enones and enals undergo 1,2-addition in ether at room temperature, while 1,4-addition occurs at —78 °C (eq 1). Ester carbonyls, which are amenable to attack only in boiling ether in the presence of aluminum chloride, give Q, Q -bis(trimethylsilyl)alkanols.  

Functionalized acylsilanes are accessible by the reaction of (Me3Si)3 Al-OEt2 with (5)-2-pyridyl esters in the presence of stoichiometric copper(I) cyanide (eq 2).  

Silylalumination of Alkynes. Silylalumination of 1-alkynes provides a convenient entry to vinylsilane derivatives in a regio-and stereoselective manner (eq 3).  

Transition Metal Promoted Coupling Reactions. In the presence of a Ni catalyst, the reagent undergoes cross-coupling reactions with aryl bromides (eq 4). Alkenyl iodides are stere-ospecifically converted to alkenylsilanes in the presence of a Pd catalyst (eq 5). 

Allylic acetates are converted to allylsilanes in the presence of Pd complexes or hexacarbonylmolybdenura The regioselectivity depends on the catalyst. The Mo° catalyst leads to products with the silyl group attached to the less-hindered end of the allyl group. The regioselectivity of the Pd°-catalyzed reaction depends on the solvent and, in particular, on the ligands. The two catalysts also differ with respect to stereochemistry (eq 6).  

Me3SiCl + 2Li — (Me3Si)Li - - LiCl 3(Me3Si)Li -I- CHCI3 — (Me3Si)3CH + 3LiCl 

The reaction mixture is stirred overnight at room temperature by which time it assumes a clear orange-red color. Refluxing the solution for an additional 4h destroys any unreacted MeLi and results in the development of a deep red color. Upon cooling to room temperature the (Mc3Si)3CLi will remain stable for periods up to 24 h. 

Submitted by ALAN H. COWLEY, NICHOLAS C NORMAN, and MAREK PAKULSKI  

2RPCI2 + 4Na[CioHg] — RP=PR + 4NaCl + 4CioHg R = (Me3Si)3C or 2,4,6-f-Bu3CeH2 

This method is suitable only for small scale (S mmol or less) preparations of these diphosphenes because of the difficulties involved in removing larger quantities of naphthalene from the product. 

This is a modification of the procedure published by Issleib et al. To a 500-mL round-bottomed flask is added lOOmL of THF, 17 mL of Et20, (Me3Si)3CH (18.25 g, 78.6 mmol) and (dropwise) 62 mL of 1.4 M (86.8 mmol) MeLi (Aldrich) in Et20 solution. 

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Aluminum chloride-catalyzed intramolecular rearrangement of l-(di-chloromethyl)heptamethyltrisilane followed by methylation gives tris-(trimethylsilyl)methane in 72% overall yield (158). 

Tris(trimethylsilyl)methyllithium (88), prepared from methyllithium and tris(trimethylsilyl)methane in THF, can be recrystallized from toluene to give colorless, transparent needles of the unique ate complex [Li(THF)4] [Li C(TMS)3 2] . The structure of one of the anions in this complex is shown as (89). This... 

Reaction of tris(trimethylsilyl)methyllithium, generated from tris(trimethylsilyl)methane and butyllithium, with phenyloxirane gave 2-phenyl-l,l-bis(trimethylsilyl)cyclopropane (1) in good yield. 

Most recently, a C system was developed using tris(trimethylsilyl-methane), which can be added to any solution. The compound is stable under basic, acidic, oxidizing and reducing conditions, and can be removed chromatographically. The temperature-dependent resonances move across the... 

Tris(trimethylsilyl)silane is much more acidic than tris(trimethylsilyl)methane (p a = 36.8) and triphenylsilane (p Ta = 35.1). Can you think of an explanation for these relative acidities Also, can you suggest a rationale for the high acidity of trichlorosilane (recall that it can be deprotonated by triethylamine). 

Amino) (alkyl) (fluoro)[bis(trimethylsilyl)methyl]silanes [365] have been obtained by allowing the lithiated tris(trimethylsilyl)methane to react first with trifluoroorga-nosilane and then with lithium bromide. 

Synthesis of Tris(trimethylsilyl)methyl Bromide. Tris-(trimethylsilyl)methyl bromide (trisyl bromide) can be prepared in 75% yield by photochemical bromination of neat tris(trimethylsilyl)methane at 180-190 °C in less than 5 h (eq 1). 

Metalation. Tris(trimethylsilyl)methyllithium can be prepared by metalation of tris(trimethylsilyl)methane by methyl-lithium in a mixture of diethyl ether and THF (eq 2). An improved procedure is described as follows. To a solution of tris(trimethylsilyl)methane in THF is added a solution of MeLi (10% excess) in diethyl ether with stirring under nitrogen. The diethyl ether is distilled off and the residual solution is boiled under reflux under nitrogen. After 2 h, about 95% of tris(trimethylsilyl)methane is converted to tris(trimethylsilyl)methyllithium. Tris(trimethylsilyl)-methyllithium is important for the introduction of (Mes Si)3C (trisyl) groups, and for use in Peterson alkenations (eq 3). 

Formation of Bis(trimethylsilyl)methyllithium. The carbon-silicon bond of tris(trimethylsilyl)methane can be cleaved by lithium methoxide in HMPA to formbis(trimethylsilyl)methyl-lithium, which subsequently reacts with carbonyl compounds to form alkenes (eq 4). ... 

Similar cleavage of the Si-C bond occurs with fluoride ion. The in situ reaction with carbonyl compounds gives the corresponding alkenes. Thus the reaction of tris(trimethylsilyl)methane with nonenolizable carbonyl compounds in the presence of tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) gives the corresponding alkenes in excellent yield (eq 5). ... 

Bis(trimethysilyl)methane derivatives react with aldehydes and ketones in the presence of a fluoride ion to afford di- and trisubstituted alkenes in one pot [56]. The reaction involves the fluoride-catalyzed carbonyl addition followed by Peterson elimination. For example, a,a-bis(trimethylsilyl)acetonitrile 153 produces /3-phenylacrylonitrile 154 with high -selectivity, whereas tris(trimethylsilyl)-methane 155 reacts with anisaldehyde at room temperature to give alkenylsilane 156 (Scheme 5.39). 

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