Trimethylchlorosilane

Trimethylsilylation with trimethylchlorosilane affords the corresponding allene derivative, hydroxyalkylation with aldehydes and ketones gives mixtures of comparable amounts of acetylenic and allenic carbinols. 

To a solution of 0.50 tnol of ethyllithium in about 450 tnl of diethyl ether (see Chapter II, Exp. 1) was added 0.20 mol of 1-heptyne or butylallene (see Chapter VI, Exp. 1) with cooling below Q°C. After the addition the cooling bath was removed and the thermometer-gas outlet combination was replaced with a reflux condenser. The solution was heated under reflux for 6 h. The thermometer-gas outlet was again placed on the flask and the yellow suspension was cooled to -50°C. Trimethylchlorosilane (0.20 mol) was added dropwise in 10 min, while keeping the temperature between -40 and -35°C. After having kept the mixture for an additional 30 min at -30°C, it was poured into 200 ml of ice-water. The aqueous layer was extracted three times with small portions of diethyl ether. 

A solution of about 1.1 mol of ethynylmagnesium bromide (note 1) was cooled to -50°C and 1.0 mol of trimethylchlorosilane was added in 15 min with cooling between -5 and +5°C. After the addition stirring at 0-5°C was continued for 2 h. The mixture was allowed to stand at room temperature overnight (6 h will probably be sufficient). The mixture was then poured into 1 1 of l N HCl. High-boiling light petroleum (b.p. > 180°C) (250 ml) v/as added and the mixture was shaken... 

To absolution of 1.00 mol of ethyl lithium in 800-900 ml of diethyl ether (see Chapter II, Exp. 1) was added, with cooling between -20 and -10°C, 0.50 nol of dry propargyl alcohol, dissolved in 100 ml of diethyl ether. Subsequently 1.1 mol of trimethylchlorosilane was introduced over a period of 25 min with cooling between -15 and +5°C. After stirring for an additional 2 h at about 30°C the suspension was poured into a solution of 30 g of acetic acid in 150 ml of water. After stirring for 1 h at room temperature the layers were separated and the aqueous layer v/as extracted four times with diethyl ether. The combined ethereal solutions were washed with sodium hydrogen carbonate solution in order to neutralize acetic acid, and were then dried over magnesium sulfate. The diethyl ether was removed by evaporation in a water-pump vacuum and the residue distilled... 

The distillate was dissolved in a mixture of 350 ml of dry diethyl ether and 45 g of dry triethylamine (dried over powdered KQH). Trimethylchlorosilane (45 g) was added in 20 min with cooling at about 10°C. After standing for 1 h at room temperature the precipitate was sucked off on a dry sintered-glass funnel and rinsed with pentane. The filtrate was concentrated in a water-pump vacuum- The small amount of salt which precipitated during this operation was removed by a second suction filtration. Subsequent distillation afforded the trimethyl silyl ether, b.p. 100°C/15 mmHg, 1.4330, in 944 yield. 

MQ resins are commercially manufactured by one of two processes the ethyl sihcate or the sodium sihcate process. In the ethyl sihcate process, these resins were first prepared by cohydrolysis of tetraethoxysilane and trimethylchlorosilane in the presence of an aromatic solvent (eq. 34). This process is versatile and reproducible it can be used to prepare soluble MQ resins with M/Q ratios ranging between 0.6 and 4. The products of these reactions typically contain high levels of residual alkoxysilane groups. 

A more economical route to MQ resin uses low cost sodium sihcate and trimethylchlorosilane as inputs (eq. 35) (395). The sodium sihcate process is initiated by acidifying an aqueous sodium sihcate solution to a pH of 2. The resulting hydrosol quickly builds molecular weight. The rate of this increase is moderated by the addition of an alcohol such as 2-propanol. The hydrosol is subsequentiy silylated by the addition of trimethylchlorosilane. This process, which is kinetically sensitive and limited to synthesizing M/Q ratios of 1 or less, is preferred when MQ resins having high (>1%) OH content are required (395). 

Trimethylsilyl iodide [16029-98-4] (TMSI) is an effective reagent for cleaving esters and ethers. The reaction of hexamethyldisilane [1450-14-2] with iodine gives quantitative conversion to TMSI. A simple mixture of trimethylchlorosilane and sodium iodide can be used in a similar way to cleave esters and ethers (8), giving silylated acids or alcohols that can be Hberated by reaction with water. 

Tyifluorovinyllithium on reaction with trimethylchlorosilane yields a tri-methylsilyltrifluoroethylene, which itself is a new and useful synfhon for the preparation of difluorovmylic compounds [66] (equation 33)... 

Prepare a solution of the silanation agent. For trimethylchlorosilane, use toluene as the solvent. The minimum requirement of the silanation agent is calculated by assuming the surface density of silanol to be one functionality per 0.1 nm. ... 

If a bulky silanation agent such as octyidimethylchlorosilane is used, there will be unreacted silanols left. These silanols can be end capped by reacting the silica beads with trimethylchlorosilane by repeating steps 4-7. 

Intramolecular cyclization of 2-phenysulfonylmethyl lactam 3 took place upon reaction with lithium hexamethyldisilazan via generating its a-sulfonyl carbanion to give a cyclized postulated intermediate that can be quenched with trimethylchlorosilane to afford the stable silyl ketal 4. The later ketal was desulfonylated by Raney-Ni and desilylated through treatment with tetrabutyl ammonium fluoride (BU4NF) to afford the carbacephem 5 (94M71) (Scheme 1). 

Another acylated ampicillin derivative with expanded antimicrobial spectrum is piperacil1 in (19). Its synthesis begins with 1-ethyl-2,3-diketopiperazine (j7, which itself is made from ]i-ethylethylenediamine and diethyl oxalate), which is activated by sequential reaction with trimethylchlorosilane and then trichloromethyl chioroformate to give This last... 

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