Toluene, trimethylsilylation

Benzyllithium)2-TMEDA in Toluene. Trimethylsilyl chloride. Added trimethylsilyl chloride dissolved in ether at —5°C over 1 hr let... 

Subsequently it was found that trimethylsilyl azide in triflic acid is a more efficient and improved reagent for aminations (169). Amination of toluene in the presence of trichloramine—A1 CL proceeds predominantly at the / -position. 

To a solution of 310 mg (1.18 mmol) of 4-[(Z)-5-(trimethylsilyl)-3-pentenyl]-3-vinyl-2-cyclohcxcnone in 20 mL of toluene is added at —78, JC 0.75 mL (2.75 mmol) of a 50% solution of ethylaluminum dichloride in hexane. After stirring for 2 h at — 78 C. the mixture is quenched by addition of 20 mL of sat. aq NaHC Oj. After washing with 20 mL of brine the organic phase is extracted with three 30-mL portions of diethyl ether and dried over MgS04. The solvent is removed and the crude product is flash chromatographed (silica gel, EiOAc/petroleum ether 1 9) yield 114 mg (60%). 

The following abbreviations are commonly used for substituent groups in structural formulae Ac (acetyl), Bn or PhCH2 (benzyl), Bz or PhCO (benzoyl), Et (ethyl), Me (methyl), Me3Si (not TMS) (trimethylsilyl), Bu Me2Si (not TBDMS) (rerf-butyldimethylsilyl), Ph (phenyl), Tf (triflyl = trifluoromethanesulfonyl), Ts (tosyl = toluene-p-sulfonyl), Tr (trityl). 

Heteropolycyclic compounds were obtained [29] by treating bromo furylethers with tris-(trimethylsilyl)silane (TTMSS) in hot toluene containing a catalytic amount of AIBN (Equation 1.12). 

The cyclopropanation of 1-trimethylsilyloxycyclohexene in the present procedure is accomplished by reaction with diiodomethane and diethylzinc in ethyl ether." This modification of the usual Simmons-Smith reaction in which diiodomethane and activated zinc are used has the advantage of being homogeneous and is often more effective for the cyclopropanation of olefins such as enol ethers which polymerize readily. However, in the case of trimethylsilyl enol ethers, the heterogeneous procedures with either zinc-copper couple or zinc-silver couple are also successful. Attempts by the checkers to carry out Part B in benzene or toluene at reflux instead of ethyl ether afforded the trimethylsilyl ether of 2-methylenecyclohexanol, evidently owing to zinc iodide-catalyzed isomerization of the initially formed cyclopropyl ether. The preparation of l-trimethylsilyloxybicyclo[4.1.0]heptane by cyclopropanation with diethylzinc and chloroiodomethane in the presence of oxygen has been reported. "... 

The diacetal 629, prepared from the carbonyl compound and O-silylated allylic alcohols in the presence of TMSOTf 20, reacts with ( )-l-trimethylsilyl-2,4-penta-diene 630, in the presence of TMSOTf 20 in CH2CI2 at -78°C, to afford 60% 631 this undergoes Diels-Alder-cyclization at 170 °C in toluene to give a substituted... 

A mixture of sarcosine (45 mg, 0.5 mmol) and bis(trimethylsilyl)acetamide 22a (272 iL, 1.1 mmol) in 0.5 mL acetonitrile is stirred at room temperature for 1 h and at 40 °C for 30 min to give 441, which is then combined with a solution of the glyoxamide 440 in 1 mL abs. toluene. The resulting mixture is heated under reflux for 18 h, cooled, diluted with CHjClj, washed with 1 M NaOH, and the aqueous layer is extracted with CH2CI2. The combined organic layers are washed with brine, dried, concentrated, and purified by chromatography to give 40 mg (40%) 444 as a yellowish oil [49] (Scheme 5.89). 

Pyrroles can also be prepared by 1,3-dipolar cycloaddition of C-trimethylsilyl amides such as 1497 with dimethyl acetylenedicarboxylate in boihng toluene to give, via the azomethinimide 1498, 78% 1499 [45]. On employing a threefold excess of dimethyl acetylenedicarboxylate the cycloadduct 1499 is obtained in nearly quantitative yield [45] (Scheme 9.26). 

In this section primarily reductions of aldehydes, ketones, and esters with sodium, lithium, and potassium in the presence of TCS 14 are discussed closely related reductions with metals such as Zn, Mg, Mn, Sm, Ti, etc., in the presence of TCS 14 are described in Section 13.2. Treatment of ethyl isobutyrate with sodium in the presence of TCS 14 in toluene affords the O-silylated Riihlmann-acyloin-condensation product 1915, which can be readily desilylated to the free acyloin 1916 [119]. Further reactions of methyl or ethyl 1,2- or 1,4-dicarboxylates are discussed elsewhere [120-122]. The same reaction with trimethylsilyl isobutyrate affords the C,0-silylated alcohol 1917, in 72% yield, which is desilylated to 1918 [123] (Scheme 12.34). Likewise, reduction of the diesters 1919 affords the cyclized O-silylated acyloin products 1920 in high yields, which give on saponification the acyloins 1921 [119]. Whereas electroreduction on a Mg-electrode in the presence of MesSiCl 14 converts esters such as ethyl cyclohexane-carboxylate via 1922 and subsequent saponification into acyloins such as 1923 [124], electroreduction of esters such as ethyl cyclohexylcarboxylate using a Mg-electrode without Me3SiCl 14 yields 1,2-ketones such as 1924 [125] (Scheme 12.34). 

Trimethylsilyl esters of tris(thio)phosphonic acids 2070 are readily oxidized by DMSO in toluene at -30 °C to give the dimeric tetra(thia)diaphosphorinanes 2071 and HMDSO 7 [208] (cf. also the oxidation of silylated thiophenol via 2055 to diphenyl disulfide). The polymeric Se02 is depolymerized and activated by reaction with trimethylsilyl polyphosphate 195 to give the corresponding modified polymer... 

The intermolecular Pauson-Khand reaction of the resulting S/P-cobalt complexes with norbornadiene was studied under thermal and A -oxide activation conditions. Thus, heating the diastereomerically pure complex (R = Ph, R = Cy) with ten equivalents of norbornadiene at 50 °C in toluene afforded the corresponding exo-cyclopentenone in a quantitative yield and with an enantio-selectivity of 99% ee. Under similar conditions, the analogous trimethylsilyl complex (R = TMS, R = Cy) afforded the expected product in a high yield but with a lower enantioselectivity of 57% ee. In order to increase this enantio-selectivity, these authors performed this reaction at room temperature in dichloromethane as the solvent and in the presence of NMO, which allowed an enantioselectivity of 97% ee to be reached. These authors assumed that the thermal activation promoted the isomerisation of the S/P ligand leading to a nonstereoselective process. 

BSTFA provided the highest yield of product in comparison to other silylating agents. BSA [bis(trimethylsilyl)acetamide] reacted with DDQ. TMSOTf with luti-dine or collidine in toluene offered the best alternative but the yield was lower than the yield achieved with BSTFA. 

PPTS, Pyridinium p - toluene s u I fo n ate SE, 2-Trimethylsilylethyl TBDMS, ferf-Butyl-dimethylsilyl TBDPS, ferf-Butyldiphenylsilyl TEMPO, 2,6,6-Tetramethyl-l-piperidi-nyloxy Tf, Trifluoromethanesulfonyl THF, Tetrahydrofuran THP, Tetrahydropyran TIPDS, l,l,3,3-Tetraisopropyl-l,3-disiloxanyl TMS, Trimethylsilyl. 

In 2002, Leadbeater and Torenius reported the base-catalyzed Michael addition of methyl acrylate to imidazole using ionic liquid-doped toluene as a reaction medium (Scheme 6.133 a) [190], A 75% product yield was obtained after 5 min of microwave irradiation at 200 °C employing equimolar amounts of Michael acceptor/donor and triethylamine base. As for the Diels-Alder reaction studied by the same group (see Scheme 6.91), l-(2-propyl)-3-methylimidazolium hexafluorophosphate (pmimPF6) was the ionic liquid utilized (see Table 4.3). Related microwave-promoted Michael additions studied by Jennings and coworkers involving indoles as heterocyclic amines are shown in Schemes 6.133 b [230] and 6.133 c [268], Here, either lithium bis(trimethylsilyl)amide (LiHMDS) or potassium tert-butoxide (KOtBu) was em-... 

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