Dimethylsilyl

An acetylene-alkylidene rearrangement with 1,2-silyl migration was suggested to occur during the pyrolysis of l-dimethylsilyl-2-(dimethylsilylethynyl)benzene 25, which gave 3-(dimethylsilyl)-l-silaindene 26 in addition to silaindenes 27 and 28 (equations 16 and 17)43. 

Dimethylsilyl ethers possessing alkenyl and aryl radical precursors... 

N-(Thexyl dimethylsilyl)dimethylamine (N-[2,3-dimethyl-2-butyl]dimethylsilyl dimethyl-amine) [81484-86-8] M 187.4, b 156-160°/720mm. Dissolve in hexane, filter, evaporate and distil. Colourless oil extremely sensitive to humidity. It is best to store small quatities in sealed ampoules after distillation. For estimation of purity crush an ampoule in excess O.IN HCl and titrate the excess acid with O.IM NaOH using methyl red as indicator. [Helv Chim Acta 67 2128 1984.]... 

Bradshaw and Hui, in their review of sulfur-containing macrocycles, have included the analog of compound 7 (this chapter) in which each carbon bridge is replaced by a dimethylsilyl bridge. Nevertheless, silicon-containing crown relatives remain rare. 

Hydroxystyryl)dimethylsilyl Ether (HSDMS-OR) and (2-Hydroxystyryl)diisopropylsilyl Ether (HSDIS-OR)... 

A/ HE, 0.1 M NaF, pH 5. THE, 25°, 2 days, 77% yield. In this substrate, a mixture of products resulted from the attempted cleavage of the t-butyl-dimethylsilyl ether with tetra-n-butylammonium fluoride, the reagent generally used. ... 

The introduction of a (dialkylamino)dimethylsilyl or dimethylphenylsilyl group makes it possible to introduce a hydroxy group stereospecifically by Tamao oxidation78 80. This was successfully applied in the synthesis of /rrw.y-4-hydroxy-5-alkylfuranones81. 

Butanol, l,l-dichloro-3-[[(l,l-dimethylethyl)dimethylsilyl]oxy]-, 4-methylbenzene sulfonate, (3S)-... 

C,, H2c,N04SSi 106560-32-1) see Faropenem sodium [15-[lo(45, 6S ),2a,6p,8P,8att]]-4-n(l,1-dimethyl-ethyl)dimethylsilyl]oxy]-6-[2-(lA6,7,8,8a-hexahydro-8-hydroxy-2,6-dimethyl-l-naphthalenyl)ethyl]tetrahydro-2ff-pyran-2-one... 

Difunctional reagents, for example the very cheap dimethyldichlorosilane 48, which is produced on a large technical scale, and the much more reactive and expensive dimethylsilyl bis(O-triflate) 49 [65-67] (Scheme 2.8) convert alcohols or phenols 11 in the presence of bases, for example triethylamine or DBU, into the silylated compounds 50. Thus 48 and 49 and other bifunctional reagents such as di-tert-butyldichlorosilane [68] or di(tert-butylsilyl)-bis(0-triflate) [69] and the subsequently described 51 and 52 combine two alcohols to silicon-tethered molecules 50, which can undergo interesting intramolecular reactions [70-74]. 

Because the trimethylsilyl enol ether of cyclohexanone 107 a is considerably more bulky than the corresponding dimethylsilyl enolate 107b, only the latter reacts with the N-tosyhmine 108 in the presence of catalytic amounts of diisopropylamine in DMF/H2O at 78°C or at room temperature to give the Mannich type compounds 109 in high yields [39] (Scheme 3.4). 

Whereas 2-methylpyridine-N-oxide 881a reacts rather slowly with TCS 14/ NaCN/NEt3 in DMF at 100-110°C, sterically hindered 2-methoxycarbonyl- 881b, 2-isopropyl- 881c, or 2-tert-butylpyridine-N-oxide 881d have not yet been reacted in the presence of NEts or DBU in DMF with the much less bulky but apparently as yet unknown dimethylsilyl cyanide Me2HSiCN 883 (which can probably be gener-... 

Silica sol-gel inunobihzed La(OTf)3 (Scheme 48.2B) previously used in the acylation of a series of alcohols and activated aromatic compounds using acetic anhydride as acylating agent, showed a poor activity compared with other various sihca sol-gel inunobihzed triflate derivatives (tert-butyl-dimethylsilyl-trifluoromethane-sulfonate (BDMST), or trifhc acid (HOTf)). Acylation at the aromatic ring occurred over the BDMST and HOTf catalysts, while the La(OTl)3 catalysts only led to O-acetylated products [22]. Such behavior is characteristic... 

It has also been shown that dimethylsilyl enolates can be activated by diisopropylamine and water and exhibit a high reactivity toward iV-tosyl imines to give Mannich-type reaction products in the absence of a Fewis acid or a Bronsted acid.51 For example, the reaction of [(1-cyclohexen-l-yl)oxy]dimethylsilane with 4-methyl-A -(phenylmethylene)benzene sulfonamide gave re/-4-methyl-N- (f )-[(15)-(2-oxocyclohexyl)phenyl-methyl] benzenesulfonamide (anti-isomer) in 91% yield stereoselectively (99 1 anti syn) (Eq. 11.30). On the other hand, Fi and co-workers reported a ruthenium-catalyzed tandem olefin migration/aldol and Mannich-type reactions by reacting allyl alcohol and imine in protic solvents.52... 

A further extension to this concept was (dimethylsilyl)propionic acid linker 75 used for the solid-phase synthesis of aryl-containing organic compounds [86], The linker was cleaved smoothly with TFA and has been used for the synthesis of compounds which involved alkylation, acylation, and Mitsunobu reactions. 

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