T-Butyldimethylsilane

A mixture of the a/J-unsaturated ester (14mmol), t-butyldimethylsilane (18 mmol) and tris(triphenylphosphine)rhodium(i) chloride (0.56 mmol) was placed in a pre-heated (100°C) oil bath, and the course of reaction monitored by i.r. spectroscopy. On completion (ca. 30 min) the product was isolated by direct distillation (60-88%). 

Nowick and Danheiser have employed the Horner-Emmons reaction of a-phosphon-oacyl silanes to prepare a,/l-unsaturated acyl silanes in 54-97% yields116. The a-phosphonoacetyl silane intermediate (21), prepared from a-iodoacetyl t-butyldimethylsilane through the Arbuzov reaction, undergoes enolate alkylation, for example using potassium t-butoxide and methyl iodide the alkylated products also underwent Horner-Emmons reaction (Scheme 53). 

Three modes of reaction of aldehydes with allylsilane bearing sterically demanding silyl substituents are mediated by the proper choice of Lewis acid (Eq. 39) [66a]. Thus, influenced by SnC, allyl-t-butyldimethylsilane reacts with aldehyde in 2 1 stoichiometry to afford a ketone derivative. In contrast, use of BF3 OEt2 leads to the formation of a 1,3-dioxane derivative, which is a 1 2 adduct. Furthermore, ZrCU-pro-moted [2 -r 2] cycloaddition of allylsilane and aldehyde fnmishes oxetanes in good yields [66b]. 

Cyano-t-butyldimethylsilane. This reagent can be prepared in 75% yield by reaction of t-butyldimethylchlorosilane with KCN in refluxing CH2CI2 catalyzed by 18-crown-6. 

Alloc] are converted into the t-butyldimethylsiloxycarbonyl function upon treatment with t-butyldimethylsilane and palladium (II)... 

Representative procedure for the gold-catalyzed cycloisomerization of a-hydroxyallenes in micelles. ((Cis-2,5-dihydro-5-isopropyl-3-methylfurcm-2-yl)methoxy)t-butyldimethylsilane ... 

A number of reductive biotransformations of acyl silanes into a-hydroxy silanes have appeared recently. Acetyl dimethylphenylsilane is converted into (/f)-(l-hydroxyethyl) dimethylphenylsUane by plant cell suspension cultures of Symphytum officinale L. and Ruta graveolens L. in low yields but in 81% ee and 6% ee, respectively . SUanol and disUoxane were observed as by-products. Microbial reduction of racemic acetyl t-butyldimethylsilane has been achieved using Trigonopsis variabilis (DSM 70714) and Corynebacterium dioxydans (ATCC 21766) on a 10- gramme scale with > 96% ee in each case and in up to 78% yield . Recently, Saccharomyces cerevisiae (DHWS 3), a commercially available form of bakers yeast, has been shown to reduce acetyl dimethylphenylsilane, again to (/ )-(1-hydroxyethyl) dimethylphenylsilane, in 40% yield and >99.5% ee . 

Alkylsilanes have been shown to be versatile deprotection reagents for the benzyloxycarbonyl group. This is achieved by treatment with Et3SiH/PdCl2,f or by reaction with tert-butyldimethylsilane/Pd(OAc)2 which allows the corresponding tert-butyldimethylsiloxy-carbonyl-protected amino acids to be isolated.t l... 

In a vial, l-(t-butyldimethylsilyloxy)-3,6-dimethylhepta-3,4-dien-2-oI (50.0 mg, 185 pmol) was dissolved in a 2% aqueous TPGS-750-M solution (1.5 mL) containing NaCl (263 mg, 3M) and treated with AuBrs (0.8 mg, 1.85 pmol) under air. After complete conversion (10 min, monitored by TLC), the reaction mixture was extracted with M-hexane. The solvent was removed under reduced pressure and the crude product was purified by flash column chromatography (Si02, cyclohexane/EtOAc, 10 1) to afford ((c/s-2,5-dihydro-5-isopropyl-3-methylfiiran-2-yl)methoxy)/-butyldimethylsilane (46.2 mg, 92%) as a yellow oil. ... 

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