Butyl trimethylsilylmethyl

Addition reactions such as A-alkylation do not occur readily, and trimethylsilylmethylation of 3,4-diphenyl-l,2,5-thiadiazole 8 with trimethylsilylmethyl trifluoromethanesulfonate at 80°C occurred at N-2 < 1999J(P1) 1709>. The electron-rich 3-hydroxy-l,2,5-thiadiazole can be preferentially methylated on N-2 using trimethyl orthoacetate in toluene to afford the 2-methyl-l,2,5-thiadiazol-3-one in 69% yield <2002EJ01763>, although a mixture of 3-hydroxythiadiazole and neat trimethyl orthoacetate showed a 20 80 ratio of N- versus 0-alkylation products by H NMR. Treatment of 3-hydroxy-l,2,5-thiadiazole with /-butyl acetate under acid catalysis (Amberlyst 15) gave almost exclusively the A-alkylated compound <2002BMC2259>. 

This route has, for example, been used to make the butyl compounds.15 The trimethylsilylmethyl derivatives have also been made1617 they can be precipitated from cyclohexane, washed free from organomercury starting materials, and obtained without organometal-alkoxide contaminants. Alternatively, KCH2SiMe3 may be used in situ, e.g., for metallation of alkenes.18... 

Methyl, butyl, or trimethylsilylmethyl compounds of Na, K, Rb, or Cs can be used to generate other organometallic compounds by alkyl group exchange. 

Sieburth and Somers82 studied the product ratio of metallation of t-butyl-lV-phenyhnethyl-V-trimethylsilylmethyl carbamate 68 (equation 26). This ratio reflects the relative abilities of an a-phenyl and a-trimethylsilyl group to stabilize an adjacent carbanion. It was found that metallation a to silicon (70) was slightly favoured kinetically, but at equilibrium the a-phenyl anion 69 was strongly favoured. 

Ligand exchange reactions of monodentate amides, iodides, or alkoxide complexes with other amides, alkoxides as well as sulfides, and carbon ligands has been documented [23,25]. A rather unique reaction of a trimethylsilylmethyl ligand bound to a chromium nitride has been reported thus, reaction of tert-butyl isocyanide with 52 is reported to furnish 53 (Eq. (17)). 

Allyl > cyanomethyl benzyl methyl > phenyl cyclopropyl ethyl n-butyl o-fluorophenyl trimethylsilylmethyl per-fluorophenyl... 

By reacting directly with the alkali metal, organomercury compounds are commonly used to synthesize organoalkali metal compounds of the heavier alkali metals. This route has been used to make various alkyl compounds, such as butyl and trimethylsilylmethyl derivatives (equation 10). 

Enantioselective Reduction ofa,P-Ynones. Oxazaborolidine ligands 1 are among the most effective catalysts for the enantioselective reduction of ketones to secondary alcohols. Substitution of the methyl or butyl group on boron by a trimethylsilylmethyl group led to a much improved catalyst for the catecholborane mediated reduction of a, 3-ynones. For example, the enantioselectiv-ities for the reduction of an a, 3-ynone was improved from 60% to 98.5% when the nature of the R group was modified (eq 1). ... 

The initial asymmetric synthesis (see Scheme 5.2) of pyrrolidine acid 3 suffered from a chiral HPLC bottleneck. As a result, chiral salt resolution was investigated. The rapid discovery of a crystalline di-p-toluoyl-D-tartaric acid salt provided the necessary means to resolve and purify the desired diastereomer. Using 0.65 equivalent of the acid in methyl (cr(-butyl ether (MTBE), the crystallized salt was shown to be a 92 8 ratio of (3S,4R) (3R,4S) diastereomers. The resolved tartaric acid salts were then recrystalhzed from n-butanol to ratios of >99 1 in a 42% overall yield on a 2-kg scale. Further improvements were made in the preparation of the azomethine ylide precursor 38. In step 1, using dimethyl sulfoxide (DMSO) as the solvent, the reaction temperature of trimethylsilylmethylation of tert-butylamine was lowered from 200°C used in the original synthesis to 80°C. In step 2, substituting n-butanol in place of methanol reduced the amount of oligomerization observed and increased the yield to 69%. Overall, these improvements allowed for the preparation of pyrrolidine acid 3 in 22% overall yield in 99% ee from cinnamate 39 (Scheme... 

Use of the methylsulphinyl carbanion as base is recommended for the synthesis of ethers from alcohols and alkyl halides. The catalysed formation of dimethyl ether from hydrogen and carbon dioxide has been reported. Carey has described the use of the silicon-modified organolithium reagent (73) in the preparation of vinyl thioethers (Scheme 151). In order to extend the scope of this reaction to include vinyl ethers themselves, an attempt was made to metalate trimethylsilylmethyl ether use of n-buty 1-lithium resulted in nucleophilic attack on silicon, whereas t-butyl-lithium abstracted the wrong proton, as shown in Scheme 151. 

A highly convenient method of generating trimethylsilylmethyl-lithium, a reagent for methylenation (Peterson olefination) of ketones and aldehydes, has been discovered. Transmetallation between the readily available (trimethylsilyl-methyl)tributyltin and n-butyl-lithium in a mixture of hexane and THF furnishes the reagent in quantitative yield at 0 °C in 30 min. ... 

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