Triethylsilane trifluoroacetic acid

The triethylsilane/trifluoroacetic acid reagent system reduces alkenes to alkanes in poor to excellent yields depending largely on the ability of the alkene to form carbocations upon protonation. Under these conditions the more substituted olefins are reduced in better yields and styrene double bonds are reduced in high yields.127,202,207,221-228 The reduction of 1,2-dimethylcyclohexene with this reagent gives a mixture of cis- and trans- 1,2-dimethylcyclohexane.229 The formation of the trifluoroacetate esters is a side reaction.205,230... 

In addition to the dihydro compounds discussed above, the triethylsilane/trifluoroacetic acid reduction system can also be used to prepare tetrahydro pyrimidine derivatives, especially when dichloromethane is used as the solvent <2004TL2107>. Thus, treatment of 2-amino-5-phenylpyrimidine 398 with 2.5 equiv of triethylsilane and 5 equiv of TEA in dichloromethane at room temperature gave a quantitative yield of the tetrahydro derivative 399, whereas only a dihydro derivative was obtained with 10 equiv of the silane in the absence of dichloromethane <2004TL2107>. 

Alternatively, the imide-acid chloride is reacted with methanol to give the imide ester which, after borohydride reduction and triethylsilane/trifluoroacetic acid treatment, furnishes the bicyclic lactam 6 as a racemate. The latter is acylated with either propanoyl chloride or 3-phcnylpropanoyl chloride and the resulting amides 7 deprotonated and alkylated with (bro-momethyljbenzene or iodomethane, respectively, to give the major alkylation products 8 with d.r. >98 2 and in 65% yield3. 

Unsaturated ketonucleosides have been shown to be remarkably stable under acidic conditions. 7-(3-0-Acetyl-4,6-dideoxy-/ -L-g/t/cm>-hex-3-enopyranosyl-2-ulose)theophylline (61a) proved to be stable in 0.1 M hydrochloric acid, as no glycosylic cleavage had occurred51 after 20 h. Similarly, no decomposition was observed when 7-(3,6-di-0-ace-tyl-2-deoxy-/ -D-gh/cero-hex-2-enopyranosyl-4-ulose)theophylline (66) was treated with 0.1 M sulfuric acid during 48 h at room temperature, and attempted, ionic hydrogenation with triethylsilane - trifluoroacetic acid failed.31... 

Cleavage of N-carbobenzoxy groups Triethylsilane. Trifluoroacetic acid. 

Grieco took advantage of such a cycloreversion for the A -methylation of amino acid derivatives and dipeptides by trapping the incipient iminium ion with triethylsilane/trifluoroacetic acid without loss of chirality (Scheme 12) [67]. 

Triethyl phosphite, 170, 373,501 Triethyl phosphonocrotonate, 337 Triethylsilane-Boron trifluoride, 501 Triethylsilane-Trifluoroacetic acid, 502... 

Related Reagents. Phenylsilane-Cesium Ruoride Tri-n-butylstannane Tricarbonylchloroiridium-Diethyl(methyl) Silane-Carbon Monoxide Triethylsilane-Trifluoroacetic Acid. 

En route to a new synthesis of the ergoline skeleton, Parker and colleagues developed a new cyclization of 4-unsubstituted indoles. Indole 235 was reduced to a mixture of indoline epimers under standard triethylsilane/ trifluoroacetic acid conditions proteaion of indoline 236 with benzoyl chloride delivered 237 in 85% yield over two steps. Finally, palladium-catalyzed cyclization afforded desired tetracyclic indole structure 238 in 86% yield (130L2598). 

Sodium cyanoborohydride-acetic acid and triethylsilane-trifluoroacetic acid have been found to be excellent reducing systems for oxime benzoates, providing a new general synthesis of O-acylhydroxylamines (Scheme 38). ... 

Diarylpropanes are obtained from chalcone-type ketones by allowing a mixture of ketone/triethylsilane/trifluoroacetic acid, 1/3/5 or 1/3/10 to react [548] (Eq. 4.13) ... 

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