Trimethylsilylmethyl trifluoromethanesulfonate

Another triflate ester that recently has found growing application in organic synthesis is commercially available trimethylsilylmethyl trifluoromethanesul fonate. This powerful alkylating reagent can be used for the synthesis of various methylides by an alkylation-desilylation sequence A representative example is the generation and subsequent trapping by 1,3-dipolar cycloaddition of indolium methanides from the corresponding indole derivatives and trimethylsilylmethyl trifluoromethanesulfonate [108] (equation 54)... 

Diaryl-l,2,3-thiadiazoles and 1,2,3-benzothiadiazoles have been alkylated at N-3 with trimethylsilylmethyl trifluoromethanesulfonate and treatment of these salts with cesium fluoride generate new l,2,3-thiadiazol-3-ium-3-methanide 1,3-dipoles (see Section 5.07.8.1) <1999J(P1)1415>. 

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>. 

Amino-5-methyl-l,3,4-thiadiazole 48 reacts with chloroacetone to give the N-alkylated thiadiazolimine 49 (Equation 4) <2000AF550> and iV-alkylation of the 2,5-diphenyl- and 2,5-dimethyl-l,3,4-thiadiazole 50a and 50b with trimethylsilylmethyl trifluoromethanesulfonate gave the corresponding 1,3,4-thiadiazolium salts 51 (Equation 5) <2002J(P 1)2851 >. A comprehensive study of the quarternization of the 2,5-disubstituted thiadiazoles has been covered in CHEC(1984) <1984CHEC(6)545>. 

Cycloaddition of thiazolium azomethine ylides with dialkyl acetylenedicarboxylates 61 provides another approach to pyrrolo[2,1 -bjthiazoles 64 <070L4099>. Quatemization of 2-methylthiothiazole with trimethylsilylmethyl trifluoromethanesulfonate (TMSChkOTf) and subsequent fluoride-induced desilylation of the resulting (trimethylsilyl)methylammonium salt generate the acyclic azomethine ylide 62. This ylide readily participates in 1,3-dipolar cycloadditions with acetylene derivatives 61 to give adducts 63, which undergo spontaneous elimination of methylmercaptan to give the A-fuse cl thiazoles 64. ... 

ALKENES l,l -Bis(diphenylphos-phino)ferrocene. Sodium pyridylsele-nate. Tri-n-butyltin hydride. Trimethyl-silylmethyllithium. Trimethylsilylmethyl trifluoromethanesulfonate. Zinc. 

SN NMR was used to assist in the characterization of the iV-trimethylsilylmethyl 3,4-diphenyl-l,2,5-thiadiazolium trifluoromethanesulfonate 20 <1999J(P1)1709>. 

The reaction of triboracyclobutanide 36 in [D8]THF with methyl trifluoromethanesulfonate in an NMR tube at —90 °C affords a mixture of C-boryldiboracyclopropane 37 and compound 38 in a 3 1 ratio. Compound 36 reacts with dichloro(trimethylsilylmethyl)borane to give a product mixture, from which compound 39 (yield 50%) can be separated by crystallization (Scheme 2) <2003AGE671>. 

Tsuge O, Kanemasa S, Kuraoka S, Takenaka Shigeori (1984) N-(Trimethylsilylmethyl)-pyridinium trifluoromethanesulfonates as facile precursors for nonstabihzed pyridinium methyhdes. Chem Lett 13 279-280... 

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