Dimethyl trifluoromethanesulfonate

Trifluoromethanesulfonic acid is miscible in all proportions with water and is soluble in many polar organic solvents such as dimethylformamide, dimethyl sulfoxide, and acetonitrile. In addition, it is soluble in alcohols, ketones, ethers, and esters, but these generally are not suitably inert solvents. The acid reacts with ethyl ether to give a colorless, Hquid oxonium complex, which on further heating gives the ethyl ester and ethylene. Reaction with ethanol gives the ester, but in addition dehydration and ether formation occurs. 

Trifluoromethanesulfonic acid (triflic acid) in toluene greatly activates the Diels-Alder reaction of benzaldehydes with dimethylated 1,3-butadienes [89] (Table 4.22). With mono-methylated 1,3-butadienes the reaction gives less... 

Frejd and co-workers utilized a different tactic for aniline cyclization by first employing a Heck-Jeffery protocol under solvent-free conditions to prepare o-amino dehydrophenylalanine derivatives from o-aminoaryl iodides with the former undergoing a spontaneous la cyclization-elimination sequence to afford 2-methoxycarbonyl indoles <06S1183>. Dimethyl(methylthio)sulfonium trifluoromethanesulfonate (DMTST) was used by the Okuma group to promote the cyclization of o-vinyl-A-p-toluenesulfonylanilide to N-tosylindole <06CL1122>. 

Alkenes with a 1,1-disubstitution pattern form tertiary carbocations upon treatment with a Brpnsted acid. Consequently, such compounds are often easily reduced (Eq. 72). An example of this is the formation of 2-methylpentane in 93% yield after only 5 minutes when a dichloromethane solution of 2-methyl-1-pentene and 1.4 equivalents of triethylsilane is treated with 1.4 equivalents of trifluoromethanesulfonic acid at —75°.216 Similar treatment of 2,3-dimethyl-l-butene gives a 96% yield of 2,3-dimethylbutane.216... 

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>. 

The synthesis of imidazo[2,Tc][l,2,4]triazolo-3-thiones has been investigated. For instance, the reaction of 1,2,4-triazoline-3-thione 361 <1995JHC275> with methyl trifluoromethanesulfonate affords the stable 3-methylmercapto-1,2,4-triazolium trifluoromethanesulfonate 362 in quantitative yield, which after treatment with sodium bicarbonate and bromine provides 6-bromomethyl-2,6-dimethyl-7-ethoxycarbonyl-2,3,5,6-tetrahydro-7//-imidazo[2,T4-[l,2,4]triazolo-3-thione 10 in 47% yield, via intermediate 363 (Scheme 36) <1996T791>. 

Synthesis of diazonium salts. The details of the synthesis of 4-N, N-dimethylaminobenzenediazonium trifluoromethanesulfonate (Dl) are described below. N, N-Dimethyl-p-phenylenediamine... 

Cyclohexene was purchased from Wako Pure Chemical Ltd. Japan, or Aldrich Chemical Company, Inc., and used after distillation from lithium aluminum hydride. Borane-dimethyl sulfide complex was obtained from Aldrich Chemical Company, Inc., and was used as received. Trifluoromethanesulfonic acid was purchased from Wako Pure Chemical Ltd. Japan or Aldrich Chemical Company, Inc., and used without purification. The checkers used a freshly opened ampule of trifluoromethanesulfonic acid for each run. 

By using (/ )-. Y, V-dimethyl-l-phenylethylarnine. alkenes of the opposite absolute configuration but, surprisingly, with different enantioselectivity are formed81. However, elimination with ( S i-A. jY-dimeLhyTl-phenylethylamine of the trifluoromethanesulfonate of cfs-cyclohex-ane-l,4-diol monomethoxymethyl ether gives the corresponding alkene with only 5% ee. 

Reductive cyclization of o-nitrophenylacetic acids is a very general method of oxindole synthesis (see Section 3.06.2.1.1 for the application of this method to indoles in general). The main problem is efficient construction of the desired phenylacetic acid. One method involves base-catalyzed condensation of substituted nitrotoluenes with diethyl oxalate followed by oxidation of the 3-arylpyruvate (equation 200) (63CB253). Nucleophilic substitution of o-nitrophenyl trifluoromethanesulfonate esters, which are readily prepared from phenols, by dimethyl malonate provides another route (equation 201) (79TL2857). 

Tris(l,2-bis(dimethylphosphino)ethane)rhenium(I) trifluoromethanesulfonate is a white solid which can be oxidized to the purple Re(II) analog. This Re(I) salt is soluble in methanol, ethanol, dichloromethane, acetone, dimethyl sulfoxide (DMSO), and acetonitrile, and insoluble in diethyl ether [N.B. This Re(I) complex is unstable in nitromethane, presumably suffering oxidation to Re(II)]. 

S)-2-Ethoxy-4-isopropyloxazoline, 129 Homoallylic alcohols Crotyldiisopinocampheylborane, 86 Dichlorobis( 1 -phenylethoxy) -titanium(IV), 12 Organotitanium reagents, 213 Tin(II) trifluoromethanesulfonate, 301 Homopropargylic alcohols Bis(2,4-dimethyl-3-pentyl) tartrate, 36... 

SILYLATION Bis(trimethylsilyl)urea. t-Butyldimethylchlorosilane. t-Butyldimethylsilyl trifluoromethanesulfonate. Chlorotrimethylsilane. Dimethyl(2,4,6-tri-f-butylphenoxy)chlorosilane. Ethyl trimethylsilylacctate. Ketene t-butyldimethylsilyl methyl acetal. N-Methyl-N-(/-... 

Resin bound monosaccharide 5 was glycosylated with pivaloate donor 6a in the presence of dimethyl(methylthio)trifluoromethanesulfonate (DMTST, Fig. 6). 

The 4,7-dimethoxy-2,2-dimethyl-l,3,2-benzodiselenastannole 321 was prepared from commercially available 1,4-dimethoxybenzene 320 by a sequence of tandem ortho-lithiation and selenation, and followed by dimethyltin protection in 28% yield (Scheme 51). Then, sequential treatment of the stannole 321 in THF with selenyl chloride, trimethylsilyl trifluoromethanesulfonate (TMSOTf), and samarium iodide gave crystalline 4,7-dimethoxybenzotri-selenole 42 in 75% yield <1996H(43)1843>. The structure was characterized by X-ray crystallographic analysis (Section 6.12.3.1). 

The cyclohexadiene complex 29 has been further elaborated to afford either the cydo-hexenone 34 or the cyclohexene 36 in moderate yields (Scheme 1) [21]. The addition of HOTf to 29 generates the oxonium species 33, which can be hydrolyzed and treated with cerium(IV) ammonium nitrate (CAN) to release the cyclohexanone 34 in 43 % yield from 29. Alternatively, hydride reduction of 33 followed by treatment with acid eliminates methanol to generate the r 3-allyl complex 35. This species can be trapped by the conjugate base of dimethyl malonate to afford a cyclohexene complex. Oxidative decomplexation of this species using silver trifluoromethanesulfonate liberates the cyclohexene 36 in 57 % overall yield (based on 29). 

Lithium butyltelluroselenolate is methylated by methyl trifluoromethanesulfonate. The butyl methylseleno tellurium is in equilibrium with dibutyl ditellurium and dimethyl diselenium2. 

Methyl and ethyl trifluoromethanesulfonates were used to alkylate dimethyl tellurium9,10. When a compound with two organotelluro groups linked by a chain of methylene groups is treated with methyliodide in acetone, both tellurium atoms are methylated11. 

Dimethyl-l,3-benzotellurazolium Trifluoromethanesulfonate1 10.5 g (43 mmol) 2-methylbenzotelIura-zole are dissolved in 10 m) dry dichloromethane. 7.5 g (45 mmol) freshly distilled methyl trifluoromethanesulfonate are added. After a few min this exothermic reaction produces crystals, which are collected by filtration, washed with diethyl ether, and dried. The pale yellow powder is dissolved in 100 ml acetone. Diethyl ether is added, until the solution becomes turbid. Colorless plates separate upon cooling the turbid solution yield 87% m.p. 160-162°. 

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