Trifluoromethyl triflate

All the S-, Se-, and Te-(perfluoroalkyl)dibenzothiophenium, -selenophenium, and -tellurophenium salts synthesized above are stable crystalline materials at room temperature. Their melting or decomposition points (dec. p) are higher than 100°C. Nitro substituents decrease their stability [S-salt 17 mp 155°C > dinitro S-salt 39 dec. p 130-135°C]. The chalcogen stability increases in the order S < Se < Te [dec. p S-salt 39 130-135°C < Se-salt 40 198-200°C < Te-salt 41 275-280°C]. Thermolysis of S-salt 17 at 200 C gave trifluoromethyl triflate (50) and dibenzothiophene (51) in high yields (Eq. 12). Thermolysis of dinitro S-salt 39 at 140°C gave 50 and dinitrodiben-zothiophene 52 (Eq. 13). 

The 3 -trifluoromethyldibenzothiophenium salts are stable solids. Thermolysis leads to dibenzothiophene and trifluoromethyl triflate. Alkaline hydrolysis leads to the 3 -oxide (Equation 111). 

An example of cleavage ot the sulfur-oxygen bond in trifluoromethane-sulfonic ester has been reported Trifluoromethyl triflate reacts with neutral or anionic nucleophiles with elimination of carbonyl difluonde and formation of trifluoromethanesulfonyl fluoride [57] (equation 37) The mechanism of this reaction involves elimination of fluoride ion, which is a chain earner in the substitution of fluorine for the trifluoromethoxy group... 

Glycosyl phosphites, activated by catalytic amounts of trifluoromethyl triflate, are also glycosyl donors with oxygen leaving groups. 

Taylor and Martin have summarized the synthesis of trifluoromethyl triflate (TFMT)98 in equations 65-71. We discuss here only the last three methods in more detail. By utilizing... 

Reaction with P2O5. Trifluoromethanesulfonic acid (TfOH) reacts with an excess of Phosphorus(V) Oxide to give Trifluoromethanesulfonic Anhydride (eq 1), while treatment with a smaller amount of P2O5 (Tf0H P205 = 6 1) and slower distillation leads to trifluoromethyl triflate (eq 2)f... 

The synthetic utility of trifluoromethyl triflate as a trifluoro-methanesulfonylating agent is severely limited, because the reagent is rapidly destroyed by a fluoride-ion chain reaction in the presence of other nucleophiles. ... 

The reaction of Tf20 with a catalytic amount of Anti-mony(V)Fluoride at 25 °C produces trifluoromethyl triflate in... 

Marrec et al. [34] used trifluoromethyl triflate (TFMT) as a generator of trifluoro-methoxy anion when activated by fluoride anions. Commercially available flnorides (silver fluoride and n-tetrabutylammonium triphenyldifluorosihcate), combined with TFMT, allow a simple generation, in situ, of silver and n-tetrabntylammoninm trifluoromethoxides which were able to react with electrophihc snbstrates. Silver trifluoromethoxide, which is usually more efficient than n-tetrabntylammoninm trifluoromethoxide, converts, under mild conditions, primary ahphatic bromides and iodides as well as primary and secondary benzylic or allylic bromides. Several trifluoromethyl ethers, which could be valuable building-blocks, were prepared in such a way (Scheme 7). 

Marrec O, Billiard T, Vors J-P, Pazenok S, Langlois BR (2010) A deeper insight into direct trifluoromethoxylation with trifluoromethyl triflate. J Fluorine Chem 131 200-207. doi 10.1016/j. fluchem.2009.11.006... 

Under SbFs catalysis, Trifluoromethanesulfomc Anhydride is readily decomposed to trifluoromethyl triflate in high yield (eq 25). This method is the most convenient procedure reported for preparation of the triflate. 

When the reaction between a-trifluoromethyl sulfone 286 and paraformaldehyde was carried out in the presence of potassium carbonate, the vinyl sulfone was obtained quantitatively upon elimination of triflate anion368. Such a deacylative methylenation was observed in the reaction between /J-ketosulfones 287 and 288 and paraformaldehyde3 69 3 71. 

The indium-mediated allylation of trifluoroacetaldehyde hydrate (R = H) or trifluoroacetaldehyde ethyl hemiacetal (R = Et) with an allyl bromide in water yielded a-trifluoromethylated alcohols (Eq. 8.56).135 Lanthanide triflate-promoted indium-mediated allylation of aminoaldehyde in aqueous media generated (i-airiinoalcohols stereoselectively.136 Indium-mediated intramolecular carbocyclization in aqueous media generated fused a-methylene-y-butyrolactones (Eq. 8.57).137 Forsythe and co-workers applied the indium-mediated allylation in the synthesis of an advanced intermediate for azaspiracids (Eq. 8.58).138 Other potentially reactive functionalities such as azide, enone, and ketone did not compete with aldehyde for the reaction with the in situ-generated organo-indium intermediate. 

A highly fluorinated bis(pyrazolyl)borate ligand, dihydridobis(3,5-bis(trifluoromethyl)pyrazo-lyl)borate has been synthesized. The zinc triflate complex was prepared from the potassium salt of the ligand and exhibits distorted tetrahedral coordination which allows comparison of the amount of distortion, in relation to the electronic properties of substituents, with the methylated analog.165... 

After extensive experimentation, a simple solution for avoiding catalyst deactivation was discovered, when testing an Ir-PHOX catalyst with tetrakis[3,5-bis (trifluoromethyl)phenyl]borate (BArp ) as counterion [5]. Iridium complexes with this bulky, apolar, and extremely weakly coordinating anion [18] did not suffer from deactivation, and full conversion could be routinely obtained with catalyst loadings as low as 0.02 mol% [19]. In addition, the BArp salts proved to be much less sensitive to moisture than the corresponding hexafluorophosphates. Tetrakis (pentafluorophenyl)borate and tetrakis(perfluoro-tert-butoxy)aluminate were equally effective with very high turnover frequency, whereas catalysts with hexafluorophosphate and tetrafluoroborate gave only low conversion while reactions with triflate were completely ineffective (Fig. 1). 

S-(Trifluoromethyl)diphenyIsulfonium triflate (29) and S -(trifluoro-methyl)phenoxathiinium triflate (32) were synthesized as shown in Eqs. 5 and 6. 

The F CFs chemical shifts of each of the 5- and 5e-(trifluoromethyl)di-benzothiophenium and -selenophenium triflates were linearly correlated with Hammett s substituent constants Op or Om, as evident from Fig. 1. This indicated that the electron density of the trifluoromethyl group is linearly correlated with the electronic nature of the substituents attached to the dibenzoheterocyclic salts. These F CF3 chemical shifts are in good agreement with the order of trifluoromethylating power, as discussed below. 

The trifluoromethylating order of reactivity of a series of 5-, Se-, and Te-(trifluoromethyl)dibenzothiophenium, -selenophenium, and -telluro-phenium triflates was determined by relative reaction rates with aniline. 

Fig. 1. Relationship between F CF3 chemical shifts of S-, Se-, and 7e-(trifluoromethyl)-dibenzothiophenium, -selenophenium, and -tellurophenium triflates and Hammett s constants Om or (Tp for the ring substituents S, Se, and Te refer to substituted and unsubstituted S-, Se-, and Te-(trifluoromethyl)dibenzothiophenium, -selenophenium, and -tellurophenium triflates, respectively. The numbers on the lines are the compound numbers shown in the text. Substituents and their substitution positions are shown in the parentheses. The smaller the F NMR chemical shift is, the more downfield is the resonance (CFCI3 served as an internal standard in CD3CN).

Sodium salts of )3-diketones or j8-keto esters were trifluoromethylated with 5-triflate 17 or 5-sulfonate 42 in good yields (Eqs. 18,19). The sodium... 

Lithium phenylacetylide was trifluoromethylated with the less powerful Se-triflate 26 in high yield (Eq. 20). 

Treatment of the most powerful dinitro 5-salt 39 with triphenylphosphine gave (trifluoromethyl)triphenylphosphonium triflate in good yield (Eq. 31). However, moderately powerful 5-salt 17 did not produce the phosphonium triflate even at an elevated temperature. 

Kinetic Parameters for the Trifluoromethylation of Aniline with 5-(Trifluoromethyl)dibenzothiophenium Triflate (17), S-(Trifluoromethyl)diphenylsulfonium Triflate (29), AND 5-(Trifluoromethyl)-3,7-DINITRODIBENZOTHIOPHENIUM TrIFLATE (39) IN DMF-d7 AT 25°C... 

Trifluoromethyl [ F]hypofluorite Acetyl [ F]hypofluorite Perchloryl f Flfluoride Xenon d/[ F]fluoride 1-[ F]Fluoro-2-pyridone AZ-f FlFluoropyridinium triflate A/-[ F]Fluoro-A/-alkylsulphonamides Bromo [ F]fluoride... 

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