5- dibenzothiophenium triflate

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)dibenzothiophenium triflates are powerful electrophilic trinuoromethylating agents. The formation of 2 from the precursor I occurs readily.4... 

The [Ni (K -Tp)(aryl)(CF3)2] species can be prepared under mild conditions via the oxidation of Ni precursors [Ni (K -Tp)(aryl)(CF3)] and [Ni (K -Tp)(CF3)2] with S-(trifluoromethyl)-dibenzothiophenium triflate as weU as with diaryUodonium and aryl diazonium reagents, respectively. The Ni intermediates undergo aryl—CF3 bond-forming reductive eUmination (Scheme 67). Reaction of [Ni (K -Tp) (CH2CMe2-o-C6H4)] with a CF3 oxidant gives [Ni (K -Tp)... 

Related Reagents. trifluoromethylcopper(I) trifluoroiodo-methane (trifluoromethyl)dibenzothiophenium triflate and tetrafluoroborate (trifluoromethyl)dibenzoselenophenium triflate and tetrafluoroborate. 

As described previously for trifluoromethyl ethers, Umemoto [23c] reported on the trifluoromethylation of thiols with -(trifluoromethyl) dibenzothiophenium triflate affording the corresponding trifluoromethyl thioethers in medium to good yield. Otherwise, trifluoromethyl phenyl thioethers and ring-substituted analogs are readily made from iodo- or bromoarenes, methyl difluoro(fluorosulfonyl)acetate and elemental sulphur in the presence of cuprous iodide in hexamethylphosphoric triamide (HMPA) or A-methylpyrrohdone (NMP) (Scheme 10). 

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 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).

---