1,3-Dihydro-3,3-dimethyl-1-(trifluoromethyl)-1,2-benziodoxole, Tognis Reagent

Dry KOAc (6.66 g, 67.9 mmol, 1.68 equivalents) and iodine derivative (11.94 g) were stirred in anhydrous MeCN (100 mL) at ambient temperature for 1 hour. The mixture was filtered. The remaining white solid was washed with MeCN to give a clear, almost colorless solution. MeCN (100 mL) was added to the mixture. The solution was cooled to -17 °C.

Add Me3SiCF3 (9.16 mL, 61.97 mmol) to the mixture, followed by dropwise addition of a solution of tetrabutylammonium triphenyldifluorosilicate (0.065 g, 0.120 mmol) in MeCN (2 mL). Stir the reaction mixture at -17 °C for 16 hours. Heat the reaction mixture to -12 °C. At -12 °C, add Me3SiCF3 (1.31 mL, 8.9 mmol) to the reaction mixture. Warm the reaction mixture to room temperature over 3 hours. Stir the reaction mixture at room temperature for another 3 hours. Remove the volatile components of the mixture. Vacuum dry the residue. Add dry pentane (150 mL) to the remaining brown solid. Filter the resulting mixture through a dry alox pad. Evaporate the clear, colorless solution until dry. Vacuum dry the residue.

1,3-dihydro-3,3-dimethyl-1-(trifluoromethyl)-1,2-benziodoxole is in the form of colorless, white solid. It is soluble in all common organic solvents. It is used as effective and very versatile reagent for trifluoromethylation reactions of a variety of compounds including secondary and primary aryland alkylphospines, phenols, peptides containing cysteine residues by SPPS and electrophilic S-trifluoromethylation, arenes and N-heterocycles, and electrophilic N-trifluoromethylation of arozoles.

J. Charpentier, N. Früh, A. Togni, Electrophilic Trifluoromethylation by use of hypervalent iodine reagents, Chemical Reviews, 2015, vol. 115, pp. 650-682