A new version of Umemoto’s reagents: A three-step one-pot preparation of 2,3,7,8-tetrafluoro-S-(trifluoromethyl)dibenzothiophenium triflate [1]

•A new one-pot method was developed for practical preparation of powerful 2,3,7,8-tetrafluoro-S-CF3-dibenzothiophenium triflate 2.•The one-pot method comprised of 3 steps; (1) CF3SO2Na, (CF3CO)2O, CF3COOH, (2) tetrafluorobiphenyl, TfOH, and (3) H2O2.•The CF3S by-product formed in step 2 was completely converted to the final product 2 in the step 3.•The powerful reagent 2 was easily isolated in a good yield by simple water-washing method.•The reaction mechanism including the formation of the CF3S by-product was proposed.