Transition metal-free controlled synthesis of bis[(trifluoromethyl)sulfonyl]ethyl-decorated heterocycles

Abstract

Several heterocycles reacted with shelf-stable 2-(2-fluoropyridinium-1-yl)-1,1-bis[(trifluoromethyl)sulfonyl] ethan-1-ide, a latent Tf₂CCH₂ source, to give rise in a mild and controllable way to adducts via direct C–H bis[(trifluoromethyl)sulfonyl]ethylation reactions. This metal- and irradiation-free protocol is convenient. Besides, the volatile side-product 2-fluoropyridine can be smoothly eliminated under vacuum, which facilitates purification. The substrate scope survey discloses that exquisite chemo- and regioselectivities are achieved in a variety of heterocyclic systems. Of particular interest are the late-stage structural modification of known pharmaceuticals, such as the marketed drugs Phenazone (Antipyrine) and Edaravone, and the development of a water soluble fluorescent dye.