Synthesis of 2-trifluoromethyl-2-hydroxy-2H-chromenes via cyclization of (Z)-trifluoromethyl alkenyl triflates and salicylaldehydes

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A new and efficient method for the synthesis of 2-trifluoromethyl-2-hydroxy-2H-chromenes was developed via intermolecular cyclization of (Z)-trifluoromethyl alkenyl triflates and salicylaldehydes. A series of 2-trifluoromethyl-2-hydroxy-2H-chromenes with aryl or alkyl groups at 3-position have been obtained in moderate to excellent yields. And a key intermediate, 3-phenyl-4-(pyrrolidin-1-yl)-2-(trifluoromethyl)chroman-2-ol (6), was isolated and fully characterized, which suggests that the elimination of pyrrolidine from this intermediate is the last step during the formation of 2-trifluoromethyl-2-hydroxy-2H-chromenes.