Synthesis of 5,6-Dihydro-2-trifluoromethyl-1,4-doxin-3-carboxanilides through Polymer-bound Activated Ester:Construction of Dihydro-1,4-dioxin

摘要

A new construction of dihydro-1,4-dioxin and a synthesis of 5,6-dihydro-2-trifluoromethyl-1,4-dioxin-3-carboxanilides 22 through polymer-bound activated ester are described. An intermediate #beta#-hydroxy ether 18 was prepared from the substution reaction of #alpha#-chloro compound 8 with ethylene glycol followed by treatment with Raney Ni. Replacement of hydroxy by chlorine and then dehycrochlorination afforded trifluoromethyl dihydro-1,4-dioxin ester 15. The polymer-bound trifluoromethyl dihydro-1,4-dioxin-3-carboxylic acid, 4-hydroxy-3-nitrobenzophenone ester (21)was prepared through the reaction of polystyrene-bound 4-hydroxy-3-nitrobenzophenone(19)with the trifuoromethyl dihydro-1,4-dioxin-3-carbonyl chloride(20). Refluxing of 21 with substituted aniline in acetonitrile gave the corresponding carboxanilide 22. The reaction rate depended on the nucleophilicity of nitrogen of the aniline.