Synthesis of 5,6-dihydro-2-trifluoromethyl-1,4-dioxin-3-carboxanilides through polymer-bound activated ester: Construction of dihydro-1,4-dioxin

A new construction of dihydro-1,4-dioxin and a synthesis of 5,6-dihydro-2-t rifluoromethyl-1,4-dioxin-3-carboxanilides 22 through polymer-bound activat ed ester are described. An intermediate beta-hydroxy ether 18 was prepared from the substitution reaction of alpha-thio-alpha-chloro compound 8 with e thylene glycol followed by treatment with Raney Ni. Replacement of hydroxy by chlorine and then dehydrochlorination 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 thro ugh the reaction of polystyrene-bound 4-hydroxy-3-nitrobenzophenone (19) wi th the trifluoromethyl dihydro-2,4-dioxin-3-carbonyl chloride (20). Refluxi ng of 21 with substituted aniline in acetonitrile gave the corresponding ca rboxanilide 22. The reaction rate depended on the nucleophilicity of nitrog en of the aniline.