[Cl:1][C:2]1[CH:18]=[C:17]([C:19]([F:22])([F:21])[F:20])[CH:16]=[CH:15][C:3]=1[O:4][C:5]1[CH:14]=[CH:13][C:8]2=[N+:9]([O-])[O:10][N:11]=[C:7]2[CH:6]=1.P(OCC)(OCC)OCC>C(O)C>[Cl:1][C:2]1[CH:18]=[C:17]([C:19]([F:22])([F:20])[F:21])[CH:16]=[CH:15][C:3]=1[O:4][C:5]1[CH:14]=[CH:13][C:8]2=[N:9][O:10][N:11]=[C:7]2[CH:6]=1A mixture of 5-(2-chloro-4-trifluoromethylphenoxy)benzo-2,1,3-oxadiazole N-oxide (2.0 g) and triethyl phosphite (10 ml) is heated under reflux in ~150 ml of ethanol for 4 hours. The reaction is cooled and stripped, and the crude product is purified by prep. TLC (15% ethyl acetate/hexane) to give 5-(2-chloro-4-trifluoromethylphenoxy)benzo-2,1,3-oxadiazole, m.p. 65°-66°.
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