HALOACETYLATED ENOL ETHERS .7. SYNTHESIS OF 3-ARYL-5-TRIHALOMETHYLISOXAZOLES AND YL-5-HYDROXY-5-TRIHALOMETHYL-4,5-DIHYDROISOXAZOLES

beta-Aryl-beta-methoxyvinyl trihalomethyl ketones 1a-g, 2a-g [aryl = p -YC6H4 where Y=H, Me, OMe, F, Cl, Br, NO2] are cyclocondensed with hyd roxylamine hydrochloride to afford the yl-5-hydroxy-5-trihalomethyl-4, 5-dihydroisoxazoles 3a-g, 4a-f in good yield. The dehydratation of com pounds 3a-g with concentrated sulfuric acid, led the corresponding 3-a ryl-5-trichloromethylisoxazoles 5a-g. An alternative one-pot procedure yields 3-aryl-5-trihalomethylisoxazoles 5,6a-g directly by cycloconde sation of 1,2a-g with hydroxylamine hydrochloride in the presence of a n excess of concentrated hydrochloric acid.