Synthesis and structure of new trichloromethyl-β-diketones -: 5-Trichloromethylisoxazole and 5-isoxazolecarboxylic acid derivatives

An improved method for the synthesis of a new series of trichloromethyl-beta-diketones including 1,1,1-trichloropentan-2,4-dione (2a), 1,1,1-trichloro-3-methylhexan-2,4-dione (2b), 4,4,4-trichloro-1-phenylbutan-1,3-dione (2c), 4,4,4-trichloro-2-methyl-1-phenylbutan-1,3-dione (2d), 2-trichloroacetylcyclohexanone (2e), 4-tert-butylcyclohexanone (2f), 4-tert-butylcycloheptanone (2g), and 4-test-butylcyclooctanone (2h) is reported. A multinuclear NMR study showed that beta-dicarbonyl compounds 2b and 2d-2h are predominantly in the keto form and 2a and 2c are in the enol form. The trichloromethyl-beta-diketones react with hydroxylamine hydrochloride leading to three sets of isoxazole derivatives.