SYNTHESIS OF 2-TRIFLUOROACETONYL-3-ALKYL/ALKOXY- CHROMONES AND THEIR REACTIONS WITH 1,2-BIDENTATE NUCLEOPHILES

The reaction of 3-substituted 2-methyl/2-benzyl/2-(2-phenethyl)chromones with trifluoroacetic anhydride in presence of potassium trifluoroacetate was investigated. It was established that the nature of substituent in position 3 of chromone ring has no crucial influence/limitation on this reaction, whereas only in the case of 2-benzyl substituent (in addition to 2 -sec-alkyl group) no reaction was occurred at all. Reaction of synthesized 2-(3,3,3-trifluoro-2-oxopropyl)chromones with hydrazine dihydrochloride afforded 3-(2-hydroxyphenacyl)-5-trifluoromethylpyrazoles, but reaction with hydroxylamine led to oximation of side-chain carbonyl group. Reaction of 2-trifluoromethylchromones with 1,2-bidentate nucleophiles led to substituted 2-hydroxyphenylpyrazoles and isoxazoles. Mechanisms of these ring-transformation reactions are discussed.