New synthesis on the basis 2-allyloxy chalcone and NMR studies its some derivatives.

Synthesis and NMR investigations of cyclohexenone, flavanone, isoxazol and indazole derivatives of (2E)-3-[2-(allyloxy)-5-bromophenyl]-1-(2-hydroxy-5-methylphenyl)-2-propen-1-one (I, chalcone) have been carried out. The results confirm the formation of O-H•••O type intramolecular hydrogen bond and intramolecular cyclization in the (2E)-3-[2-(allyloxy)-5-bromophenyl]-1-(2-hydroxy-5-methylphenyl)-2-propen-1-one (I), the presence of conformational and keto-enol tautomeric transitions in the 6-acetyl-5-[2-(allyloxy)-5-bromophenyl]-3-(2-hydroxy-5-methylphenyl)-2-cyclohexen-1-one (II), conformational transitions in the 2-{4-[2-(allyloxy)-5-bromophenyl]-3-methyl-4.5-dihydro-1.2-benzisoxazol-6-yl}-4-methylphenol (III) and 2-{4-[2-(allyloxy)-5-bromophenyl]-3-methyl-4.5-dihydro-1H-indazol-6-yl}-4-methylphenol (IV). The conformational and keto-enol tautomerism in the investigated compounds have been also confirmed by chemical methods.