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. Copyright © 2014 John Wiley & Sons, Ltd.