Synthesis of (e)-1-(5-chloro-2-hydroxy-4-methylphenyl)-3-(4-bromophenyl)prop-2-en-1-one and 4-chloro-5-methyl-2-(5-(4-bromophenyl)-4,5-dihydro-1H-pyrazol-3-yl)phenol and its derivatives

Abstract

In continuation of earlier work, the simple and efficient protocol was adopted to synthesize bromo-pyrazoline derivatives. The synthetic protocol instigates with acetylation of properly substituted phenol 1a, subsequently, Fries migration was performed to afford substituted acetophenone 2a. The product 2a was then treated with appropriately substituted aromatic aldehyde to afford the corresponding chalcone 3a. The chalcone 3a was then reacted with hydrazine hydrate to provide 1H-pyrazoline 4a and its derivatives 4b-d using acetylation, benzoylation and nitrosoation in moderate to high yields. The structures of the intermediate 1a, 2a, 3a, and pyrazolines 4a-d were established using chemical reactivity, elemental and spectral analyses.