Synthesis of Pyrazoles via Vilsmeier Haack reaction and their pyrazolone, thiazolidinedione derivatives: A comparative study of conventional and microwave routes

Phenyl hydrazine treated with variable acetophenone to give substituted phenyl carbonyl hydrazone compounds, 1- (1-substituted -2-ylethylidene)-2-phenylhydrazine (1a-e). This is undergoing cyclization by using Vilsmeier-Haack reaction and afforded compounds 3-substituted-2-yl-1-phenyl-1H-pyrazole-4-carbaldehyde (2a-e). The reaction of an N,N disubstituted formamide, such as DMF or N-methylformanilide, with acid chlorides, such as phosphoryl chloride or phosgene, leads to the formation of an adduct, this adduct usually referred to as a Vilsmeier Haack reagent. In one path compound 2a-e reflux with pyrazolone and give compound 4-((3-substituted -2-yl-1-phenyl-1H-pyrazol-4-yl)methylidene)-5-methyl-2,4-dihydro-3H- pyrazol-3-one (3a-e), in another pathway compounds 2(a-e) react with thiazolidione and give target molecule compounds 5- {(3-(4-substitutedphenyl)-1-phenyl-1H-pyrazol-4-yl)methylidene}-1,3-thiazolidine-2,4-dione (4a-e). The structures of all the synthesized compounds were supported by spectral and analytical studies.