A Convenient Synthesis of Some Pyrazolinone and Pyrazole Derivatives

A convenient synthesis of some novel 6-amino-4-aryl-1-phenyl-3-pyridin-4-yl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles (3a,b) and 5-chloro-1-phenyl-3-pyridin-4-yl-1H-pyrazole-4-carbaldehyde (4) is described. Compound 4 was obtained by the reaction of 2-phenyl-5-pyridin-4-yl-2,4-dihydropyrazol-3-one (1) with dimethylformamide and phosphorus oxychloride under Vilsmeier-Haack reaction conditions. Compound 4 was subjected to react with different reagents such as hippuric acid, sodium azide and aromatic ketones to afford 4-(5-chloro-1-phenyl-3-pyridin-4-yl-1H-pyrazolo-4-ylmethylene)-2-phenyl-4H-oxazol-5-one (5), 5-azido-1-phenyl-3-pyridin-4-yl-1H-pyrazol-4-carbaldehyde (8) and 1-aryl-3-(5-chloro-1-phenyl-3-pyridin-4-yl-1H-pyrazol-4-yl)propenones (12a,b), respectively. The latter compounds were also prepared via Michael reaction by treatment of compound 1 with some different chalcones.