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‐1 H ‐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‐1 H ‐pyrazolo‐4‐ylmethylene)‐2‐phenyl‐4 H ‐oxazol‐5‐one ( 5 ), 5‐azido‐1‐phenyl‐3‐pyridin‐4‐yl‐1 H ‐pyrazol‐4‐carbaldehyde ( 8 ) and 1‐aryl‐3‐(5‐chloro‐1‐phenyl‐3‐pyridin‐4‐yl‐1 H ‐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.