SYNTHESIS, REACTIVITY AND APPLICATIONS OF SOME PYRIDYL PYRAZOLONE DERIVATIVES

Abstract

The Vilsmeier- Haack reaction of compound I gives 5-chloro-3-pyridyl-1-phenyl-

1H-pyrazole-4-carboxaldehyde D. Knoevenagel condensation of II with p-methyl acetophenone, and acetophenone gives 3-(5-chloro-3-pyridyl-1-phenyi-1H-pyrazol-4- yl)-1-phenyl/p-tolyl-prop-2-en-1-ones illa,b.

Furthermore, the structure of the prepared chalcones llla,b was confirmed by the following chemical reactions:

i) Condensation of llla,b with phenyl hydrazine in glacial acetic acid gives

4-(1,3-diphenyl/1-phenyl-3-p-tolyl-2-pyrazolin-5-yl)-5-chloro-3-pyridyl-l­

phenyl-1H-pyrazoles IVa,b,

ii) ii) Bromination of ma,b in carbon tetrachloride gives 2,3-dibromo-3-(5- chloro-1-phenyl-3-pyridyl-1H-pyrazol-4yl)-1-phenyl/p-tolylpropan-l-one Va,b, iii) iii) The reaction ofVa,b with phenylhydrazine in acetic acid gives 5-(5<hloro-1- phenyl-3-pyridyi-1-H-pyrazol-4-yl)-1-phenyl-3phenyVp-tolyi-IH-pyrazoles Vla,b.

And also, the nucleophilic substitution reactions of Compound II, was illustrated by the following:

i) With sodium ethoxide in boiling ethanol the corresponding 1-phenyl-3- pyridyl-5-ethoxypyrazolo-4-carboxaldehyde VII was obtained