(Beta)-Aroylacrylic acid (I) react with 1,3-disubstituted-2-pyrazolin-5-ones in dry benzene to give (beta)-aroyl-(alpha-[4(1,3-disubstituted-2-pyrazolin-5-one)] propionic acids (II). Esterification of IId with diazomethane gives the corresponding methyl ester (III). Reactions of II with hydrazine hydrate and phenylhydrazine afford the corresponding 4-pyrazolinonyl-pyridazinones (V and VI). Dehydration of II yield the butenolides (VII), which undergo ring opening reaction with amines to give the (beta)-substituted (alpha) aroylpropionic acid N-alkylamides (VIII). Reactions of 4-pyrazolinonyl-pyridazinones (V) with anisaldehyde, ethyl bromoacetate, diethylsulfate, Grignard reagents have also been described. The in vitro antibacterial screening reveals substantial activities against Gram-positive and Gram-negative bacteria for compounds IIc and IId; while compounds IIb and Vb are inactive.
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