Synthesis and reactions of some novel 4-biphenyl-4- (2H)-phthalazin-1-one derivatives with an expected antimicrobial activity

Abstract In this study reaction of 1-(biphenyl-4-carbonyl)benzoic acid ( 1 ) with hydrazine hydrate, phenyl hydrazine, acetyl hydrazine and benzoyl hydrazine in boiling dry benzene gave the corresponding 4-biphenyl-4-yl-( 2H )-phthalazin-1-one ( 2a–d ), respectively. The structure of 2c was established via its reaction with 2-chlorobenzaldehyde, 2-nitrobenzaldehyde in ethanol to give the chalcones 3a,b , respectively. On the other hand, the cyclocondensation of the acid 1 with semicarbazide and thiosemicarbazide in sodium acetate gave phthalazinone amide/thioamide 4a,b , respectively. The reaction of 1 with hydroxyl amine hydrochloride in different media was also studied, to give the oxime derivative 5, which was readily converted to benzooxazin-1-one derivative 6 by boiling in acetic anhydride. Compound 6 was also obtained, when the acid 1 was reacted with hydroxyl amine hydrochloride in boiling pyridine. In addition, the phthalazinone derivative 2a reacted under Mannich reaction condition with phthalimide, morpholine, o -crezole and β-naphthol to give Mannich bases 7a–d , respectively. The structural assignment of the new compounds was based on analytical and spectral data. And some of the new products showed antimicrobial activity.