Action of primary aliphatic and aromatic amines on 2,4-dihydro-5-methyl-2-phenyl-4-benzylidene-3H-pyrazol-3-one

5-Methyl-2-phenyl-4-benzylidenepyrazol-3-one (1) reacted with primary aliphatic amines such as n-butylamine, benzylamine, ethylenediamine or ethanolamine in ethanol at room temperature to give the pyrazolidinone pyrazolyl amine derivative (2). However, when (1) was refluxed in ethanol with primary aromatic amines such as p-toluidine, p-anisidine or 2-aminopyridine, it afforded phenylmethylidene bis(hydroxypyrazole) derivative (3). Treatment of (1) with 1,2-diaminobenzene or 2,3-diaminopyridine in refluxing n-butanol yielded the imidazole derivatives (4a and b) together with the 1,5-benzodiazepine derivative (5a) and 2-pyrazolylamino-3-benzylideneaminopyridine derivative (6), respectively. On the other hand, similar treatment of (1) with 1,4-diaminobenzene or 2-amino-3-hydroxypyridine gave 1,4-phenylene bis(pyrazolyl, benzyl amine) derivative (7) or 3-alkoxy derivative of 2-aminopyridine (8), respectively. The structures of all the products are based on analytical, chemical and spectroscopic evidence.