5-amino-1,2-dihydropyrazol-3-one

Toluene (500mL), triethylamine (138.6mL, 1.0mol, 2.0eq) and the step (1) to give 5-hydroxy-4-carboxylate (64g, 0.5mol, 1.0eq) added to the reaction flask, the temperature of the system was raised to 80 .5 times added diphenylphosphoryl azide (DPPA, 162.5mL, 0.75mol, 1.5eq .), Stirred at this temperature for 5 hours, cooled to room temperature.The reaction solution was concentrated, a saturated aqueous ammonium chloride solution was added 500 mL, the precipitated white precipitate was collected and dried to give 5-amino-1, 2-dihydro-pyrazol-3-one 44.7 g (90percent yield)General procedure: A mixture of chalcone 4 (0.20 gm, 1 mmol) and the appropriateheterocyclic amine 5, 6, 7, 8 and 9 (1.2 mmol) in DMF (10 ml) in thepresence (26 mg, 0.1 mmol) of KOH was refluxed for 0.45-2 h at110 C. The reaction monitored through TLC (petroleum ether: ethylacetate 8:2, Rf: 0.2, 0.3, 0.25, 0.3, 0.25, respectively), reaction mixturewas allowed to cool to ambient temperature, then poured into ice-waterand the solid product was collected by filtration followed by washingwith ethanol. The crude product was then recrystallized from appropriatesolvent to give pure products 10, 11, 12, 13 and 15, respectively.