MICROWAVE-ASSISTED SYNTHESIS OF 1,3,4 –OXADIAZOLES CONTAINING PYRAZOLONES Mikrowellen-unterstützte Synthese von 1,3,4-Oxadiazole ENTHALTEN Pyrazolone

The key intermediate acetohydrazide 6 cyclization with aryl substituted acids 7 a-g in presence of phosphorous oxy chloride (POCl3) under microwave irradiation resulted in the formation of the 2-(5-oxo-4-(2-phenylhydrazono)-3-(trichloromethyl)-4,5-dihydro-1H-pyrazol-1- yl)-N-(1-(5-phenyl-2,3-dihydro-1,3,4-oxadiazol-2-yl)ethyl)acetamide (8a-h) in excellent yields, also under microwave irradiation and in the presence of dry phosphorous oxy chloride as cyclizing agent. The results obtained indicate that, unlike classical heating, microwave irradiation results in higher yields, shorter reaction times (5-15 min.) and cleaner reactions.