Behavior of 3‐benzylamino‐5‐aryl‐2(3 H )‐furanones towards some nitrogen nucleophiles

Ring closure of 2‐ N ‐benzylamino‐3‐aroylpropionic acids ( 3 ) with acetic anhydride afforded 3‐ N ‐benzylamino‐5‐aryl‐2(3 H )‐furanones ( 4 ). The reaction of the furanones ( 4 ) with benzylamine in benzene was found to be time dependent. Thus refluxing the reaction mixture for 1 h only afforded the open‐chain amides ( 5a‐c ). When the reaction was conducted for 3 h the 2(3 H )‐pyrrolones ( 6 ) were obtained. Hydrazine hydrate affected ring opening of the furanones to give the hydrazides ( 5d‐f ). Also, semicarbazide converted ( 4 ) into the corresponding semicarbazide derivatives ( 5g‐i ). The hydrazides ( 5d‐f ) were reacted with benzoyl chloride to give the corresponding diaroylhydrazines ( 5j‐l ). The open‐chain derivatives ( 5 ) were converted into a variety of heterocycles: isothiazolones ( 7 ), dihydropyridazinones ( 8 ), 1,3,4‐oxadiazoles ( 9 ) and 1,2,4‐triazole derivatives ( 10 ) via cyclization reactions.