Azidation of aminothiophene derivative 1 afforded the corresponding azido derivative 2.The latter reacted with triphenylphosphine to afford iminophosphorane derivatives 3.Reacting 3 with phenylisocyanate gave the highly reactive carbodiimide intermediate 4,which was reacted with different nitrones to afford new l,2,4-oxadiazolidin-5-ylidene-aminothiophenes 5a-c. Treatment of 4 with absolute EtOH at room temperature gave methyleneamino-5-(methylthio)thiophene 7,(methylthio)-3-(3- phenylureidothiophene)-2-carboxylate 8 or thienopyrimidine 9 and 10 at refluxing temperature.Finally reaction of carbodiimide intermediate 4 with different secondary amines gave the new thienopyrimidines 11a-c. Azidation of aminothiophene derivative 1 afforded the corresponding azido derivative 2. The latter reacted with triphenylphosphine to afford iminophosphorane derivatives 3. Reacting 3 with phenylisocyanate gave the highly reactive carbodiimide intermediate 4, which was reacted with different nitrones to afford new l, 2,4- oxadiazolidin-5-ylidene-aminothiophenes 5a-c. Treatment of 4 with absolute EtOH at room temperature gave methyleneamino-5- (methylthio) thiophene 7, (methylthio) -3- (3- phenylureidothiophene) -2-carboxylate 8 or thienopyrimidine 9 and 10 at refluxing temperature .Finally reaction of carbodiimide intermediate 4 with different secondary amines gave the new thienopyrimidines 11a-c.