New Synthetic Method of Azuleno[1,2-c]thiophenes

On the viewpoints of physical and chemical properties and biological activities, syntheses of a variety of heterocycle-fused azulenes have been repoted.[1] Of them, thiophene-fused azulenes were prepared by using different types of stating materials as follows. Azuleno[2,1-b] thiophenes are readily obtained from the reactions of 2-chloroazulene derivatives with ethyl mercaptoacetate in a few steps in good yield by Matsui[2] and Yamane.[3] On the other hand, the first synthesis of azuleno[1,2-c]thiophenes was accomplished by the reaction of 3-methoxycarbonyl-2H-cyclohepta[b]furan2-one with morpholino enamine of 3-oxotetrahydro-thiophene followed by dehydrogenation in poor yield by Fujimori.……