Abstract The present review focuses on dibenzo [b, f] oxepin-10 (11H)-one (I, X= O) and dibenzo [b, f] thiepin-10 (11H)-one (I, X= S) as common synthons in the efficient synthesis of various dibenzoxepino [4, 5-and dibenzothiepino [4, 5]-fused five-membered heterocycles:[2, 3] fused thiophene (II),[3, 4] fused thiophene (III), furan (IV), pyrrole (V), imidazole (VI), pyrazole (VII), oxazole (VIII), and thiazole (IX). The potential of I to be ...