Studies on the reaction of N ‐(3‐carbethoxy‐4,5,6,7‐tetrahydrobenzo[ b ]thien‐2‐yl)‐ N ′‐phenylthiourea with hydrazine hydrate (Part 1)

The reaction of N ‐(3‐carbethoxy‐4,5,6,7‐tetrahydrobenzo[ b ]thien‐2‐yl)‐ N ′‐phenylthiourea ( 1 ) with hydrazine hydrate in 1‐butanol afforded a mixture of compounds 2, 3 and 4 . Treatment of 3 and 4 with nitrous acid gave 6 and 8 respectively, while reactions of 3 with acetylacetone gave 7 . Synthesis of tetracyclic compounds 9a‐f and 11 from the reactions of 3 with ethyl orthoformate or appropriate acids, acid chloride, carbon disulphide and/or ethyl chloroformate. Also its reaction with isothiocyanate derivatives gave the corresponding thiosemicarbzides 12a,b which on, refluxing in alcoholic KOH gave the unexpected tetracyclic products 14a,b . Similarly the tetracyclic compounds 16a‐e and 19 were obtained by cyclization of 4 and 18 respectively.