Synthesis of some new 1,2,3-selenadiazolo[4', 5':5,4]cyclopent[b]indoles and 6,11-dihydro-5-methylquinolino-[2', 3':5,4]cyclopent[b]indoles

Reaction of 1-oxo-1,2,3,8-tetrahydrocyclopent[b]indoles 1a-e with semicarbazide hydrochloride produced 1-semicarbazono-1,2,3,8-tetrahydrocyclopent[b]indoles 2a.e, which are subjected to oxidative cyclisation using seleniumdioxide to afford the novel 4,8-dihydro-1,2,3-selenadiazolo[4',5':5,4]cyclopent[b]indoles 3a-e. The same compounds la-e on treatment with o-aminoacetophenone 4 in glacial acetic acid furnished 12-methyl-6-(1'-propen-2'-ol)-dibenzo[b,f][1,5]diazocine 5 as a common product in all the cases along with 6,11-dihydro-5-methylquinolino[2',3';5,4]cyclopent[b]indoles 6a-e. A plausible mechanism for the formation of the products 5 and 6 has been proposed.