Addition reactions of heterocyclic compounds. Part 78. Reaction of dimethyl acetylenedicarboxylate with some cyclopent[b]indoles and cyclohex[b]indoles and the crystal structure of (Z)-methyl 1-methoxycarbonylmethyl-11-methoxycarbonylmethylene-12-oxo-1,1a,1b,2,3,4,4a,8,9,9a-decahydro-1b,4a-epoxyethanoindolizino-[2,3,4,5,6-jklm]carbazole-1-carboxylate

Abstract

Reaction of 5,6,9,10-tetrahydro-4H,8H-cyclopenta[4,5]pyrrolo[3,2,1-ij]quinoline and 5,6,8,9,10,11-hexahydro-4H-pyrido[3,2,1-jk]carbazole with dimethyl acetylenedicarboxylate in aqueous methanol or acetic acid gave five new lactones and a phenanthridone diketone. In aqueous methanol and acetonitrile, the carbazole gave three closely related (1 + 2 DMAD – CH₂) adducts of a type not previously encountered. The structure of one of these was established by X-ray crystallography; their formation, which includes C-alkylation of a CH₂N group, is discussed. The cyclopentene, and also its N-methyl analogue, yielded a new type of (1 + DMAD + H₂O) adduct possessing a 1-benzazocin-2-one system. A novel (1 + 3 DMAD) adduct was also isolated. All the products were indentified from[¹H and ¹³C n.m.r. spectral comparisons, and in some cases from ¹³C–¹H coupling constants observed in the ¹³C n.m.r. spectra.