Addition reactions of heterocyclic compounds. Part 75. Reactions of dimethyl acetylenedicarboxylate with some N-methylindoles
Abstract
4-Methyl-1,2,3,4-tetrahydrocyclopent[b]indole,5-methyl-1,2,3,4-tetrahydrocarbazole, and 5-methyl-5,6,7,8,9,10-hexahydrocyclohept[b]indole were treated with dimethyl acetylenedicarboxylate in aqueous solvents. Lactones derived from the 2,3-dihydroindole system were obtained in all cases, and a diketone possessing the phenanthridone nucleus was also obtained from the carbazole. The products were identified from 1H and 13C n.m.r. spectral comparisons, and in some cases from 13C–1H coupling constants observed in the 13C spectra.