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.