Indole as a Dienophile in Inverse Electron Demand Diels-Alder Reactions: Reactions with 1,2,4-Triazines and 1,2-Diazines

Article abstract of DOI:10.1021/jo00297a050

Indole reacts with 1,2,4-triazines in the absence of solvent or in the presence of limited amounts of solvent to produce β- or γ-carbolines, benzo<1,7>naphthyridines, or the noncyclized 3-<5-(1,2,4-triazinyl)>indoles.The combined yields of cycloadducts with tricarbalkoxytriazines exceeds 90 percent, with the production of γ-carbolines exceeding 80 percent.The regiochemistry of the adduct and the ratio of the products is determined mainly by electronic effects of the triazine substituents.Indole also ungergoes a cyclocondensation reaction with tetramethyl 1,2-diazine-3,4,5,6-tetracarboxylate to give trimethyl 5H-6-oxophenanthridine-2,3,4-tricarboxylate.