Diels-Alder reactions of the 1-methylpyrano [3, 4-b] indol-3-one 1a with less than two equivalents of methyl acrylate and methyl vinyl ketone occur with complete regioselectivity to yield the corresponding 3-substituted 1-methyl-1, 2-dihydrocarbazole derivatives 3. Cycloadditions of the N-acetyl-1-methylpyrano [3, 4-b] indol-3-one 1b with the same dienophiles proceed at a much slower rate to yield adducts incorporating two molecules of ...
