Synthesis of Tetrahydroindolizino[8,7-b]indole Derivatives in the Presence of Fe(OTf)3 or CF3SO3H through Intramolecular Dearomatization of Indole.

We have developed a convenient synthesis of tetrahydroindolizino[8,7-b]indole derivatives via intramolecular dearomatization of indole. Highly functionalized tetrahydroindolizinoindoles can be prepared in the presence of trifluoromethanesulfonic acid in good to excellent yields (up to >99% yield) with novel designed pyrrole-tethered indoles. The same products can also be synthesized through a mild Fe(OTf)3-catalyzed process in acceptable to good yields (up to 75% yield).