Dearomative ipso-Cyclization to Spiropseudoindoxyls: An Extendable Approach To Access Indolo[3,2- c]quinolinones and Isocryptolepine

Org Lett. 2024 Jan 12;26(1):68-72. doi: 10.1021/acs.orglett.3c03643. Epub 2023 Dec 31.

Abstract

A metal-free oxidative intramolecular dearomative spirocyclization of indole-3-formyl-2-carboxamides has been developed for the first time, affording spiropseudoindoxyls in good yields. This domino process proceeds through sequential oxidation, decarboxylation and ipso-arylation. The unique feature of this approach includes the compatibility of N-protected-indole-2-carboxamides. Further, a hitherto unknown rearrangement of spiropseudoindoxyls to indoloquinolones has been achieved. The synthetic utility of this strategy has also been showcased by the construction of a natural alkaloid, isocryptolepine.