Brønsted acid catalyzed multicomponent synthesis of N-arylindole and N-arylbenzo[e]indole

Abstract

The most preferred heterocyclic indole core was de novo assembled by a multicomponent reaction (MCR) from inexpensive and broadly available anilines, 4-hydroxycyclohexanone or 2-tetralone, and 2,2-dimethoxyacetaldehyde via an acid catalyzed cascade aldol condensation-deprotonative aromatization-intramolecular cyclization process. As opposed to many other MCR approaches, this protocol delivered both C2 and C3-free indoles under environmentally benign conditions. The scope of the reactions was scouted and more than 40 derivatives were described