Brønsted Acid Mediated Mono- and Di-substitution of Quinoxalines with Indoles: A Pathway to Indolocarbazole-Quinoxaline Scaffolds

Abstract

A versatile and efficient protocol for the mono- and di- substitution of quinoxalines with indoles has been developed, offering a direct pathway to indolocarbazole-quinoxaline scaffolds. By optimizing reaction conditions, selective coupling at the C-2 and C-3 positions of quinoxalines with diverse indole derivatives was achieved under transition metal-free conditions. Substrate scope evaluation revealed broad functional group tolerance and the synthetic utility was demonstrated at gram-scale synthesis and subsequent cyclization into novel indolocarbazole-quinoxalines. Mechanistic studies suggest an ionic pathway, highlighting the potential of this method for constructing biologically relevant heterocyclic architectures.