Mn-Mediated Cascade Cyclization of Isocyanides with Diaryphosphine Oxides: Access to Mono- and Bis-Heteroatom-Substituted Indolo[1,2- a ]quinoxalines

Herein, we report a novel manganese-mediated strategy for the cascade cyclization of indole isocyanides with diarylphosphine oxides and water, enabling the one-step formation of heteroatom-rich fused heterocycles via the simultaneous formation of C–C, C–O, and C–P bonds. This protocol features high regio- and chemoselectivities, mild conditions, operational simplicity, and broad functional group tolerance. Mechanistic investigations support the involvement of a radical pathway in this transformation. The synthetic utility of this method is demonstrated through the late-stage functionalization and preliminary biological evaluation of the newly formed products.