PIFA-mediated intramolecular N-arylation of 2-aminoquinoxalines to afford indolo[2,3-b]quinoxaline derivatives†

Abstract

We present the PIFA-mediated intramolecular N-arylation of 2-aminoquinoxalines at room temperature for the first time. This method provides a wide range of indolo[2,3-b]quinoxalines in good to excellent yields within a short time. The C–H bond functionalization occurs without the need for an inert atmosphere or additives. Additionally, a double C–H bond functionalization was observed, where the first reaction forms a C–N bond (N-arylation) and the second forms a C–O bond, yielding an acetal-functionalized product. Mechanistic investigations suggest that the C–H bond functionalization proceeds through an ionic mechanism, whereas acetal functionalization follows a radical pathway. This method extends to the derivation of indoloquinoxalines, including the target compound BIQMCz.