Fe(iii)-catalyzed [4+2] annulation of anthranils and maleimides for pyrrolo[3,4-b]quinolinedione synthesis: application to rosettacin

Abstract

An efficient and straightforward protocol for synthesizing pyrrolo[3,4-b]quinolinediones from readily available anthranils and maleimides has been developed via iron(III)-catalyzed [4+2]-annulation. This one-pot reaction forms epoxypyrrolo[3,4-b]quinolines, which rearrange into quinolinediones. The method shows broad functional group tolerance, providing products in good to excellent yields. This strategy's gram-scale synthesis and synthetic utility were demonstrated by successfully preparing biologically significant molecules, including Rosettacin, a known anti-topoisomerase alkaloid.