The diastereoselective synthesis of pyrroloindolines by Pd-catalyzed dearomative cycloaddition of 1-tosyl-2-vinylaziridine to 3-nitroindoles

An efficient, diastereoselective synthesis of densely functionalized pyrroloindolines is reported. The reaction proceeds via cycloaddition of a vinylaziridine-derived Pd-stabilized 1,3-dipole to electron-deficient 3-nitroindoles. The reactions give the trans diastereoisomer with high selectivity; however, when a 4-substituent is present on the indole ring, a reversal of diastereoselectivity is observed.