Rhodium(III)‐Catalyzed C7‐Spiroannulation of Indolines with Maleimides: Facile Access to Aza‐Spiromulticycles

Abstract Herein, we report a chemo‐ and regioselective Rh‐catalyzed redox C7‐spiroannulation reaction of N ‐benzo[ d ]imidazole indolines with maleimides, resulting in a series of N ‐benzo[ d ]imidazole indoline fused azaspirocycles in up to 92% yield. The synthetic utility is demonstrated by the synthesis of highly functionalized nitrogen‐containing spiropolycyclic skeletons. The annulation reaction could also be performed with maleic esters and acrylates. The products were purified by simple filtration. The Rh catalyst can be recycled, and the reaction could be performed at gram‐scale using 0.5 mol% of catalyst, which makes this protocol potentially applicable in industry. Moreover, the efficient post‐modification of pharmaceutical molecules demonstrates its practicability.