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

Herein, a Rh‐catalyzed redox C7‐spiroannulation reaction of N‐benzo[d]imidazole indolines with maleimides has been reported, chemo‐ and regio‐ selectively providing 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, which could be extended to maleic esters and acrylates. The products could be purified through simple filtration. The recyclable Rh catalyst and scale‐up synthesis with as low as 0.5 mol% catalyst loading makes this protocol potential application in industrial. Moreover, the efficient post‐modification of pharmaceutical molecules demonstrates its practicability.