Rhodium-Catalyzed C–H Activation of Indoles for the Construction of Spiroindole Scaffolds

Abstract Spiroindoles are key scaffolds in a large number of natural products, pharmaceuticals, and agrochemicals. Selective C–H activation has emerged as a powerful synthetic approach to streamline the synthesis of substituted spiroindoles. To date, various 2- and 3-indolyl-tethered aza-spiro-centers have been successfully achieved via C–H activation. However, introduction of spiro-containing systems onto the benzenoid core of indole still remains challenging. Herein, a method of Rh(III)-catalyzed selective C7-H activation/cyclization of indole with maleimide to afford novel spiroindole derivatives is reported, which incorporate both succinimide and spirocycle into indole unit. Gram-scale synthesis demonstrates the utility of this protocol, further modification via click chemistry offered a novel scaffold as a versatile spiro linker.