Catalytic Asymmetric Dearomative Inverse-Electron-Demand Azo-Diels–Alder Reaction of Azoindoles with 2-Vinylindoles

Abstract Catalytic asymmetric inverse-electron-demand aza-Diels–Alder reactions are well-developed for the construction of aza-heterocyclic frameworks, while related azo-Diels–Alder reactions with azoarenes as dienes remain largely underexplored. Herein, we report a catalytic asymmetric dearomative IED azo-Diels–Alder cycloaddition of azoindoles with 2-vinylindoles. This protocol adopts a dual activation strategy that relies on C3-azo and N1-sulfonyl substituents to suppress the rearomatization of the indole core, facilitating efficient conversion under low-temperature conditions. A broad range of cis-pyridazino[4,3-b]indoles can be readily furnished through this approach in good to excellent yields with exceptional diastereo- and enantioselectivities (up to 94% yield, >99% ee, dr >20:1).