Catalytic Asymmetric Synthesis of [2,3]-Fused Indoline Heterocycles through Inverse-Electron-Demand Aza-Diels-Alder Reaction of Indoles with Azoalkenes

An unprecedented catalytic asymmetric inverse-electron-demand aza-Diels–Alder reaction of indoles with in situ formed azoalkenes is reported. A diverse set of [2,3]-fused indoline heterocycles were achieved in generally good yields (up to 97 %) with high regioselectivity and diastereoselectivity (>20:1 d.r.), and with excellent enantioselectivity (up to 99 % ee).