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 insitu 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).