Rhodium‐Catalyzed C−H Activation‐Based Construction of Axially and Centrally Chiral Indenes through Two Discrete Insertions

Reported herein is asymmetric [3+2] annulation of arylnitrones with different classes of alkynes catalyzed by chiral rhodium(III) complexes, with the nitrone acting as an electrophilic directing group. Three classes of chiral indenes/indenones have been effectively constructed, depending on the nature of the substrates. The coupling system features mild reaction conditions, excellent enantioselectivity, and high atom‐economy. In particular, the coupling of N‐benzylnitrones and different classes of sterically hindered alkynes afforded C−C or C−N atropochiral pentatomic biaryls with a C‐centered point‐chirality in excellent enantio‐ and diastereoselectivity (45 examples, average 95.6 % ee). These chiral center and axis are disposed in a distal fashion and they are constructed via two distinct migratory insertions that are stereo‐determining and are under catalyst control. Rhodium‐catalyzed C−H activation of nitrones and coupling with different classes of sterically hindered alkynes afforded C−C or C−N atropochiral and C‐centered point‐chiral indenes in excellent enantio‐ and diastereoselectivity. The chiral center and axis are disposed in a distal fashion, and they are constructed via two uncorrelated stereo‐determining steps.