Synthesis of Polycyclic Heteroarenes via Rh(III)-Catalyzed Twofold C-H Activation of 3-Aryl-2<i>H</i>-benzo[<i>b</i>][1,4]oxazines and Annulation with α-Diazo-β-ketoesters

An efficient Rh(III)-catalyzed annulation between 3-aryl-2<i>H</i>-benzo[<i>b</i>][1,4]oxazines and α-diazo-β-ketoesters was developed, affording a series of polycyclic heteroarenes in moderate to excellent yields with good functional group compatibility. The procedure featured high efficiency, redox neutrality, twofold <i>ortho</i>-C-H activation, and dual [4 + 2] annulation. Moreover, several important intermediates and products have been isolated as powerful evidence for the proposed reaction mechanism.