Rh(III)-Catalyzed C(sp ² )–H Activation/Annulation for the Construction of Pyrrolo[3,4- b ]indolediones and Their Application as Fluorescent Chemosensors

This study presents an efficient strategy for synthesizing ring-fused indoles through Rh(III)-catalyzed C–H activation of N-arylpyrimidin-2-amines with maleimides, utilizing a pyrimidinyl directing group. The reaction proceeds via a formal [3 + 2] annulation, forming new C–C and C–N bonds and facilitating the streamlined construction of diversely functionalized pyrimidinyl-incorporated pyrrolo[3,4-b]indolediones. Furthermore, in the pursuit of potential metal-ion chemosensors, a new ring-fused indole-based fluorescent probe was identified, exhibiting high selectivity and sensitivity for Fe3+ detection.