Rh(III)-Catalyzed C(sp 2 )–H Activation/Annulation for the Construction of Pyrrolo3,4- 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 pyrrolo3,4-bindolediones. 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.