Rh-catalyzed [3 + 2] cyclization of (hetero)cyclic 1,3-dicarbonyls with 2-aminoarylboronic esters to access carbazolones

Abstract

We report herein the first Suzuki-type [3 + 2] cyclization of cyclic 1,3-dicarbonyls with readily available 2-aminoarylboronic esters to synthesize carbazolones. With environmentally benign EtOH/H₂O as solvent, a series of structurally and electronically diverse carbazolones can be readily obtained in a modular manner. This approach is mild, operationally simple, high yielding, scalable, and highly tolerant to moisture and air. Notably, it also exhibits excellent compatibility with various heterocyclic 1,3-dicarbonyls. The utility of this method has further been demonstrated by the late-stage functionalization of complex structures (e.g. styrylpyrone and simvastatin) and formal total synthesis of isocryptolepine.