Synthesis of arylsulfonyl-substituted indolo[2,1-a]isoquinolin-6(5H)-one derivatives via a TBAI-catalyzed radical cascade cyclization

We have developed a metal-free radical cascade reaction of N -substituted 2-aryl indoles with readily available sulfonyl hydrazides for the rapid construction of arylsulfonyl-substituted indolo[2,1- a ]isoquinolin-6(5 H )-one derivatives. With the TBAI–TBHP catalytic system, a broad series of structurally diverse indolo[2,1- a ]isoquinolin-6(5 H )-one derivatives were obtained in moderate to excellent yields. The reaction features mild reaction conditions, operationally easiness, scaled-up feasibility, and high functional-group-tolerance. A metal-free radical cascade reaction of N -substituted 2-aryl indoles with readily available sulfonyl hydrazides for the rapid construction of structurally diverse indolo[2,1- a ]isoquinolin-6(5 H )-one derivatives has been developed.