FeCl₃/KI-Catalyzed Tandem Oxidative Cyclization for Switchable Total Synthesis of Luotonin A, B and Derivatives

A total synthesis strategy was developed for the synthesis of luotonin A, B and their analogues using synergistic FeCl3/KI-catalyzed oxidative cyclization. This protocol utilizes cheap and widely available N-propargyl 2-methyl-quinazolinones and arylamines under mild conditions, and it has a wide substrate scope and high atom economy. Different natural products (luotonin A, B and derivatives) can be synthesized via a unique switchable approach. Further transformations from luotonin B to luotonin E and structural modification of natural products demonstrate the potential applications of this method. Moreover, camptothecin can also be modified with the reported protocol to afford the hydroxyl-substituted product.