Fe-Catalyzed Pictet-Spengler-Type Cyclization via Selective Four-Electron Reductive Functionalization of CO_(2)

Main observation and conclusion Herein,we describe a novel catalytic Pictet-Spengler-type cyclization using CO_(2) as a nontoxic and sustainable C1 feedstock with envi-ronmentally benign and non-precious-metal iron as catalyst.The reaction is achieved by selective four-electron reduction of CO_(2) into methylene level intermediate through carefully tuning the reaction parameters.A variety of tetrahydro-B-carbolines and other nitro-gen-containing heterocycles can be easily obtained under mild conditions.Mechanistic studies have shown that tetrahy-dro-B-carbolines are probably obtained via spiroindolenine intermediates.