Rhodium‐Catalyzed Cascade Reactions of Indoles with 4‐Hydroxy‐2‐Alkynoates for the Synthesis of Indole‐Fused Polyheterocycles

Abstract Herein, an efficient and regioselective Rh(III)‐catalyzed [4+2] annulation/lactonization cascade of indoles with 4‐hydroxy‐2‐alkynoates at room temperature to access the furo[3′,4′:4,5]pyrimido[1,6‐ a ]indole‐1,5(3 H ,4 H )‐diones is described. This method features mild reaction conditions, operational simplicity, excellent regioselectivity, broad substrate scope with good functional group tolerance, and good to excellent yields. magnified image