Silver-free, palladium-catalyzed arylation of pyrrolo[1,2-a]quinoxaline C–H bonds with aryl bromides

Abstract

Arylation of C1–H bonds in pyrrolo[1,2-a]quinoxaline derivatives has hitherto been challenging. The sole method known until now suffers from a narrow scope of aryl iodides, while requiring an overstoichiometric amount of a silver additive and a high-molecular-weight phosphine ligand. Herein, we developed a method for coupling C1–H bonds in pyrrolo[1,2-a]quinoxalines with aryl bromides in the presence of simple reagents, namely Pd(OAc)₂ as catalyst, PPh₃ as ligand, K₂CO₃ as base, and 1,4-dioxane as solvent. This successful arylation did not require any silver additive and was tolerant of a wide range of functional groups such as aldehyde, nitro, cyano, ester, and heterocycles.