Oxygen as Oxidant in Palladium-Catalyzed Inter- and Intramolecular Coupling Reactions

Abstract

Facile palladium-catalyzed cyclizations of arylaminoquinones giving biologically important carbazoloquinones in high yields have been performed with oxygen as the single oxidant. By a slight modification of the catalyst, diphenylamine, diphenyl ether, and related compounds can be cyclized. The system could also be used in intermolecular couplings between naphthoquinones and benzene or naphthalene.

A General Method for Copper-Catalyzed Arene Cross-Dimerization

“…However, oxygen can sometimes be used as the stoichiometric oxidant avoiding generation of heavy metal waste. 10 …”

Acid‐Free Synthesis of Carbazoles and Carbazolequinones by Intramolecular Pd‐Catalyzed, Microwave‐Assisted Oxidative Biaryl Coupling Reactions – Efficient Syntheses of Murrayafoline A, 2‐Methoxy‐3‐methylcarbazole, and Glycozolidine

“…4‐Methoxy‐5 H ‐benzo[ b ]carbazole‐6,11‐dione (13b): 26b Orange solid, yield 252 mg (91 %), m.p. > 250 °C.…”

Heterocycle Synthesis Based on Palladium-Catalyzed C-H Bond Functionalization Methods

“…A key problem in developing catalytic transformations was the reoxidation of the catalyst. Only recently, such reactions were made catalytic by using appropriate cooxidants [52].…”