Recent Advances in Palladium-Catalyzed Oxidative Couplings in the Synthesis/Functionalization of Cyclic Scaffolds Using Molecular Oxygen as the Sole Oxidant

Abstract

AbstractOver the past years, Pd(II)-catalyzed oxidative couplings have enabled the construction of molecular scaffolds with high structural diversity via C–C, C–N and C–O bond-forming reactions. In contrast to the use of stoichiometric amounts of more common oxidants, such as metal salts (Cu and Ag) and benzoquinone derivatives, the use of molecular oxygen for the direct or indirect regeneration of Pd(II) species presents itself as a more viable alternative in terms of economy and sustainability. In this review, we describe recent advances on the development of Pd-catalyzed oxidative cyclizations/functionalizations, where molecular oxygen plays a pivotal role as the sole stoichiometric oxidant.1 Introduction2 Oxidative C–C and C–Nu Coupling2.1 Intramolecular Oxidative C–Nu Heterocyclization Reactions2.1.1 C–H Activation2.1.2 Wacker/Aza-Wacker-Type Cyclization2.1.3 Tandem Wacker/Aza-Wacker and Cyclization/Cross-Coupling Reactions2.2 Intermolecular Oxidative C–Nu Heterocoupling Reactions2.3 Intramolecular Oxidative (C–C) Carbocyclization Reactions2.4 Intermolecular Oxidative C–C Coupling Reactions2.4.1 Cyclization Reactions2.4.2 Cross-Coupling Reactions2.4.3 Homo-Coupling Reactions3 Aerobic Dehydrogenative Coupling/Functionalization4 Oxidative C–H Functionalization5 Summary