Recent advances in Pd-catalyzed oxidative couplings in the synthesis/functionalization of cyclic scaffolds using molecular oxygen as the sole oxidant

Over the past years, Pd(II)-catalyzed oxidative couplings enabled the achievement of molecular scaffolds with high structural diversity via C−C, C-N and C-O bond-formation 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 in 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 Pd-catalyzed oxidative cyclizations/functionalizations, where molecular oxygen plays a pivotal role as the sole stoichiometric oxidant. 1 Introduction 2 Oxidative C-C and C-Nu Coupling 2.1 Intramolecular Oxidative C-Nu Heterocyclization Reactions 2.1.1 C-H Activation 2.1.2 Wacker/aza-Wacker Type Cyclization 2.1.3 Tandem Wacker/aza-Wacker and Cyclization/Cross Coupling Reactions 2.2 Intermolecular Oxidative C-Nu Heterocoupling Reactions 2.3 Intramolecular Oxidative (C-C) Carbocyclization Reactions 2.4 Intermolecular Oxidative C-C Coupling Reactions 2.4.1 Cyclization Reactions 2.4.2 Cross-Coupling Reactions 2.4.3 Homo-Coupling Reactions 3 Aerobic Dehydrogenative Coupling/Functionalization 4 Oxidative C-H Functionalization 5 Summary