Heterocycle Formation via Palladium-Catalyzed C-H Functionalization

Heterocyclic compounds are ubiquitous in natural products, pharmaceuticals, and agrochemicals. Therefore, the design of novel protocols to construct heterocycles more efficiently is a major area of focus in organic chemistry. In the past several years, cyclization reactions based upon palladium-catalyzed C–H activation have received substantial attention due to their capacity for expediting heterocycle synthesis. This review discusses strategies for heterocycle synthesis via palladium-catalyzed C–H bond activation and highlights recent examples from the literature. 1 Introduction 2 Intramolecular Cyclization via C–C Bond Formation 2.1 Arene/Arene Coupling 2.1.1 C–H Arylation with Aryl Halides 2.1.2 C(sp 2 )–H/C(sp 2 )–H Coupling 2.2 Arene/Alkene Coupling or Arene/Alkyne Coupling 2.2.1 Arene/Alkene Coupling 2.2.2 Arene/Alkyne Coupling 2.3 Arene/Alkane Coupling 2.3.1 C(sp 2 )–H Alkylation with Alkyl Halides 2.3.2 C(sp 3 )–H Arylation with Aryl Halides 2.3.3 C(sp 2 )–H/C(sp 3 )–H Coupling 3 Intramolecular Cyclization via C–N Bond Formation 4 Intramolecular Cyclization via C–O or C–S Bond Formation 5 Incorporation with Carbon Monoxide 6 Incorporation with Isonitrile 7 Incorporation with Olefin 8 Conclusions