Cross-Coupling Reactions of Polyhalogenated Heterocycles

Abstract Palladium-catalyzed cross-coupling reactions of polyhalogenated heterocycles provide a convenient access to multifold arylated and alkynylated ring systems with a broad spectrum of physical and medicinal properties. Products include thiophenes, selenophenes, pyrroles, indoles, furans, benzofurans, pyrazoles, pyridines, quinolines, pyrimidines, pyrazines, naphthyridines, quinoxalines, and others. The regioselectivity of the coupling reactions is controlled by a combination of electronic and steric parameters. While a number of couplings can be carried out essentially under standard conditions, others require the use of more sophisticated ligands and a thorough optimization of the conditions, such as solvent, temperature, or reaction time. The present Account provides a personalized overview of coupling reactions of polyhalogenated heterocycles. 1 Introduction 2 Thiophenes 3 Selenophenes 4 Pyrroles and Indoles 5 Furans and Benzofurans 6 Pyrazoles 7 Pyridines 8 Quinolines 9 Pyrimidines and Pyrazines 10 Naphthyridines and Quinoxalines 11 Miscellaneous 12 Conclusions