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The significant number of papers and reviews published in this last decade testifies to the utility of the transition-metal-catalyzed direct C-H (hetero)arylation reactions of (hetero)arenes as efficient and powerful tools for the step- and atom-economical, regio- and chemoselective synthesis of natural and unnatural compounds. However, no review has so far been devoted to summarizing the application of these reactions in the synthesis of biologically active compounds. This review with 341 references aims to fill this gap, providing a comprehensive picture of the transition-metal-catalyzed intra- and intermolecular direct C-H (hetero)arylation reactions of (hetero)arenes with (hetero)aryl halides or pseudohalides that have been used as key steps of syntheses of unnatural biologically relevant compounds including pharmaceutical targets, up to the end of September 2015. Attention has also been directed to provide a brief description of the biological properties of the synthesized compounds. 1 Introduction 2 Syntheses via Intramolecular Direct (Hetero)arylation of (Hetero) arene Derivatives 3 Syntheses via Intermolecular Direct (Hetero)arylation Reactions 3.1 Of Arenes 3.2 Of Five-Membered Heteroarenes with One Heteroatom 3.3 Of Five-Membered Heteroarenes with Two Heteroatoms 3.4 Of Five-Membered Heteroarenes with Three and Four Heteroatoms 3.5 Of Five-Membered Heteroarenes Fused to a Six-Membered Heteroarene 3.6 Of Five-Membered Heteroarene Moieties of Tricyclic Heteroarenes 3.7 Of Six-Membered Heteroarenes 4 Syntheses of Nitrogen-Containing Polycyclic Heteroarene via One-Pot Palladium-Catalyzed Domino Direct Arylation/N-Arylation Reactions 5 Conclusions [ABSTRACT FROM AUTHOR]

In recent years, environmental and economic reasons have motivated the development of transition metal-free carbon-carbon bond forming reactions and some excellent reviews have covered this research area of particular interest for the pharmaceutical industry. However, none of these reviews has been specifically dedicated to summarize and discuss the results achieved in the rapidly growing field of the transition metal-free direct (hetero)arylation reactions of heteroarenes. This review, which covers the literature from 2008 to 2014, aims to provide a thorough insight into the synthetic and mechanistic aspects of these atom economic and environmentally benign reactions also highlighting their advantages and possible disadvantages compared to conventional methods for the synthesis of arylheteroarenes and biheteroaryls via transition metal-catalyzed reactions. [ABSTRACT FROM AUTHOR]

This review with 387 references covers the literature until the end of November 2013 on the synthesis of multiply arylated heteroarenes via highly selective palladium-catalyzed direct C-H arylation reactions of heteroarene derivatives with aryl halides or pseudohalides or aryliodonium salts. Particular attention has been made to describe the synthesis of biologically active compounds and substances that are privileged structural motifs in organic materials. The practicality, versatility, and limitations of the various developed arylation protocols are discussed. 1 Introduction 2 Synthesis of Multiply Arylated Five-Membered Hetero­arenes with One Heteroatom 2.1 Multiply Arylated Furan and Benzo[b]furan Derivatives 2.2 Multiply Arylated Thiophenes and Benzo[b]thiophene Derivatives 2.3 Multiply Arylated Pyrrole and Indole Derivatives 3 Synthesis of Multiply Arylated Five-Membered Hetero­arenes with Two or More Heteroatoms 3.1 Multiply Arylated Pyrazole and 2H-Indazole Derivatives 3.2 Multiply Arylated Isoxazole Derivatives 3.3 Multiply Arylated Oxazole Derivatives 3.4 Multiply Arylated Thiazole and Thiazole N-Oxide Derivatives 3.5 Multiply Arylated Imidazole and Imidazole N-Oxide Derivatives­ 3.6 Multiply Arylated 1,2,3-Triazole and 1,2,3-Triazole N-Oxide Derivatives 3.7 Diarylated 1,2,4-Triazole and 1,3,4-Thiadiazole Derivatives 3.8 Diarylated Sydnone, 2,1,3-Benzothiadiazole, and Tetrazole Derivatives 4 Synthesis of Multiply Arylated Six-Membered Hetero­arenes 4.1 Diarylated Pyridines, Pyridine N-Oxides, and Pyrazine N-Oxides 5 Synthesis of Multiply Arylated Compounds Formed by Five-Membered Heteroarenes Fused to Five-Membered Heteroarenes 5.1 Diarylated Thieno[2,3-b]thiophenes, Imidazo[1,2-b]pyrazoles, and Thiazolo[3,2-b]-1,2,4-triazoles 6 Synthesis of Multiply Arylated Compounds Formed by Six-Membered Heteroarenes Fused to Five-Membered Hetero­arenes 6.1 Diarylated Indolizines, Pyrimido[5,4-b]indolizines, Pyrrolo[2,3-b]pyridines, Pyrazolo[1,5-a]pyrimidines, Imidazo[1,2-a]pyridines, Imidazo[1,5-a]pyridines, Xanthines, Imidazo[1,2-b]tetrazines, Imidazo[1,2-a]pyrazines, and ­Furo[3,2-b]pyridines 7 Conclusions [ABSTRACT FROM AUTHOR]

In recent years, transition metal-catalyzed direct (hetero)arylation reactions of heteroarenes with (hetero)aryl halides and pseudohalides have received significant attention as eco-friendly and economic alternatives to classical methods for the construction of heteroaryl-(hetero)aryl CC bonds by transition metal-catalyzed cross-couplings involving the use of stoichiometric amounts of organometallic reagents. This critical review with 430 references covers the results obtained in the period January 2009 to February 2013 in the area of the transition metal-catalyzed direct inter- and intramolecular (hetero)arylation reactions of heteroarenes containing one heteroatom. Particular attention has been given to illustrate chemo- and site selectivity aspects of these reactions as well applications of these CC bond forming reactions in the synthesis of pharmaceutically relevant compounds, natural products and their analogues and precursors. The most recent advancements into the mechanism(s) of these reactions have also been briefly reported. [ABSTRACT FROM AUTHOR]

Review: [175 refs. [ABSTRACT FROM AUTHOR]