This review with 272 references covers the literature published up to the end of February 2010 on the methods, other than the Mizoroki-Heck reaction, that have been developed in the last three decades to introduce carbon-carbon double bonds, frequently even in a stereocontrolled manner, onto heteroarene moieties by using transition-metal-catalyzed reactions that do not involve the use of stoichiometric amounts of organometallic reagents. The practicality and versatility of these methods with respect to substrate scope and operational costs are discussed. 1 Introduction 2 N-Alkenylation Reactions of Free (NH)-Azoles with Alkenyl­ Halides or Pseudohalides 3 Direct C-Alkenylation Reactions of Heteroarenes with Alkenyl­ Halides, Triflates, Phosphates, and 1,3-Dicarbonyl Compounds 4 Oxidative Coupling Reactions of Heteroarene C(sp^²)-H Bonds with Alkenes and Decarboxylative Alkenylation Reactions­ of Heteroarenecarboxylic Acids with Alkenes 5 Addition of Heteroarene C(sp^²)-H Bonds to Alkynes 6 Heteroarylcyanation of Alkynes 7 Conclusions

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