Recent Developments in Pd-Catalyzed Direct Arylations of Heteroarenes with Aryl Halides

The direct arylation of heteroaromatic compounds with aryl halides using palladium catalysts has significantly been developed as an effective method for making (hetero)aryl-heteroaryl bonds, which are frequently found in biologically active compounds and functional materials. However, issues regarding costly reagents, regioselectivity, and harsh reaction conditions have to be solved to really compete with the classical transition metal-mediated cross-coupling procedures involving stoichiometric organometallic reagents. In this review, the most relevant developments aimed at solving these issues are summarized.