The transition-metal-catalyzed direct arylation of nonactivated aryl C−H bonds with iodoarenes has emerged as an important method for the construction of biaryls. Generally, the direct arylation reaction proceeds in the presence of stoichiometric Ag additives; moreover, the diarylation product is often unavoidable if there are two identical aromatic C−H bonds in the substrate. Herein we disclose an efficient Pd(OAc)2/trifluoroacetic acid/O2 catalytic system that promotes direct arylation reactions of a variety of aromatic C−H bonds with diverse iodoarenes under Ag-free conditions. The coupling reaction possesses a complete monoarylation selectivity. This approach provides a straightforward, facile, and economical route to biaryls. [ABSTRACT FROM AUTHOR]