A Robust and Efficient Catalyst Possessing an Electron-Deficient Ligand for the Palladium-Catalyzed Direct Arylation of Heteroarenes

摘要

The exploration of the direct arylation capacity of a unique, thermally stable, and air-stable Pd-0-phosphine catalyst is reported. Besides decisively contributing to catalyst robustness, the electron-deficient trifluoromethyl-substituted triphenylphosphine ligands make the palladium center more electron-deficient and accelerate the direct arylation step. The combination of only 0.5-2 mol-% of the catalyst and a substoichiometric quantity of pivalic acid generates an efficient system to promote biaryl-forming reactions of a broad range of electronically varied hetarenes and aryl bromides. The observed regioselective arylations suggest that a concerted metalation-deprotonation pathway is involved in the C-H activation step.