Palladium-Catalyzed Direct Arylation of Polyfluoroarenes for Accessing Tetra-ortho-Substituted Biaryls: Buchwald-type Ligand Having Complementary −PPh2 Moiety Exhibits Better Efficiency

The first general examples of direct C–H arylation of electron-deficient polyfluoroarenes with challenging di-ortho-substituted aryl­(heteroaryl) chlorides for tetra-ortho-substituted biaryl synthesis are reported. Key to success is the use of Buchwald-type biaryl phosphine ligand, notably with inexpensive −PPh2 moiety (instead of −PCy2 group). Pd­(OAc)2 associated with ligand L9 exhibits even higher efficiency than the corresponding SPhos toward this reaction. A wide range of sterically hindered di-ortho-substituted chloroarenes bearing electron-donating or -withdrawing groups are found applicable. Excellent product yields are obtained under mild reaction conditions, and the catalyst loading down to 0.25 mol % of Pd can also be achieved.