A New Biarylphosphine Ligand for the Pd-Catalyzed Synthesis of Diaryl Ethers under Mild Conditions

Reaction Scheme


An efficient, general palladium catalyst for C-O bond-forming reactions of secondary and primary alcohols with a range of aryl halides has been developed using the ligand�1. Heteroaryl halides, and for the first time, electron-rich aryl halides can be coupled with secondary alcohols. A diverse set of substrate combinations are possible with just a single ligand, thus obviating the need to survey multiple ligands.



Cs2CO3 (489 mg, 1.5 mmol, 1.5 equiv.) was added to an ovendried resealable screw-cap test tube and dried with flame under vacuum. To the tube were added (allylPdCl)2 (1 � 2.5 mol%) and RockPhos (2.4 � 6 mol%) under argon. The tube was evacuated and backfilled with argon (this process was repeated a total of 3 times). Toluene and the alcohol were added through the septum via syringe and the mixture was stirred at 90 �C in a pre-heated oil bath for 3 min. Aryl halide was added and the mixture was stirred vigorously for the indicated time. After the reaction was allowed to cool to room temperature, it was filtered through a layer of Celite eluting with EtOAc. The filtrate was concentrated in vacuo and the crude product was purified by flash chromatography



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