A. Aranyos et al., Novel electron-rich bulky phosphine ligands facilitate the palladium-catalyzed preparation of diaryl ethers, J AM CHEM S, 121(18), 1999, pp. 4369-4378
A general method for the palladium-catalyzed formation of diaryl ethers is
described. Electron-rich, bulky aryldialkylphosphine ligands, in which the
two alkyl groups are either tert-butyl or 1-adamantyl, are the key to the s
uccess of the transformation. A wide range of electron-deficient, electroni
cally neutral and electron-rich aryl bromides, chlorides, and triflates can
be combined with a variety of phenols with the use of sodium hydride or po
tassium phosphate as base in toluene at 100 degrees C. The bulky yet basic
nature of the phosphine ligand is thought to be responsible for increasing
the rate of reductive elimination of the diaryl ether from palladium.