Iron-catalyzed cross etherification of alcohols to form unsymmetrical benzyl ethers

Abstract A Fe(II)-catalyzed direct synthesis of unsymmetrical benzyl ethers from two different alcohols has been developed. In the presence of a catalyst in situ generated by combining Fe(OTf) 2 (OTf = trifluomethanesulfonate) with a pyridine bis-imidazoline ligand, benzyl alcohols underwent cross dehydrative etherification with a wide range of aliphatic alcohols in good to excellent yields under mild, operationally simple conditions with low catalyst loading. The catalyst tolerates a number of functional groups in both coupling partners, and is highly chemoselective, affording no symmetrical ether by-products. Ligand is shown to play a crucial role to the success of this dehydrative transformation, and preliminary mechanistic studies indicate that a benzylic cation is involved in the cross etherification.