Alkyl aryl ethers are present in many naturally occurring and medicinally relevant compounds. Palladium- and copper-catalyzed C—O bond formation reactions have become effective strategies for their preparation. Recent developments in palladium- and copper-catalyzed arylations of aliphatic alcohols are summarized in this review. Palladium-catalyzed C—O cross coupling of various aliphatic alcohols with aryl halides could be efficiently realized in the presence of di-tert-buthyl biarylphosphine ligand, di-tert-buthylphosphino pentaphenylferrocene ligand, or di-adamantyl-substituted Bippyphos ligand developed by Buchwald, Hartwig, and Beller groups respectively. With the copper catalyst, 1, 10-phenanthroline and its derivatives, β-dicarbonyl compounds were served as the most efficient ligands. Generally, palladium-catalyzed C—O cross-coupling reactions display mild reaction conditions, good functional-group compatability, and broad substrate scope compared to the copper catalyst system. Moreover, the difference of the two catalytic systems including the choice of ligand, reactivity, β-H elimination and mechanism is discussed. The design and synthesis of new ligands are the key point for the further development of the C—O cross coupling.

Contents
1 Introduction
2 Pd-catalzyed arylation of alphatic alcohols
3 Cu-catalyzed arylation of alphatic alcohols
3.1 Cu-catalyzed C—O cross coupling reaction without ligand
3.2 Cu-catalyzed C—O cross coupling reaction in the presence of ligand
4 Comparative studies of two catalysts
4.1 Choice of ligands
4.2 Catalytic activity
4.3 β-H elimination reaction
4.4 Reaction mechanism
5 Conclusion and outlook