1. Field of the Invention
The present invention relates to an improved process for the preparation of aryl ethers and, more especially, to the preparation of aliphatic/aromatic ethers by reacting an aliphatic halide with a phenolate or a naphtholate.
2. Description of the Prior Art
Processes of the aforenoted type are well known to the prior art. In particular, the synthesis of alkyl/aryl ethers via phase-transfer catalysis, i.e., by reacting an aqueous solution of a phenol with a solution of a haloalkane in a water-immiscible organic solvent, in the presence of a quaternary ammonium compound and an inorganic base, is known. Such process is described, for example, in Synthesis, pages 441-456 (1973), and in Agnew. Chem. Int. Ed. Engl., 13, pages 170-179 (1974).
The disadvantage of this type of process is that it requires large amounts of water. Indeed, it is even necessary to treat the waste waters before they are discarded. Furthermore, there are particular cases in which the presence of water is harmful; the water can at least partially degrade one of the reactants; it can also favor secondary reactions such as, for example, reactions involving C-alkylation of polyphenols by chloroalkenyl compounds.
And the French Pat. No. 2,255,279 describes the synthesis of alkyl/aryl ethers by reacting an aliphatic halide with a phenol, in the presence of an alkaline agent, in a polar solvent.
Although this latter process does not require the use of water, same is not suitable for application on an industrial scale because it involves expensive solvents which are difficult to handle.