Gas–liquid phase-transfer synthesis of phenyl ethers and sulphides with carbonate as base and Carbowax as catalyst

Abstract

When a mixture of a phenol (or thiol) and an alkyl halide is passed, in the gaseous state, through a solid bed of potassium carbonate (or sodium hydrogencarbonate) and catalytic amounts of Carbowax 6000, contained in a glass column at 170 °C, the corresponding ethers (or sulphides) may be collected at the outlet. The Carbowax acts in a similar manner to the crown ethers used in solid–liquid phase-transfer catalysis. The potassium carbonate–Carbowax combination allows the generation of anions up to a pK_a of ca. 12. The catalysis mechanism is discussed and the synthesis of several ethers and thioethers is reported, some of which are obtained only with difficulty by normal liquid–liquid phase-transfer catalysis.