A review on the advancement of ether synthesis from organic solvent to water

Abstract

Ethers have been synthesized by the different protocols such as Williamson ether synthesis, the Mitsunobu reaction, bimolecular dehydration, the Ullmann method, a transition metal-free coupling reaction between aliphatic alcohols and unsymmetric diaryliodonium salts, room temperature ionic liquid promoted synthesis, Cu(II) catalyzed synthesis, microwave assisted synthesis, and synthesis under solvent free micellar conditions. A good number of homogeneous Bronsted acids and Lewis acid based transition metals have also been reported as catalysts in the etherification of alcohols. The above mentioned pathway has exhibited some drawbacks including their deactivation through decomposition caused by the water formed during the course of the reaction. In many cases these methods also reveal the accumulation of a significant amount of acid at the end of the reaction due to the hydrolysis of Lewis acid catalysts such as metal oxides, which upon neutralization give a considerable amount of salts. A literature survey shows some reports on the use of phase transfer and polymer and clay supported catalysts for the synthesis of symmetrical and unsymmetrical ethers. To a synthetic chemist, an aqueous micellar solution is a good choice as a reaction medium for synthesizing several organic compounds. Micellar conditions are a new direction of study for ether synthesis as they are simple, efficient, economical and environmentally friendly.