Advances in Asymmetric Hydrogenation of Unfunctionalized Enol Ethers

Abstract

Asymmetric hydrogenation of enol ethers has emerged as a valuable and environmentally friendly method for the preparation of optically active cyclic and acyclic ethers, some of which have demonstrated substantial potential for application in the synthesis of valuable compounds and total synthesis of natural products. Over the past few decades, significant attention has been devoted to the use of transition-metal catalysts, particularly those containing chiral phosphine-phosphine, phosphine-amine, or carbene ligands, in the hydrogenation of unfunctionalized enol ethers. In parallel, frustrated Lewis pair catalysts have also been successfully applied in this transformation, enabling the efficient production of various chiral ethers. This review highlights the momentum and most notable advances in enantioselective hydrogenation of unfunctionalized enol ethers (with only alkyl and aryl substituents on the vinyl group). Owing to ubiquitous industrial interest, the utility in the synthesis of chiral ethers and related derivatives is included.