Enantioselective Copper-Catalyzed Intramolecular O−H Insertion: An Efficient Approach to Chiral 2-Carboxy Cyclic Ethers

A copper-catalyzed asymmetric intramolecular O-H insertion of ω-hydroxy-α-diazoesters has been accomplished by using chiral spiro bisoxazoline ligands. This highly enantioselective intramolecular O-H insertion reaction provides an efficient approach to a variety of synthetically important chiral 2-carboxy cyclic ethers with different ring sizes as well as substitution patterns.