Dehydrogenative Lactonization of Diols in Aqueous Media Catalyzed by a Water-Soluble Iridium Complex Bearing a Functional Bipyridine Ligand

A new catalytic system for the dehydrogenative lactonization of a variety of benzylic and aliphatic diols in aqueous media was developed. By using a water‐soluble, dicationic iridium catalyst bearing 6,6′‐dihydroxy‐2,2′‐bipyridine as a functional ligand, highly atom economical and environmentally benign synthesis of various lactones was achieved in good to excellent yields. Recovery and reuse of the catalyst were also accomplished by a simple phase separation and the recovered catalyst maintained its high activity at least until the fifth run. In the lactone zone: A new catalytic system for the dehydrogenative lactonization of diols in aqueous media is developed. By using a water‐soluble dicationic iridium catalyst bearing 6,6′‐dihydroxy‐2,2′‐bipyridine as a functional ligand, highly atom economical and environmentally benign synthesis of various lactones is achieved. The recovery and reuse of the catalyst by a simple procedure is also accomplished.