Organocatalytic Redox Deracemization of Cyclic Benzylic Ethers Enabled by An Acetal Pool Strategy

The first redox deracemization of a series of cyclic benzylic ethers, including 6H-benzo[c]chromenes, isochromans, and 1H-isochromenes, is described. An "acetal pool" strategy was adopted to harmonize the complete oxidation of secondary ethers with imidodiphosphoric acid catalyzed asymmetric transfer hydrogenation. The synthetic utility of the process was demonstrated by the effective deracemization of biologically active molecules of interest that are difficult to prepare by other methods.