Iridium-catalyzed asymmetric cascade allylation/lactonization of methyl salicylates: enantioselective construction of chiral benzodioxepinones

An efficient asymmetric cascade allylation/lactonization of methyl salicylates has been achieved. The utilization of chiral-bridged biphenyl phosphoramidite ligand L3 resulted in good yields (up to 85%) and enantioselectivity (up to 95% ee) for the construction of a wide range of chiral benzodioxepinones with tolerance to diverse substituents. This reaction is featured by low catalyst loading, commercially available substrates and a broad substrate scope. Control experiments indicate that a relay catalytic pathway and kinetic resolution of racemic VEC might occur. In this transformation, the chiral-bridged phosphoramidite ligand L3 shows some advantages in enantioselective control compared to its BINOL-derived counterpart.