Asymmetric Oxidative Lactonization of Enynyl Boronates

Abstract Oxidation of C−B bonds is extensively used in organic synthesis, materials science, and chemically biology. However, these oxidations are usually limited to the oxidation of C(sp 3 )−B and C(sp 2 )−B bonds. The C(sp)−B bond oxidation is rarely developed. Herein we present a novel strategy for the preparation of γ ‐lactones via the oxidation of enynyl boronates. This process successively involves the C(sp)−B bond oxidation, the epoxidation of C−C double bond and the lactonization. This protocol provided various γ ‐lactones and unsaturated butenolides efficiently that are prevalent in numerous nature products and bioactive molecules. Most importantly, asymmetric oxidative lactonization of enynyl boronates was also achieved, providing chiral γ ‐lactones in high enantioselectivities and diastereoselectivities. The versatile transformations and ubiquity of γ ‐lactones shed light on the importance of this strategy in the construction and late‐stage functionalization of complex molecules.