Stereoselective and Regiodivergent Allylic Suzuki–Miyaura Cross-Coupling of 2‑Ethoxydihydropyranyl Boronates: Synthesis and Confirmation of Absolute Stereochemistry of Diospongin B

Oxygen-containing heterocycles such as pyrans are a common substructure present in a variety of natural products and pharmaceutical drugs. Highly functionalized 4- and 6-aryl/heteroaryl dihydropyran derivatives are assembled by a highly stereoselective, ligand-controlled regiodivergent sp3–sp2 Suzuki–Miyaura cross-coupling of a 2-ethoxy dihydropyranyl boronate derived from a catalytic enantioselective inverse-electron-demand oxa­[4 + 2] cycloaddition. The scope and selectivity of this method were assessed along with an application to a concise total synthesis of the diarylheptanoid natural product diospongin B.