Base Mediated Tandem Vinylogous Addition and Cyclization of γ‑Phosphonyl/Sulfonyl Crotonates and Ynones: Synthesis of Functionalized 2‑Pyrones

A general method for highly functionalized 2-pyrones via a base-mediated sequential vinylogous addition and cyclization of γ-phosphonyl/sulfonyl crotonates and ynones are described. An exclusive E-geometry with respect to the newly generated olefin substituent at C3 of pyrone was observed. Imino glyoxalates and glycine imines similarly reacted with ynones to deliver 3-imino pyrones.