Synthesis of γ‑Thiapyrones by Diels–Alder/Retro-Diels–Alder Reaction of α‑Pyrones with 5‑H‑1,2,3-Thiadiazoles

The efficient synthesis of γ-thiapyrones by a base-mediated Diels–Alder/retro-Diels–Alder reaction of α-pyrones with 5-H-1,2,3-thiadiazoles is reported herein. Thioketenes in situ generated from thiadiazoles as electron-poor dienophile and electron-rich 4-hydroxy-2-pyrones as dienes are conjunctively transformed into a series of γ-thiapyrones with broad functional group compatibility in good to excellent yields (35 examples, 67% average yield).