[5C + 1S] Annulation:  A Facile and Efficient Synthetic Route toward Functionalized 2,3-Dihydrothiopyran-4-ones

A facile and efficient synthetic route toward highly substituted 2,3-dihydrothiopyran-4-ones 2 has been developed via a formal [5C + 1S] annulation of readily available α-alkenoyl ketene-(S,S)-acetals 1 with sodium sulfide nonahydrated salt (Na2S·9H2O) and utilized in the synthesis of 2-(4-chlorophenyl)-6-(morpholin-4-yl)-4H-thiopyran-4-one 5l, an inhibitor of DNA-dependent protein kinase (DNA-PK).