Efficient Synthesis of Substituted Tetrahydrothiopyrano[2,3-<i>b</i>]thiopyran-4,5-diones by a Double Annulation Strategy from Dialkenoylketene Dithioacetals

Abstract

An efficient synthetic procedure for substituted 2,3,6,7-tetrahydrothiopyrano[2,3-b]thiopyran-4,5-diones by a double annulation strategy is described. The ring systems are made in good yields from readily available dialkenoylketene dithioacetals in the presence of either sodium sulfide nonahydrate/N,N-dimethylform­amide (DMF) or a sodium hydride/DMF/amine system.