title: A divergent synthesis of functionalized unsaturated delta-lactones from alpha-alkenoyl-alpha-carboxyl ketene dithioacetals.
abstract: A divergent synthesis of functionalized unsaturated delta-lactones 2, 3, 4, and 5 has been developed starting from the readily available alpha-alkenoyl-alpha-carboxyl ketene dithioacetals 1 in high to excellent yields under mild reaction conditions. Thus, 6-substituted 3-(1,3-dithiolan/dithian-2-ylidene)-3H-pyran-2(6H)-ones 2, obtained from a consecutive reduction with NaBH4 and acidic workup of 1 via a novel vinylogous Pummerer cyclization, can be further transformed into alpha-pyranones 3, 4, and 5 upon a sequential isomerization catalyzed by triethylamine (to give 3), followed by dethioacetalization (to give 4) or a formylation with Vilsmeier reagent (to give 5).
authors.affiliation: Department of Chemistry, Northeast Normal University, Changchun, 130024, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Mang
authors.initials: M
authors.lastname: Wang
authors.forename: Bing
authors.initials: B
authors.lastname: Li
authors.forename: Qun
authors.initials: Q
authors.lastname: Liu
authors.forename: Yulong
authors.initials: Y
authors.lastname: Zhao