Diastereoselective Synthesis of Biheterocyclic Tetrahydrothiophene Derivatives via Base-Catalyzed Cascade Michael-Aldol [3 + 2] Annulation of 1,4-Dithiane-2,5-diol with Maleimides

A highly diastereoselective intermolecular [3 + 2] annulation of 1,4-dithiane-2,5-diol to maleimides has been developed by using DABCO as a catalyst, which provides a series of highly functionalized biheterocyclic tetrahydrothiophene derivatives containing tetrahydrothiophene and pyrolidine backbones in excellent yields and diastereoselectivities (up to 98% yield and >20:1 d.r.). The cascade Michael-aldol reaction is capable of tolerating organic solvents as well as water.