Asymmetric Synthesis of Trisubstituted Tetrahydrothiophenes via in Situ Generated Chiral Fluoride-Catalyzed Cascade Sulfa-Michael/Aldol Reaction of 1,4-Dithiane-2,5-diol and α,β-Unsaturated Ketones
A chiral fluoride-catalyzed asymmetriccascade sulfa-Michael/aldol condensation reaction of 1,4-dithiane-2,5-diol and a series of α,β-unsaturated ketones is described to access chiral trisubstituted tetrahydrothiophene derivatives. The target products, including the spiro tetrahydrothiophene derivatives bearing a five-, six-, and seven-membered ring, were highly functionalized and showed high ee value
A bifunctional squaramide catalyzed sulfa-Michael/aldol cascade reaction between 1,4-dithiane-2,5-diol and chalcones with a low catalyst loading has been developed. Trisubstituted tetrahydrothiophenes with three contiguous stereogenic centers are obtained in a highly stereocontrolled manner. Additionally, a remarkable temperature effect on reaction efficiency was observed and a synthetically potential gram-synthesis was also conducted.