The Thorpe–Ingold effect is a key factor that affects the ring-closure rates and efficiency, as well as the structure of products in some ring-closure reactions. The reaction of vicinal amino primary alcohol hydrogen sulfates and carbon disulfide in the presence of potassium hydroxide produces the desired 4, 4-disubstituted thiazolidine-2-thiones, and their isomers 5, 5-disubstituted derivatives companying with their oxygen analogues 4, 4-disubstituted ...