1,4-Dithiane-2,5-diol undergoes bifunctional squaramide catalyzed sulfa-Michael/aldol cascade reaction with chalcones to afford trisubstituted tetrahydrothiophenes. It participates in diastereoselective [3+3] cycloaddition with azomethine imines catalyzed by 1,4-diazabicyclo[2. 2. 2]octane. It is a mercaptoacetaldehyde dimer and an efficient synthon for incorporating a thiol group to in situ generated nitroalkenes.