Structure Determination of Diastereoisomeric Thia-Michael Bis-adducts of Methyl (5-Methylidene-4-oxocyclopent-2-en-1-yl)acetate with Ethanethiol

Three of the four possible diastereoisomeric thia-Michael addition products of the reaction of methyl (5-methylidene-4-oxo-cyclopent-2-en-1-yl)acetate with ethanethiol have been isolated and characterized. The major diastereoisomer is all- trans , while the overall fraction of the minor cis,trans and trans,cis isomers does not exceed 30%. The diastereoisomer structure has been determined on the basis of characteristic coupling constants of CH protons of the cyclopentane ring in the 1 H NMR spectra.