STUDIES ON ENETHIOLS .V. SYNTHESES OF ALPHA-THIOACYLLACTONES AND ALPHA-THIOACYLTHIOLLACTONES . STRUCTURE DETERMINATION BY NMR SPECTROSCOPY

α-Thioacyllactones and α-thioacylthiollactones have been prepared in moderate to good yields by action of H2S and HCl on the α-acyl-analogues. NMR and IR studies show that the aliphatic thioacyl compounds exist as equilibrium mixtures of the cis- and the trans-enethiol forms, whereas the thioaroyllactones are present exclusively as intramolecularly H-bonded cis-enethiols. The NMR spectra are discussed and the influence of different solvents on chemical shifts and coupling constants are also described and discussed. The syntheses and properties of some methylated and acetylated α-thioacyllactones are presented, and their absolute configurations determined by NMR spectroscopy. © 1969.