Flash vacuum thermolysis of 2,3-dihydro-1,4-oxathiin: Synthesis, photoelectronic spectroscopy, and dienophilic reactivity of thioxoethanal
Résumé
Thioxoethanal has been generated in the gas phase by flash vacuum thermolysis of 2,3-dihydro-1,4-osathiin. its characterization was performed by chemical trapping and photoelectron spectroscopy (PES). The PE HeI-HeII study led to the conclusion that thiooxethanal was obtained, with ethylene, as the only thermolysis product at 720°C. At higher temperatures, a cleavage into methanethial and carbon monoxide was observed. The results from this PE study, as well as MNDO calculations, indicate a very weak interaction between the formyl and thioformyl moieties of the molecule through the σC-C bond. The HOMO sulfur lone pair is only slightly stabilized by the inductive effect of the carbonyl group. These conclusions account for the observed dienophilic reactivity of thioxoethanal. © 1990 American Chemical Society.