Flash Vacuum Thermolysis of 2,3-Dihydro-1,4-oxathiin: Synthesis, Photoelectronic Spectroscopy, and Dienophilic Reactivity of Thioxoethanal

Article abstract of DOI:10.1021/jo00296a012

Thioxoethanal has been generated in the gas phase by vacuum thermolysis of 2,3-dihydro-1,4-oxathiin.Its characterization was performed by chemical trapping and photoelectron spectroscopy (PES).The PE HeI-HeII study led to the conclusion that thioxoethanal was obtained, with ethylene, as the only thermolysis product at 720 deg C.At higher temperatures, a cleavage into methanethial and carbon monoxide was observed.The results from the PE study, as well as MNDO calculations, indicate a very weak interaction between the formyl and thioformyl moieties of the molecule through the ? C-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.