PREPARATION DE THIOCETONES ACYCLIQUES α-INSATUREES. DIMERISATION REGIOSELECTIVE EN 4H-DITHIINE-1,3

Article abstract of DOI:10.1016/S0040-4020(01)98882-9

α-Unsaturated acyclic thioketones 6 a-d were prepared by a retro-Diels-Alder reaction using flash thermolysis technique.They were detected at low temperature (blue coloured pyrolysate) but dimerize in solution as soon as the temperature rose to -60^o (case 6 a-c) and -20^o (case 6 d).The structure of 6 d was established by UV and NMR spectra taken at -60^o.Dimeric products were proved to be 4H-1,3 dithiin by spectral data and by univocal synthesis of 7 c and 7 d from the corresponding monomeric ketone. 1-3 Dithiin 7 d was isomerized at 190^o into the thermodynamic isomer (8).This observed orientation of dimerisation agrees with theorical results obtained from molecular frontier orbital calculations.