NEW ROUTES TO THIOKETENES AND PROPADIENETHIONE BY FLASH VACUUM THERMOLYSIS

The retro-Diels-Alder reaction under flash vacuum thermolysis (FVT) conditions was applied to the synthesis of simple unstabilized thioketenes. Alternatively, these reactive thiocarbonyl compounds were obtained by FVT elimination of methyltrimethylsilyl sulfide from silylated ketene dithioacetals (and for thioketene itself from methyl trimethylsilyl dithioacetate). A synthesis of propadienethione associating these two thermolytic processes is also reported. The thermolysis products were identified by low temperature IR spectroscopy and immediate quenching with gaseous dimethylamine leading to the corresponding thioamides. In the case of propadienethione, further reaction with the methanethiol formed in situ was observed. © 1990.