The use of 1,2-shifts in carbenes and nitrenes in the generation of novel heterocumulenes

Ethenedithione, S=C=C=S, has been generated in flash vacuum pyrolysis (FVP) reactions from isoxazolone and Meldrum's acid derivatives and characterized by IR, UV and mass spectrometry. Evidence for the existence of HN=C=C=S and its isomerization to thioformyl cyanide is also presented. The preparation and characterization of iminopropadienone derivatives RN=C=C=C=X (X = 0, S, or NR') from a variety of isoxazole compounds is described. These highly reactive cumulenes are formed via vinylidene, vinylnitrene, and ketenimine intermediates.