Synthesis and reactions of the first allenyl azo compounds

Several propargylhydrazines were prepared and then oxidized by manganese dioxide to generate short-lived 1,1-diazenes, which produced novel allenyl azo compounds (8) through [2,3] sigmatropic rearrangement. Isomerization of 8 or nucleophilic addition to the title compounds lead to hydrazones as well as pyrazole derivatives.