Synthesis and Reactivity of 1-Allenyltriazenes.

1-Aryl-3,3-dialkyltriazenes have received considerable attention in the context of synthetic and medicinal chemistry. In contrast, the chemistry of other unsaturated triazenes is largely unexplored. The synthesis of 1-allenyltriazenes is described. This new class of compounds can be obtained by base-induced isomerization of 1-alkynyltriazenes. The latter are accessible by reaction of alkynyl Grignard reagents with lithium amides and nitrous oxide. 1-Allenyltriazenes were found to be thermally labile, but they can be stored without degradation at lower temperatures. In the presence of ZnCl2, 1-allenyltriazenes rearrange into N-aminopyrazoles.