Reactions of 1,3-dipolar aldazines and ketazines with the dipolarophile dimethyl acetylenedicarboxylate

The prepared aldazines (aldehyde azines) and ketazines (ketone azines) were allowed to react with 2 mol of the acetylene derivative. The first products formed were pentalene azine derivatives, which in some cases underwent skeletal rearrangment into acyclic tetraene azines. The latter underwent, in the case of some aldazine products, further skeletal rearrangment into N-allyl pyrazoles. The occurence of these rearrangments is dependant on the nature of the aldehydes or ketones used.