PROTOTROPY IN THE SYSTEM -CLCH-N=N- - CYCLOADDITIONS OF 1-AZA-2-AZONIAALLENE CATIONS DERIVED FROM ALDEHYDES

1,3-Disubstituted 1-aza-2-azoniaallene salts 10 were obtained as react ive intermediates on oxidation of aldehyde hydrazones 7 with tert-buty l hypochlorite and treatment of the resulting (1-chloroalkyl)azo compo unds 8 with a Lewis acid (SbCl5). The allenes 10 underwent cycloadditi ons to the multiple bonds of nitriles, acetylenes, and olefins affordi ng the heterocyclic salts 12, which gave the free bases 12' with aqueo us NaOH. The critical point of this sequence lies in the prototropic r earrangement of 8 into the hydrazonyl chlorides 9, from which no heter ocumulenes 10 could be obtained. However, further chlorination of 7c l ed to the (1,1-dichloropropyl)azo compound 13, which gave the chloro s ubstituted allenium salt 14 on treatment with SbCl5. Cycloaddition of 14 to acetonitrile afforded the chloro substituted 1,2,4-triazolium sa lt 16. Conditions for slow rearrangements 8 --> 9 were found for compo unds 8 derived from primary or secondary alkanecarbaldehydes. However, for (1-chloroalkyl)azo compounds derived from benzaldehyde or pivalde hyde the prototropy 8 --> 9 was too fast to permit preparation of hete rocumulenes 10.