1-aza-2-azoniaallene salts: reactions with azomethines and other N-nucleophiles

Azomethines undergo nucleophilic addition to 1-aza-2-azoniaallene salts 7 t o furnish N-(azoalkyl)iminium salts (e.g. 10, 12, 13). With cyclic hydrazon es such as pyrazole or indazole, heterocumulenes 7 afford bicyclic 1,2,4,5- tetrazinium salts (e.g. 14, 16), or simple N-adducts such as 15, 17. On the other hand, with open-chain hydrazones azinium salts 19 are formed. Benzot riazole and the aziridine 21 react with 1-aza-2-azoniaallene salts 7 to aff ord (azoalkyl)ammonium salts 20, 22. The heterocumulenes 7 undergo cycloadd ition across the C=N double bond of the azirine 23 to furnish azirenotriazo lium salts 25, while with the 1-aza-2-azoniaallene salt 3a the triazolium s alt 28 was formed. The constitutions of compounds 22, 25a and 28 were confi rmed by X-ray structural analyses.