Azocarbenium ions 3, prepared in situ from 4-chromanone arylhydrazones 1, c
ycloadd readily to the triple bond of nitriles forming 3-spiro substituted
1,2,4-triazolium salts 4. The initial cycloadducts 4 cannot be isolated but
undergo consecutive reactions, e.g. [1,2]-shifts and ensuing ring enlargem
ent to provide 1, 2, 4-triazolo [3, 2-d] [1, 5] benzoxazepine compounds 5a-
5k, a kind of novel tricyclic heterocycles.