ON THE REACTION OF 1-AZA-2-AZONIAALLENE SALTS WITH ISOCYANATES

1-Aza-2-azoniaallene salts 3, prepared in situ from geminal chloroalky lazo compounds 2 with Lewis acids, react with isocyanates 4 to give 4, 5-dihydro-5-oxo-3H-1,2,4-triazolium salts 6 and 4,5-dihydro-5-oxo-1H-1 ,2,4-triazolium salts 7, respectively. The intramolecular cyclization of 3u opens a new route to cinnolinium salts 11. Allenes 3 react with isobutene to give pyrazolium salts 8. According to AM1 calculations th e cycloadditions of 3 to isocyanates proceed in two steps via acylium salts 5 ds intermediates. Mechanistically, the rearrangements 6 --> 7 resemble Wagner-Meerwein rearrangements rather than pericyclic [1,5]-s igmatropic shifts.