1,3-DIPOLAR CYCLOADDITION OF NITRILE OXIDES TO 8-AZAHEPTAFULVENES

Azaheptafulvenes (2) reacted readily with nitrile oxides (1) to give, as a rule, only adducts derived from a reaction involving the C=N moie ty of 2. The adducts consisted of a mixture of rapidly equilibrating ' 'spiro'' and ''condensed'' isomers, i.e. 6 reversible arrow 8, whose r atio was found to be dependent on substituents, temperature and solven t. The zwitterion (7) is an an appealing intermediate both for cycload dition and isomerisation. Decomposition of the adducts to benzene, R(1 )CN and R(2)NCO provided evidence in favor of the presence of the ''no rcaradiene'' derivatives (14) (undetectable by nmr) in equilibrium wit h 6 and 8. Only products arising from the ''spiro'' isomer (6) were ob tained in high yields in the catalytic hydrogenation of 6/8.