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Paper | Special issue | Vol 40, No. 2, 1995, pp.619-638
Published online, 1st January, 1970
DOI: 10.3987/COM-94-S50
1,3-Dipolar Cycloaddition of Nitrile Oxides to 8-Azaheptafulvenes

Remo Gandolfi, Anna Gamba, and Paolo Grünanger

*Dipartiment di Chimica Organica, Università di Pavia, V.le Taramelli 10, 27100 Pavia, Italy

Abstract

Azaheptafulvenes (2) reacted readily with nitrile oxides (1) to give, as a rule, only adducts derived from a reaction involving the C=N moiety of 2. The adducts consisted of a mixture of rapidly equilibrating “spiro” and “condensed” isomers, i.e. 68, whose ratio was found to be dependent on substituents, temperature and solvent. The zwitterion (7) is an appealing intermediate both for cycloaddition and isomerisation. Decomposition of the adducts to benzene, R1CN and R2NCO provided evidence in favor of the presence of the “norcaradiene” derivatives (14) (undetectable by nmr) in equilibrium with 6 and 8. Only products arising from the “spiro” isomer (6) were obtained in high yields in the catalytic hydrogenation of 6/8.