Formation and thermal decomposition of adducts of phthalimidonitrene with spiro(1-pyrazolinecyclopropanes)

Abstract

Oxidation ofN-aminophthalimide with lead tetraacetate in the presence of spiro(1-pyrazolinecyclopropanes) at temperature from −20°C to −30°C resulted in the formal generation of phthalimidonitrene followed by its addition at the N=N bond of the pyrazoline ring to form 5(3)-substitutedN-{spiro[1-pyrazolinio-3(5),1′-cyclopropane]}-N-phthalimidoamides (azimines), whose regioisomeric compositions were determined to a large extent by the nature of the substituents in the pyrazoline ring. The structures of phthalimidoazimines were established based on the NMR spectra and X-ray diffraction data. Thermal conversions of the resulting adducts, which proceeded either with retention or with opening of the spiro-fused cyclopropane ring, were studied.