Different reactivities of regioisomeric azimines, adducts of phthalimidonitrene with 5-bromospiro[1-pyrazoline-3,1′-cyclopropane]

The addition of the phthalimidonitrene fragment. resulting from oxidation of N-aminophthalimide by lead tetraacetate at -20 to -30 degreesC, to the N=N-bond of 5-bromospiro[1-pyrazoline-3,1'-cyclopropane] (1) affords, apart from the stable 5-bromoN-(spiro[1-pyrazolinio-3,1-cyclopropane])-N-phthalimidoamide (azimine 2), regioisomeric azimine 3, which is completely transformed into 3-acetoxy-N-(spiro[1-pyrazolinio-5,1'-cyclopropane])- N-phthalimidoamide (4) under the reaction conditions. The acetoxy group in this product easily. undergoes nucleophilic substitution on treatment with MeOH. NaN3. or the starting bromopyrazoline 1. The structures of azimines obtained were established using N M R spectra. and the structure of the product of reaction of 4 with 1 was additionally proved by X-ray difraction data.