The electron ionization (EI) and collision-induced dissociation (CID) spectra of substituted N-(ortho-cyclopropylphenyl)benzamides 1-7 and N-[ortho-(1-methylcyclopropyl)phenyl]benzamides 8-12 were recorded. In addition to routine bond cleavages, the molecular ions (M+) of 1-12 undergo cyclization into the corresponding 3-aryl-1-alkyl-1-ethyl-1H-benzoxazines and isomeric 5-ethyl-2-oxodibenzoazepines. The presence of a methyl group in the cyclopropyl ring (compounds 8-12) makes the formation of 5-ethyl-2-oxodibenzoazepine less favorable. In accord with mass spectrometric predictions, compound 13 (3-p-tolyl-1-ethyl-1H-benzoxazine) was obtained as a major product of the reaction of N-(ortho-cyclopropylphenyl)-4-methylbenzamide 1 with sulfuric acid. Traces of 5-ethyl-2-oxodibenzoazepine were also detected in gas chromatography-mass spectrometry (GC-MS) analysis of the reaction mixture although the yield was too low to allow its isolation.

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The isomerization of M + ' of o-carboxy-and o-carboxamidocyclopropylbenzenes into five-and six-membered heterocycles due to the ortho effect has been demonstrated by means of electron impact mass spectra, high-resolution mass spectrometry data and metastable ion spectra. The criteria for the quantitative estimation of the degree of cyclopropane cyclization into these isomeric cycles were formulated. The nature and quantity of heterocyclic ions proved to be in good accord with the results for cyclization of the same cyclopropanes in the strong acid solutions.

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