Cyclization of ortho-cyclopropylphenyl benzamides in gas and liquid phases

The electron ionization (EI) and collision-induced dissociation (CID) spect ra of substituted N-(ortho-cyclopropylphenyl)benzamides 1-7 and N-[ortho-(1 -methylcyclopropyl)phenyl]benzamides 8-12 Were recorded. In addition to rou tine bond cleavages, the molecular ions (M+) of 1-12 undergo cyclization in to the corresponding 3-aryl-1-alkyl-1-ethyl-1H-benzoxazines and isomeric 5- ethyl-2-oxodibenzoazepines. The presence of a methyl group in the cycloprop yl 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 a cid. Traces of 5-ethyl-2-oxodibenzoazepine were also detected in gas chroma tography-mass spectrometry (GC-MS) analysis of the reaction mixture althoug h the yield was too low to allow its isolation. (C) 2001 American Society f or Mass Spectrometry.