Electron impact and chemical ionization mass spectra of aryl ureas

Abstract

The electron impact and chemical ionization mass spectra of a series of N,N,'-diaryl ureas have been compared. The electron impact mass spectra indicate rearrangements leading to two pairs of aromatic amines and isocyanates, either as ions or molecdes. The chemical ionization mass spectra showed the formation of protonated amines and isocyanates via rearrangement.

Cyclization of the substituted N-(Ortho-cyclopropylphenyl)-N′-aryl ureas and thioureas in the gas phase and solution

“…The cyclization products of the molecular ions for these benzamides were identical to those synthesized in the condensed phase [4,5]. In the present study, we continue research in this area, investigating the possibility of rearrangements of substituted N-(ortho-cyclopropylphenyl)-N=-aryl ureas (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14).) and N-(ortho-cyclopropylphenyl)-N=-aryl thioureas (15)(16)(17)(18)(19)(20)(21)(22)(23), structurally related to the earlier studied acetamides [6] and benzamides [4,5].…”

“…Consequently, besides formation of oxazine and thiazine structures (A 1 and A 2 ), other mechanisms of rearrangement of M ϩ· should be taken into account (see below). As a rule the most abundant peak in EI mass spectra of substituted N-(ortho-cyclopropylphenyl)-N=-arylureas and thioureas corresponds to the [M Ϫ 28] ϩ· ion°(Table°1,°Figure°1b).°Formation°of°ArNH 2 ϩ· ions is another°important°process°(Figure°1a)°in°the°case°of ureas°1-15 [13].…”

“…Mass spectrometry allows for the prediction of monomolecular reactions of the substituted N-(orthocyclopropylphenyl)-N=-aryl ureas (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) and N-(orthocyclopropylphenyl)-N=-arylthioureas (15-23) catalyzed by acids in solution. Two model compounds, (1 and 15), were subjected to the acid catalyzed cyclization.…”

“…2. Interaction of the substituted N-(ortho-cyclopropylphenyl)-N=-aryl ureas (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)) and N-(ortho-cyclopropylphenyl)-N=-aryl thioureas (15)(16)(17)(18)(19)(20)(21)(22)(23)) with strong acids is a convenient method for synthesis of substituted benzoxazines and benzothiazines.…”

“…Substituted N-(ortho-cyclopropylphenyl)-N=-aryl ureas (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) and N-(ortho-cyclopropylphenyl)-N=-aryl thioureas (15)(16)(17)(18)(19)(20)(21)(22)(23) possess four nucleophilic sites [N, N=, O (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) or S (15)(16)(17)(18)(19)(20)(21)(22)(23), and the ortho-position of the aromatic ring attached to N=], which are able to attack the charged cyclopropyl moiety. Therefore, at least four heterocycles (P 1 -P 4 ) can be formed in the intramolecular cyclization reaction.…”