Cyclization of ortho-cyclopropylphenyl benzamides in gas and liquid phases

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.     

Study of synthetic aliphatic copolyamides by time-of-flight matrix assisted laser desorption/ionization mass spectrometry

Synthetic copolyamides based on aliphatic diamines (1,3-propanediamine and 1,4-butanediamine) and dichlorides of aliphatic carboxylic acids (adipic and sebacic acid dichlorides) were investigated using time-of-flight matrix assisted laser desorption/ionization mass spectrometry. Their mass spectra showed peaks for cationized (Na⁺ and K⁺) and protonated (less intense peaks) oligomers with NH₂-NH₂, NH₂-COOH, or COOH-COOH end groups. No cyclic oligomers were detected in the samples. The compositions of oligomers were determined, and the relative reactivities of homologous comonomers in polycondensation were estimated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1320–1324, July, 2007.     

Charge Reversal Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

We report the first charge reversal experiments performed by tandem-in-time rather than tandem-in-space MS/MS. Precursor odd-electron anions from fullerene C₆₀, and even-electron ions from 2,7-di-tert-butylfluorene-9-carboxylic acid and 3,3′-bicarbazole were converted into positive product ions (^–CR⁺) inside the magnet of a Fourier transform ion cyclotron resonance mass spectrometer. Charge reversal was activated by irradiating precursor ions with high energy electrons or UV photons: the first reported use of those activation methods for charge reversal. We suggest that high energy electrons achieve charge reversal in one step as double electron transfer, whereas UV-activated ^–CR⁺ takes place stepwise through two single electron transfers and formally corresponds to a neutralization-reionization (^–NR⁺) experiment.      

Cyclization of the substituted <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">Ortho</Emphasis>-cyclopropylphenyl)-<Emphasis Type="Italic">N′</Emphasis>-aryl ureas and thioureas in the gas phase and solution

Electron ionization (EI), chemical ionization (CI), tandem mass spectrometry, high-resolution measurements, and labeling studies as well as quantum chemical calculations were used to understand the behavior of the molecular radical cations (EI) and protonated molecules (CI) of substituted N-(ortho-cyclopropylphenyl)-N'-aryl ureas and N-(ortho-cyclopropylphenyl)-N'-aryl thioureas in a mass spectrometer. Fragmentation schemes and possible mechanisms of primary isomerization were proposed. According to the fragmentation pattern, formation of the corresponding benzoxazines and benzothiazines was considered as the major process of isomerization of the original M(+.) and MH(+), although some portions of these ions definitely transformed into other structures. The treatment of N-(ortho-cyclopropylphenyl)-N'-phenyl urea and N-(ortho-cyclopropylphenyl)-N'-phenylthiourea in solution with strong acids formed predicted 4-ethyl-N-phenyl-4H-3,1-benzoxazin-2-amin and 4-ethyl-N-phenyl-4H-3,1-benzothiazin-2-amine as principal products.     

Cyclization of N,N-dialkylditiocarbamate and alkylxanthate derivatives of polyhalogenated pyridines in gas and liquid phases

The intramolecular cyclization of 31 polyhalogen substituted pyridines containing N,N-dialkyldithiocarbamate or alkylxanthate groups has been compared in reaction in solution with sodium N,N-dialkyldithiocarbamates or potassium carbetoxydithiolate and in the gas phase under electron ionization (EI). The scheme of fragmentation of the studied compounds has been proposed. An influence of the nature of leaving groups (Cl, F, CF(3), CN, COOEt), of the presence of electron withdrawing groups (Cl, F, CN, CCl(3), CF(3), COOEt) in ortho-,meta or para-positions to the leaving halogen, of the position of a dithio group toward pyridine nitrogen atom and of the role of oxygen and nitrogen in corresponding alkylxanthates and N,N-dialkyldithiocarbamates on the cyclization process has been investigated.     

Features of condensation of 4,4′-Dihydroxybiphenyl with phenylphosphonous tetraethyldiamide

4,4′-Dihydroxybiphenyl was condensed with phenylphosphonous tetraethyldiamide. The moleccular mass, chemical composition, and structural features of the product, oligo(4,4′-biphenylene phenylphosphonite), were elucidated using the method of matrix-activated laser desorption/ionization, with a time-of-flight (TOF) mass analyzer. The oligophenylphosphites containing labile P-N bond, which are unstable under conditions of recording mass spectra, were stabilized by conversion into oligophenylphosphonates. 1H-Tetrazole catalyzes the reaction of phenylphosphonous tetraethyldiamide with 4,4′-dihydroxybiphenyl. Cross-linking in the solid state of the oligo(4,4′-biphenylene phenylphosphonite) containing terminal phosphonamidite group leads to gradual increase in the molecular weight and is accompanied by redox processes.