Heterocyclic compounds mass spectroscopy

Although several metal-containing heterocyclic compounds (such as porphyrins, phthalocyanines, naphthenates) are present in oil fractions most of the bench-scale research has been based on relatively rapid Ni, V, or Ni/V deposition procedures in which experimental FCC formulations have been artificially metal contaminated with solutions of Ni and/or V naphthenate dissolved in benzene (or toluene) (24). Metal levels in these novel FCC are usually above 0.5% that is well above the concentration that today exist on equilibrium FCC, see Figure 1. High metal concentration facilitate the study and characterization of Ni and V effects by modern characterization techniques such as X-ray photoelectron spectroscopy (XPS), Laser Raman spectroscopy (LRS), X-ray diffraction (XRD), electron microscopy, secondary ion mass spectrometry (SIMS), and 51V nuclear magnetic resonance (NMR). 

A few excellent reviews appeared recently on the structure of the nitro group and the spectroscopy of nitro compounds [ 1 -5 ] including mass spectroscopy of nitro derivatives of arenes and heterocycles reviewed by Khmelnitskii and Terentyev (145] and particularly on the C—NO2 bond [3j. Thus only some problems related to the nitro group will be given here. 

Furazano[3,4-/]quinoxaline, 7,8-diphenyl-synthesis, 6, 412 Furazanothiophene synthesis, 6, 417 Furazans, 6, 393-426 biological activity, 6, 425 bond angles, 6, 396 bond lengths, 6, 396 coordination compounds, 6, 403 diamagnetic susceptibilities, 6, 395 dipole moments, 6, 395, 400 heats of combustion, 6, 400 heterocyclic ring reactions, 6, 400-403 IR spectra, 6, 398 isoxazoles from, 6, 81 mass spectra, 6, 399 microwave spectroscopy, 6, 395, 396 MO calculations, 6, 395 monosubstituted... 

The format of this section is similar to that of the review by Knowles <1996CHEC-II(7)489>, where only the main structure elucidation techniques are reviewed. None of the heterocyclic systems included in this chapter exists as radicals thus, electron spin resonance (ESR) spectroscopy is not included. Mass spectrometry is also omitted from discussion, as this technique is always used in conjunction with other analytical techniques to ensure full characterization of compounds. Nevertheless, mass spectra for most of the compounds in this chapter have been reported, although assignments of fragmentation patterns are rarely given. 

Three new alkaloids, euthyroideones A, B and C (11-13) were isolated from the New Zealand bryozoan Euthyroides episcopalis [38]. All three compounds contain the unique heterocyclic pyrido(4,3-h)-l,4-benzothiazine skeleton. The structure of euthyroideone A (11) was determined by X-ray crystallography, NMR spectroscopy and mass spectrometry. Euthyroideone B (12) exhibited modest cytotoxicity against the BSC-1 cell line [38],... 

Reactions of 5f/-2-methyl-l,2,4-triazepino[2,3- ]benzimidazol-4-one 71, prepared by reaction of 1,2-diaminobenz-imidazole 72 with acetoacetic ester 73, with different reagents was described, in the search of new heterocycles with biological activity <2002CHE598>. When lactam 71 was treated with aromatic aldehydes in boiling 1-BuOH with addition of piperidine 74, 577-3-arylidene-2-methyl-l,2,4-triazepino[2,3- ]benzimidazol-4-ones 75a-c were obtained (Scheme 7). Coupling lactam 71 with phenyldiazonium chloride 76 in dioxane afforded the 3-phenylazo-substituted tricycle 77. When 71 was treated with phosphorus pentasulfide 78 in boiling dioxane or pyridine, its thio analog 79 was obtained. The reaction proceeded most efficiently when lactam 71 was refluxed with twofold excess of 78 in dry dioxane. These thiones 79 react with ammonia and amines by nucleophilic substitution. When 79 was refluxed with ammonia, benzylamine, piperidine, or morpholine, the 4-amino-substituted tricycles 80a-d were obtained. All the described compounds were identified by NMR, mass spectrometry, and IR spectroscopy. 

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