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Relevant academic research and scientific papers

Derivatization of Secondary Amino Acids with 7-Nitro-4-benzofurazanyl Ethers

Five 7-nitro-4-benzofurazanyl ethers have been synthesized and their water solubilities and reactivities have been determined. 4-Methoxy-7-nitrobenzofurazan (NBD-OCH3) has a solubility similar to that of 4-chloro-7-nitrobenzofurazan (NBD-Cl) but reacts ca

Colorimetric analysis of malononitrile via the formation of a novel NBD-based CH-acidic dye

Malononitrile is a key starting material used in synthetic organic, medical, and industrial chemistry, but it is also a notorious cyanogenic toxicant. However, selective and sensitive analytical methods for this key chemical are rare. In this research, a

Colorimetric signaling of hydrogen sulfide by reduction of a phenylseleno-nitrobenzoxadiazole derivative

A new reaction-based probe for the colorimetric signaling of hydrogen sulfide was developed. Reduction of the nitro group of a nitrobenzoxadiazole moiety to an amino group resulted in pronounced chromogenic signaling in the form of a yellow to pink color change. The transformation of the nitro group to amino group was confirmed by the 1H NMR spectroscopy. The seleno derivative showed more efficient signaling behavior than the phenylthio and phenoxy analogues. Hydrogen sulfide signaling of phenylseleno- nitrobenzoxadiazole probe was fast and completed immediately after sample preparation. Selective signaling of hydrogen sulfide was possible in the presence of commonly encountered metal ions and anions with a detection limit of 2.1 × 10-6 M.

Kinetic and equilibrium studies of the reactions of 4-nitrobenzo-furazan and some derivatives with sulfite ions in water. Evidence for the Boulton-Katritzky rearrangement in a σ-adduct

The reactions with sulfite ions in water of 4-nitrobenzofurazan, 1, 4-nitrobenzofuroxan, 2, and three 4-nitro-7-substituted benzofurazans have been examined by 1H NMR spectroscopy and stopped-flow spectrophotometry. For each substrate the initial reaction occurs at the 5-position to give σ-adducts which have considerably higher thermodynamic stability than the corresponding adduct of 1,3,5-trinitrobenzene. In the cases of 1 and 2 isomerisation of the 5-adducts occurs slowly to yield adducts carrying sulfite at the 7-position. 1H NMR measurements on 2 labelled with 15N provide evidence that here the rearrangement involves an intramolecular Boulton-Katritzky mechanism.

Use of 4-nitro-2,1,3,-benzoxadiazole derivatives as dyes in colouring agents for keratin fibres

The object of the present invention is the use of 4-nitro-2,1,3-benzoxadiazole derivatives of general formula (I) as dye in colorants for keratin fibers such as, for example, wool, silk, furs or hair and particularly human hair In formula (I) X denotes ox

Effects of the substituent groups at the 4- and 7-positions on the fluorescence characteristics of benzofurazan compounds

To develop new fluorogenic reagents having the benzofurazan structure, we investigated the effects of the substituent groups at the 4- and 7-positions of the benzofurazan skeleton on the fluorescence characteristics (fluorescence intensity, maximum excitation wavelength and maximum emission wavelength). Seventy benzofurazan compounds substituted at the 4- and 7-positions were obtained for this purpose. The Hammett substituent constant (σp) was adopted as a parameter for electronic effects by substituent groups. The study using the sum and the difference of the Hammett substituent constants (σp) at the 4- and 7-positions revealed that the highly fluorescent benzofurazan compounds were classified into two groups and that singlet excitation energies, calculated by the maximum excitation and emission wavelengths, of the benzofurazan compounds were different between these two groups. The fluorescence characteristics of benzofurazan compounds substituted at the 4- and 7-positions were empirically predictable by these relationships and σp values. A new fluorogenic reagent, 4-phenylaminosulfonyl-7-fluoro-2,1,3-benzoxadiazole, for amines was developed based on this method and applied to the amino acids analysis.

Regioselectivity and Stereoelectronic Factors in the Reactions of Aryloxide Nucleophiles with 4-Nitrobenzofuroxan

The reactivity of 4-nitrobenzofuroxan (NBF, 1) with several aryloxide nucleophiles has been monitored by 400 MHz 1H NMR spectroscopy in acetonitrile-glyme (CD3CN-glyme, 1:1, v/v) at reduced temperatures and in dimethyl sulfoxide (DMSO) at ambient temperature.With the ambident (O- and C-) nucleophile phenoxide ion, formation of a C-7 O-adduct (3b) is observed in CD3CN-glyme at -40 deg C.As the temperature is raised this adduct gives way to 7-hydroxy-4-nitrobenzofurazan (as the anion, 5) and a 7-phenoxynitronate derivative (4b) that arises from transfer of the sp3-bound proton (7-H) of the C-7 phenoxide O-adduct to the N-oxide function.These decomposition products are the sole species observed when the reaction is carried out in DMSO.Thus in contrast to the reaction of 1 with methoxide ion, where the C-5 adduct (2a) is kinetically preferred while the C-7 adduct (3a) is thermodynamically more stable, no C-5 O-adduct of phenoxide is observed in the present system.In addition, C-adducts that could potentially arise from the ambident nature of phenoxide were not formed.A similar reaction sequence was found for the reaction of 1 with 3,5-di-tert-butylphenoxide ion and 2,4,6-trimethylphenoxide ion.However, C-attachment was observed in the reaction of 1 with 2,6-di-tert-butylphenoxide ion where O-attack is sterically blocked and, again, preference for C-7 attachment was found.Comparison is drawn between the present results concerning the reactivity of 1 with aryloxide nucleophiles and the reactivity displayed by methoxide ion.Stereoelectronic factors in the C-7 aryloxide O-adducts are also discussed.