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1.
Mass spectra of some selenides, sulphides and ethers of furan, thiophene and selenophene series are described. A new fragmentation reaction, consisting in splitting off alkyl, insertion of heteroatom in the cycle and loss of one of heteroatoms as C?X, is discussed in detail.  相似文献   

2.
Abstract— Oxygenated aqueous solutions of methylene blue containing dispersions of sodium dodecyl sulphate micelles with solubilised diphenyl isobenzofuran were irradiated with red light and the rate of loss of furan was followed over several min. The results are consistent with a mechanism in which singlet oxygen is produced by energy transfer from methylene blue triplet in the aqueous phase, and then diffuses to and penetrates the interior of the micelles where it reacts with the furan. The competition between this process and the natural decay of the excited oxygen has been examined and a β-value of 9.7 times 10-5 M determined which is comparable to that for the same reaction in homogeneous solvents. A model of the system is proposed and its kinetic features discussed.  相似文献   

3.
Data on methods for the production of furan and thiophene aldoximes, ketoximes, and amidoximes and their reactions are reviewed. The synthesis of new heterocycles from furan and thiophene oximes and the biological activity of derivatives of the oximes are discussed individually.  相似文献   

4.
A convenient new method for the arylation of furan with derivatives of diazoaminobenzene and isoamyl nitrite is described. Using this method the substituted 2-(X-phenyl)furan derivatives, where X is H, 4-CH3, 4-Cl, 4-Br, 3-Cl, 3,4-diCl, 4-NO2, 4-COOCH3, 4-COOH, 4-Cl-3-CF3 and 2-(3-pyridyl)furan were prepared. The reaction of methyl 4-aminobenzoate with furan and isopentyl nitrite gave (besides 2-(4-carbmethoxyphenyl)furan) 4,4′-dicarbmethoxydiazoaminobenzene, the structure of which was proved by mass spectrometry and by synthesis. This diazoaminobenzene derivative was unstable in the reaction medium and with isopentyl nitrite and furan at 30° gave 2-(4-carbmethoxyphenyl)furan. The mechanism of the reaction is discussed.  相似文献   

5.
The efficiency of three furan derivatives, namely 2-(p-toluidinylmethyl)-5-methyl furan (Inh. A), 2-(p-toluidinylmethyl)-5-nitro furan (Inh. B) and 2-(p-toluidinylmethyl)-5-bromo furan (Inh. C), as possible corrosion inhibitors for mild steel in 1.0 M HCl, has been determined by weight loss and electrochemical measurements. These compounds inhibit corrosion even at very low concentrations, and 2-(p-toluidinylmethyl)-5-methyl furan (Inh. A) is the best inhibitor. Polarization curves indicate that all compounds are mixed-type inhibitors, affecting both cathodic and anodic corrosion currents. Adsorption of furan derivatives on the mild steel surface follows the Langmuir adsorption isotherm, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. Monte Carlo simulations technique incorporating molecular mechanics and molecular dynamics can be used to simulate the adsorption of furan derivatives on mild steel surface in 1.0 M HCl.  相似文献   

6.
The 70-eV electron impact mass spectra of a series of thirty anthracene, seven anthra[2,1-b]furan and seven 2-nitroanthra[2,1-b]furan derivatives are described and discussed. A collisional activation dissociation study of 1-formyl-2,6-dimethoxy-9-methyianthracene, 1-formyl-2,6-dimethoxy-10-methylanthracene, and 2-carboxy-11-methylanthra[2,1-b]furan has been carried out using tandem mass spectrometry in order to substantiate the fragmentation schemes.  相似文献   

7.
The ionic liquid 1-butyl-3-methyl-imidazolium hydrogen sulfate, [bmim]HSO4, efficiently catalyzes Paal–Knorr furan synthesis without any organic solvent. A wide range of aliphatic and aromatic 1,4-diketones easily undergo condensations to form furan derivatives, providing a general and convenient procedure. The Paal–Knorr reaction of ester-substituted 1,4-diketones is first reported. The ionic liquid can be recovered and reused for subsequent runs without any appreciable loss of efficiency.  相似文献   

8.
The microwave spectra of furan, [2-D], [3-D] and [2,5-D2] furans have been reinvestigated. Also the spectrum of [D4]furan was assigned and measured. Determination of atomic coordinates by mono- and disubstitution is discussed. The complete substitution structure has been redetermined confirming results of earlier work.  相似文献   

9.
The K-shell spectra of gaseous 2,5-dihydrofuran at the carbon and oxygen thresholds are reported for the first time. They have been measured using the inner-shell electron energy loss spectroscopy (ISEELS) method. Ab initio Configuration Interaction calculations have been carried out to assign the observed bands. The O1s spectrum is similar to that of tetrahydrofuran and the assignments of the bands are close to those obtained in the case of furan, excepting the furan first π* band. At the C1s edge, the spectrum differs from the furan case, because of the different chemical environment of one of the non-equivalent carbon atoms: due to the presence of hydrogen atoms out of the carbon–oxygen ring plane, several Rydberg core excited states have an important valence character, leading to large intensities in the experimental spectrum.  相似文献   

10.
汪志峰  徐凡  沈琪 《化学研究与应用》2007,19(12):1353-1355
D iels-A lder反应具有立体专一性和很好的区域选择性,已被大量应用于天然有机化合物、香料、药物等的合成中。一般说来,D iels-A lder反应在加热条件下即能发生,但加热往往导致反应的区域选择性和立体专一性下降,而研究表明,路易斯酸催化下的D iels-A lder反应在不同程度上表现出或反应速度加快,或产率提高,或条件温和,尤其是区域选择性和立体专一性得到提高等良好特性。呋喃类化合物由于呋喃环所具有的芳香性而较难与一般的亲双烯发生D iels-A lder反应。如呋喃和丙烯酸甲酯在加热条件下反应2~3个月,产率只能达到50%,且反应温度的提高…  相似文献   

11.
We have synthesized sterically strained conjugated systems containing a trisubstituted furan ring. We have used X-ray diffraction to study the three-dimensional structure of 5-dimethylamino-2,4-bis[(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)methyl]furan. We have shown that such sterically strained systems undergo nonclassical deformations with distortion of mainly bond angles, but without loss of planarity.Kuban State Technological University, Krasnodar 350072, Russia; e-mail: organiscs@kubstu.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1476–1484, November, 1999.  相似文献   

12.
A series of heterocyclic liquid crystalline compounds containing 1,3,4-oxadiazole/thiadiazole, furan and thiophene units were synthesised and characterised by means of electrospray ionisation-mass spectrometry (ESI-MS), high-resolution mass spectroscopy (HRMS), 1H nuclear magnetic resonance (NMR) and 13C NMR. The thermal behaviours were investigated by differential scanning calorimetry (DSC) and polarised optical microscopy (POM). The effect of the 1,3,4-oxadiazole, 1,3,4-thiadiazole, furan, thiophene and benzene rings on the liquid crystalline properties was discussed briefly in context with the geometrical and electronic factors. The results showed that the tendency to form mesophases follows the sequence: 1,4-disustituted benzene >2,5-disubstituted thiophene >2,5-disustituted furan and 1,3,4-thiadiazole >1,3,4-oxadiazole.  相似文献   

13.
Published data and the results of the authors’ own investigations on the catalytic oxidation of furan and its homologs under various conditions are reviewed. The mechanisms and the characteristics and composition of the products from the transformations of furans are discussed in relation to the type of oxidizing agent and the reaction conditions. The prospects of using the oxidation processes of furan and its homologs in the synthesis of alkoxy- and dialkoxydihydrofurans, 5-alkoxy-2(5H)-furanones, β-formylacrylic acid, maleic acid, and its dialdehyde are indicated.  相似文献   

14.
葛子义 《高分子科学》2017,35(2):171-183
Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.  相似文献   

15.
Furfural derived from biomass hemicelluloses is an important intermediate for biofuels and chemicals. In order to further upgrade, furfural is usually reduced into 2-methyl furan that is more stable and useful. In this work, furfural was reduced by CuZnAl, CuMgAl, Cu2Cr2O5, CuNiAl as catalysts in a supercritical methanol without external H2 source. The best yield of 2-methyl furan was achieved among the H2 free furfural process reported as high as 74%. And the catalytic behaviors were discussed under difierent catalysts and temperatures conditions.  相似文献   

16.
The MCD spectra of pyrrole, furan, thiophene, selenophene and teburophene and some of their derivatives are reported and the corresponding energies, oscillator strengths, transition moment directions, and MCD terms are calculated from semi-empirical quantum mechanical calculations hi the π-electron approximation. The MCD spectrum of thiophene is only slightly perturbed by substituents, and this is also expected to be true of the quite similar MCD spectra of selenophene and tellurophene. These molecules can then be classified as “hard” chromophores. On the other hand, pyrrole and furan have different and much weaker MCD spectra which change shape considerably when substituents are introduced. The implications of these observations are further discussed.  相似文献   

17.
氮气气氛下,以TN型液晶为实验材料,利用TGA-FTIR联用仪研究热解失重特征及过程产物;同时利用GC-MS对管式炉实验系统热解产物进行分析。结果表明,TN型液晶热解失重起始温度为120℃,剧烈失重温度为220℃~430℃;热解产物除了含CO2外,还含有1~5个碳原子官能团的苯、苯酚、苯呋喃等组成的芳香族化合物、多环芳烃以及丙烷为主的烃类有机物。这些有机物绝大多数是有毒有害物质,可进一步通过焚烧热解产物来实现TN型废液晶无害化处理。  相似文献   

18.
The interactions of furan, pyrrole and N-methyl pyrrole with electrophiles have been investigated by means of the calculated molecular electrostatic potentials, obtained from INDO wave functions, which indicate the most attractive sites and pathways of attack for an approaching electrophile. The very distinct preference of these heterocycles for α-substitution can be interpreted quite satisfactorily in the case of furan if it is assumed that the α-hydrogen moves out of the plane of the molecule, forming a quasi-tetrahedral carbon, as an initial step in the reaction. For pyrrole and N-methyl pyrrole it is found to be necessary to invoke out-of-plane “bending” of the N-H, N-CH3 and Cα-Hα bonds to explain both the preference for α-substitution, and also the relative selectivities of furan, pyrrole and N-methyl pyrrole. The energies, atomic charges and bond orders of various forms of these heterocycles are also discussed.  相似文献   

19.
Triphenylphosphine inserts into the peroxide bond of 1,2-dioxines, initiating ring contraction with loss of triphenylphosphine oxide. This process yields dihydrofuran oxides in 54-97% yield from oxirenyl[2,3-c][1,2]dioxines and dihydrofurans from 3,6-dihydro-1,2-dioxines with inversion of stereochemistry at either the 2 or 5 position in the furan product.  相似文献   

20.
Formic solutions of ADCA react with cyclic and heterocyclic conjugated dienes affording the Diels-Alder 1 or pseudo-Michael 2 adducts depending on the nature of the diene. Generalisation to RCCCHO and furan shows a similar behaviour (RCO2,Et, H) and a third possible pathway (electr. subst. of CO on α of furan,RAr, Alk); mechanisms are discussed.  相似文献   

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