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1.
The electrochemical oxidation of catechols (1a-c) has been studied in the presence of 6-methyl-1,2,4-triazine-3-thion-5-one 3 in aqueous sodium acetate, using cyclic voltammetry and controlled-potential coulometry. A plausible mechanism for the oxidation of catechols and their reaction with 3 is presented. All the catechol derivatives (1a-c) were converted into 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives (6a-c) through a Michael-type addition reaction of 3 to anodically generated o-quinones. The electrochemical syntheses of 6a-c were successfully performed in one pot in an undivided cell using an environmentally friendly method with high atomic economy. 相似文献
2.
Anodic oxidation of catechols 1a-e in the presence of 5-methyl-2-mercapto-1,3,4-thiadiazole 2 has been studied in acetate buffer solution by cyclic voltammetry and controlled-potential electrolysis techniques. The effects of various electrolytic conditions (amount of passed charge, anodic materials, pH of the electrolytic solution, applied potential, and concentration of substrates) on the yield have also been investigated. The results showed that the position of the initial substituent of the starting catechol derivatives dominated the formation of monothiadiazol-2-ylthio-substituted or/and dithiadiazol-2-ylthio-substituted products. For 4-substituted catechols 1a-b, monothiadiazol-2-ylthio-substituted products (3a-b) were exclusively produced in high to excellent yields. However, in the cases of catechol itself (1c) and 3-substituted catechols (1d-e), both monothiadiazol-2-yl-substituted (3c-e and 5d-e) and dithiadiazol-2-ylthio-substituted products (4c-e) were isolated. In addition, the nature of the initial substituent of the starting 3-substituted catechols (1d and 1e) affected the relative ratio of the two monothiadiazol-2-ylthio-substituted isomers (3d-e vs 5d-e). 相似文献
3.
Rachid Skouta 《Tetrahedron letters》2007,48(47):8343-8346
(±)-Pterocarpan and analogues (4a-c) have been synthesized efficiently via the annulation of salicylaldehydes (1a, 1b and 1c) and o-methoxymethoxylphenylacetylene (2a), followed by a one-pot reduction and acidic cyclization of the ketones (3a-c). In addition, isoflavone derivatives (5a-c) have been synthesized rapidly, in two steps, via the annulation of salicylaldehyde (1a) and arylacetylenes (2b, 2c and 2d), followed by IBX/DMSO oxidation of the isoflavanones (3d, 3e and 3f). 相似文献
4.
Saied Saeed Hosseiny Davarani Neda Sheijooni Fumani Farzaneh Moradi 《Tetrahedron letters》2008,49(4):710-714
Electrochemical oxidation of several catechols is studied in the presence of 4(6)-aminouracil (3a) and 6-amino-1,3-dimethyl uracil (3b) as nucleophiles in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results reveal that quinones derived from catechols participate in Michael additions with 3a and 3b to give the corresponding catecholamine derivatives via an electron transfer followed by chemical reaction (EC) mechanistic pathway in good yields and purities. 相似文献
5.
Shin-ichi NayaMakoto Nitta 《Tetrahedron》2003,59(21):3709-3718
Novel condensation reaction of tropone with N-substituted and N,N′-disubstitued barbituric acids in Ac2O afforded 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (8a-f) in moderate to good yields. The 13C NMR spectral study of 8a-f revealed that the contribution of zwitterionic resonance structures is less important as compared with that of 8,8-dicyanoheptafulvene. The rotational barriers (ΔG‡) around the exocyclic double bond of mono-substituted derivatives 8a-c were obtained to be 14.51-15.03 kcal mol−1 by the variable temperature 1H NMR measurements. The electrochemical properties of 8a-f were also studied by CV measurement. Upon treatment with DDQ, 8a-c underwent oxidative cyclization to give two products, 7 and 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates (11a-c·BF4− and 12a-c·BF4−) in various ratios, while that of disubstituted derivatives 8d-f afforded 7,9-disubstituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (11d-f·BF4−) in good yields. Similarly, preparation of known 5-(1′-oxocycloheptatrien-2′-yl)-pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (14a-d) and novel derivatives 14e,f was carried out. Treatment of 14a-c with aq. HBF4/Ac2O afforded two kinds of novel products 11a-c·BF4− and 12a,c·BF4− in various ratios, respectively, while that of 14d-f afforded 11d-f. The product ratios of 11a-c·BF4− and 12a-c·BF4− observed in two kinds of cyclization reactions were rationalized on the basis of MO calculations of model compounds 20a and 21a. The spectroscopic and electrochemical properties of 11a-f·BF4− and 12a-c·BF4− were studied, and structural characterization of 11c·BF4− based on the X-ray crystal analysis and MO calculation was also performed. 相似文献
6.
Electrochemical oxidation of catechols 1a-d has been studied in the presence of 4-amino-6-methyl-1,2,4-triazine-3-thion-5-one 3 as a nucleophile in aqueous solutions, using cyclic voltammetry and controlled-potential coulometry, leading to the efficient synthesis of 1,2,4-triazino[3,4-b]-1,3,4-thiadiazines. 相似文献
7.
The reaction of 2-hydrazino-3-methylquinoxaline 1 with trifluoromethyl-β-diketones 2 not only yields the expected 5-trifluoromethyl-5-hydroxy-Δ2-pyrazolines 3a-3f and/or 3-trifluoromethylpyrazoles 4c-4f but also the unexpected products 1,2,4-triazolo[4,3-a]quinoxalines 5a-5f and/or 3(5)-trifluoromethyl-1H-pyrazoles 6c-6f. Furthermore, the acid-catalyzed dehydration of 5-hydroxypyrazolines 3a-3b resulted in the formation of unexpected 5a-5b along with the expected corresponding pyrazoles 7a-7b. These unprecedented observations provide evidence for the existence of equilibrium between the hydroxypyrazoline 3 and its open chain tautomer, ketoimine 9 in the mechanistic path leading to the formation of pyrazoles 7 and triazoles 5. 相似文献
8.
Moonhyun Oh 《Journal of organometallic chemistry》2003,687(1):78-84
The cationic manganese tricarbonyl complexes containing η6-2-methylhydroquinone (2a), η6-2,3-dimethylhydroquinone (3a), η6-2-t-butylhydroquinone (4a), η6-tetramethylhydroquinone (5a) and η6-4,4′-biphenol (6a) are readily deprotonated to the corresponding neutral (η5-semiquinone)Mn(CO)3 (2b-6b) and anionic (η4-quinone)Mn(CO)3− (2c-5c) complexes. The X-ray structures of 2b-6b feature strong intermolecular hydrogen bonding interactions that result in the formation of supramolecular organometallic networks. Significantly, the substitution pattern at the semiquinone ring affects the stereochemistry of the hydrogen bonding interactions. NMR spectra of 2b, 3b and 5b reveal dynamic hydrogen bonding in solution. 相似文献
9.
The natural flavors 2-acetyl-1-pyrroline 1a, 2-propionyl-1-pyrroline 1b, 2-acetyl-3,4,5,6-tetrahydropyridine 1c, 2-acetyl-2-thiazoline 1d, 2-propionyl-2-thiazoline 1e, and the artificial flavor 2-acetyl-5,6-dihydro-4H-1,3-thiazine 1f have been prepared by catalytic SeO2 oxidation of the corresponding cyclic imines 6a-c and sulfur cyclic imines 7a-c using TBHP as co-oxidant. The oxidation of the pyrrolines 1a and b is completely regioselective. Professional olfactory evaluation together with the odor threshold of the new flavor 1f is reported. 相似文献
10.
Saied Saeed Hosseiny Davarani Ali Reza Fakhari Ahmad Shaabani Hamid Ahmar Ali Maleki Neda Sheijooni Fumani 《Tetrahedron letters》2008,49(39):5622-5624
Electrochemical oxidation of 2,3-dimethylhydroquinone 1 has been studied in the presence of o-phenylenediamines 3a-c as nucleophiles in aqueous solution, using cyclic voltammetry and controlled potential coulometry. The results indicate that the quinone 2 derived from 2,3-dimethylhydroquinone participates in Michael addition and imine condensation reactions with o-phenylenediamine via an ECECC mechanism, and is converted to the corresponding phenazine derivatives 7a-c and 7′b. The electrochemical synthesis of compounds 7a-c and 7′b has been performed successfully at a carbon rod electrode in an undivided cell with good yields and high purities. 相似文献
11.
Palladium catalyzed cross-coupling of 3-amino- and 3-acylamido-2-bromopyridines 1a-f with triethyl phosphite allowed the synthesis of 3-amino- and 3-acylamido pyridine-2-phosphonic acid diethyl esters 2a-f, whereas nickel catalysts, although providing access to related anilido-2-phosphonates, proved inactive. Reduction of the aminophosphonate 2a with LiAlH4 afforded 3-amino-2-phosphinopyridine (3a), which was cyclocondensed with dimethylformamide dimethyl acetal (DMFA) via phosphaalkene intermediates 4a to the novel pyrido[b]-anellated 1,3-azaphosphole 5a. Reaction of amidophosphonates 2b-f with LiAlH4 did not result in the expected reductive cyclization, as shown by closely related anilido-2-phosphonates, but led to product mixtures containing N-secondary 3-amino-2-phosphinopyridines 3b-f as the main or major component. The conversion of 3b,d,e with DMFA to 5b,d,e provides first examples of N-substituted pyrido[b]-anellated azaphospholes. Structures were confirmed by multinuclear NMR and X-ray crystallography (for 2c, 3b). 相似文献
12.
Reaction of 19-hydroxyandrosta-4,6-diene-3,17-dione (8b) and the corresponding Δ7-compound (8c) with diethyl-(2-chloro-1,1,2-trifluoroethyl)-amine affords 5β,19-cyclo-Δ1,6- and 5β,19-cyclo-Δ1,7-3-ketones (4b) and (4c) respectively. Solvolysis experiments with the 19-tosylates of the 19-hydroxy-Δ4,6- and Δ4,7-3-ketones (8b) and 8c) are described as alternate approaches to (4b) and (4c). Exposure of 5β,19-cyclo compounds (4b) and (4c) to acetic anhydride-acetic acid-p-toluenesulfonic acid yields the respective 3-acetoxycycloheptatrienes (5a) and (6a). The latter substance (6a) is converted into the novel tetracyclic 1,6-methano-[10]annulene (2a) on exposure to N-bromosuccinimide in boiling carbon tetrachloride. Synthesis of the corresponding 3-methoxy- and 3-desoxy-1,6-methano-[10]annulenes (2b) and (2c) are also described. The NMR spectra of (2a), (2b) and (2c) and related intermediates are discussed. 相似文献
13.
A novel synthesis of polysubstituted pyrazoles 3a-d, pyrimidines 4a-f and quinolines 5a-c via the reaction of α,α-oxoketene dithioacetals 2a-c with hydrazine hydrate, malonohydrazide, urea, thiourea and aniline is reported and the synthetic potential of the method is demonstrated. The structure of the new compounds was established upon their elemental analysis, IR, 1H NMR and 13C NMR. 相似文献
14.
Shin-ichi Naya 《Tetrahedron》2005,61(36):8616-8624
The synthesis and properties of a novel type of 5-[bis(1-heteroazulen-3-yl)methylidene]pyrimidine-2,4,6(1,3,5H)-triones (13a-c) and (14a-c) are studied. The synthetic procedure is based on addition of bis(1-heteroazulen-3-yl)methyl cations with barbituric acid and subsequent oxidation by o-chloranil. Structural characteristics of 13a-c and 14a-c were clarified on inspection of the 13C NMR spectral data and X-ray crystal analysis. Based on the investigation of the UV-vis spectra of 13a-c and 14a-c and their protonated cations, conformational change of the heteroazulene-moiety and the barbituric acid-moiety is suggested. In the CV measurements of 13a-c and 14a-c, two reversible reduction waves are observed, indicating the stabilizing ability of heteroazulenes toward the corresponding radical and anion species. Furthermore, 13a-c and 14a-c exhibit one irreversible oxidation wave and the corresponding reduction wave appearing in a far negative region, which suggested a conformational change in the radical cation during the redox process. The conformational change is rationalized on the basis of the MO calculations. 相似文献
15.
An efficient non-reductive synthesis of 3-aminomethylindole (6) was developed from gramine (1) via 3-phthalimidomethylindole (2). The reactions of amine 6 with substituted methyl dithiobenzoates gave 3-(arylthiocarbonylaminomethyl)indoles. The Hugerschoff ring-closure reactions of the thiobenzamide intermediates (11a-f) with phenyltrimethylammonium tribromide and subsequent basic treatment furnished 2-arylthiazino[6,5-b]indole derivatives (14a-f). By use of the latter bromine source, the phytoalexin cyclobrassinin (8) was prepared in a considerably higher yield than described previously. The structures of the novel products were elucidated by IR, 1H and 13C NMR spectroscopy, including 2D-HMQC, 2D-HMBC and DEPT measurements. 相似文献
16.
María del Carmen Cruz 《Tetrahedron》2005,61(42):10061-10072
The intramolecular cyclization of the β-substituted olefins methyl 2-aryloxy-3-dimethylaminopropenoates 3a-3f catalyzed by Lewis acids leads to a short and novel synthesis of benzofurans 2a-2f. When the olefins 4-dimethylamino-3-aryloxy-3-buten-2-ones 4a-4f were used, the cyclization process was faster and provided the corresponding substituted 2-acetylbenzofurans 1a-1f. Among the latter, naturally occurring compounds calebertin (1a), caleprunin A (1b), and caleprunin B (1c) were prepared in good overall yields. These benzofurans were also obtained by direct treatment under MW irradiation of the precursors 1-aryloxypropan-2-ones 7a-7c with DMFDMA, followed by addition of the catalyst, resulting in a route that was one step shorter. 相似文献
17.
Faramarz Rostami Charati Malek Taher Maghsoodlou Sayyed Mostafa Habibi Khorassani 《Tetrahedron letters》2008,49(2):343-347
A facile diastereoselective synthesis of highly functionalised 3-(1-diphenylphosphonylethyl)butyrolactone analogues, 3a-c is achieved from the reaction of dialkyl acetylenedicarboxylates, 2a,b, with thiolated and trifluoromethylated-1,3-diones, CH acids, 1a,b, in the presence of triphenyl phosphite. The resulting products, 3a-c, are obtained in high yields and characterised by 1H/13C, 19F, 31P NMR and X-ray crystallography. 相似文献
18.
Shin-ichi Naya 《Tetrahedron》2005,61(21):4919-4930
Novel photo-induced oxidative cyclization was accomplished to synthesize areno[b]pyrimido[5,4-e]pyran-2,4(1,3H)-dionylium ions 13a-c+·ClO4−. Furthermore, 13a-c+·BF4− and their phenyl-substituted derivatives 19a,b+·BF4− were alternatively synthesized by the reaction of salicylaldehyde and its naphthyl derivatives with barbituric acids and subsequent treatment with aq. HBF4. Structural characteristics of 13a-c+ and 19a,b+ were clarified on inspection of the UV-vis and NMR spectral data as well as X-ray crystal analyses. The electrochemical properties were studied by the CV measurement. In a search for reactivity, reactions of 13a-c+·BF4− with some nucleophiles, hydride, benzylamine, and H2O, were also carried out. The photo-induced autorecycling oxidation reactions of 13a-c+·BF4− toward some amines under aerobic conditions were carried out to give the corresponding imines (isolated by converting to the corresponding 2,4-dinitrophenylhydrazones) in 643-3600% yield (recycling number of 13a-c+·BF4−: 6.4-36.0). 相似文献
19.
Ashok K.S. Chauhan Arun Kumar Jens Beckmann Ray J. Butcher 《Journal of organometallic chemistry》2004,689(2):345-351
Bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YC6H4COCH2)2TeBr2, (Y=H (1a), Me (1b), MeO (1c)) can be prepared either by direct insertion of elemental Te across CRf-Br bonds (where CRf refers to α-carbon of a functionalized organic moiety) or by the oxidative addition of bromine to (p-YC6H4COCH2)2Te (Y=H (2a), Me (2b), MeO (2c)). Bis(p-substituted benzoylmethyl)tellurium dichlorides, (p-YC6H4COCH2)2TeCl2 (Y=H (3a), Me (3b), MeO (3c)), are prepared by the reaction of the bis(p-substituted benzoylmethyl)tellurides 2a-c with SO2Cl2, whereas the corresponding diiodides (p-YC6H4COCH2)2TeI2 (Y=H (4a), Me (4b), MeO (4c)) can be obtained by the metathetical reaction of 1a-c with KI, or alternatively, by the oxidative addition of iodine to 2a-c. The reaction of 2a-c with allyl bromide affords the diorganotellurium dibromides 1a-c, rather than the expected triorganotelluronium bromides. Compounds 1-4 were characterized by elemental analyses, IR spectroscopy, 1H, 13C and 125Te NMR spectroscopy (solution and solid-state) and in case of 1c also by X-ray crystallography. (p-MeOC6H4COCH2)2TeBr2 (1c) provides, a rare example, among organotellurium compounds, of a supramolecular architecture, where C-H-O hydrogen bonds appear to be the non-covalent intermolecular associative force that dominates the crystal packing. 相似文献
20.
Biswajit Deb Kokil Saikia Rebecca A.M. Randall J. Derek Woollins 《Journal of organometallic chemistry》2011,696(20):3279-3283
The reaction of [Rh(CO)2Cl]2 with 0.5 mol equivalent of the ligands [P′(X)(CH2-CH2P(X)Ph2)3](P′P3X4) {where X = O(a), S(b) and Se(c)} affords tetranuclear complexes of the type [Rh4(CO)8Cl4(P′P3X4)] (1a-1c). The complexes 1a-1c have been characterized by elemental analyses, mass spectrometry, IR and multinuclear NMR spectroscopy, and the ligands b and c are structurally determined by single crystal X-ray diffraction. 1a-1c undergo oxidative addition (OA) reactions with CH3I to generate Rh(III) oxidised products. Kinetic data for the reaction of 1a and 1b with excess CH3I indicate a pseudo first order reaction. The catalytic activity of 1a-1c for the carbonylation of methanol to acetic acid and its ester show a higher Turn Over Frequency (TOF = 1349-1748 h−1) compared to the well-known species [Rh(CO)2I2]− (TOF = 1000 h−1) under the similar experimental conditions. However, 1b and 1c exhibit lower TOF than 1a, which may be due to the desulfurization and deselinization of the ligands in the respective complexes under the reaction conditions. 相似文献