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1.
The γ-alumina catalyzed synthesis of a new series of β-functionalized 5-methyl-1H-pyrazol-3-ol derivatives by the multi-component reaction of an aldehyde, ethylcyano acetate, and in situ generated 3-methyl-1H-pyrazol-5(4H)-one obtained from hydrazine monohyrade and ethyl acetoacetate in aqueous medium is described. The present reaction forms an important variant of the Yonemitsu-type multi-component reaction. The salient features of this present environmentally benign method are: recyclability of the catalysts, mild reaction condition, excellent yields of product, and the use of aqueous medium in the reaction.  相似文献   

2.
The halohydrin reaction of chiral N-enoyl-2-oxazolidinones 1 by halogen (Br2/I2) and water were efficiently carried out in aqueous organic solvent promoted by silver(I) with high anti- and regioselectivity and moderate to good diastereoselectivities. The alkenoyl, cinnamoyl and electron-deficient cinnamoyl substrates smoothly underwent bromohydrin reaction in aqueous acetone but no iodohydrin reaction, where as electron-rich cinnamoyl substrates preferred to undergo iodohydrin reaction in aqueous acetone with moderate diastereoselectivity and enhanced diastereoselectivity was observed in aqueous THF.  相似文献   

3.
Lei Shi  Feng Pan 《Tetrahedron》2008,64(11):2572-2575
Fully acetylated saccharides are inexpensive and very useful starting materials for the synthesis of many naturally occurring glycosides, oligosaccharides, and glycoconjugates. Ferric sulfate hydrate (Fe2(SO4)3·xH2O) was found to be a valuable Lewis acid promoter in the per-O-acetylation reaction of saccharides with acetic anhydride in 100% of conversion rate and 88-99% yields. Interestingly, the procedure is perfectly compatible with the presence of a variety of acid-labile protecting groups, such as isopropylidene, benzylidene, trityl, and TBDMS groups. The reactions were simply performed by stirring the mixture of a sugar with a slight excessive acetic anhydride in the presence of 2.0 mol % of Fe2(SO4)3·xH2O at rt and the pure products were obtained by a simple dilution of the reaction mixture with dichloromethane and washings with aqueous Na2CO3.  相似文献   

4.
A concise and stereocontrolled synthesis of rosuvastatin calcium has been accomplished, with the key steps including a Keck enantioselective allylation of chloroacetaldehyde with allyltributylstannane to install 5R-stereocenter and a VO(acac)2-catalyzed syn-diastereoselective epoxidation of (S)-1-chloropent-4-en-2-ol to set the requisite 3R-chirality.  相似文献   

5.
Arylaminotetrazole derivatives are synthesized efficiently by the reaction of arylcyanamides and sodium azide in the presence of ZnCl2 under aqueous conditions at reflux. Generally, isomer of 5-arylamino-1H-tetrazole can be obtained from arylcyanamides carrying electron-withdrawing substituent on aryl ring and as the electropositivity of substituent is increased, the product is shifted toward the isomer of 1-aryl-5-amino-1H-tetrazole.  相似文献   

6.
Diammonium hydrogen phosphate, (NH4)2HPO4(DAHP), efficiently catalyzes the one-pot, three-component reaction of an aromatic aldehyde, malononitrile and 4-hydroxycoumarin in aqueous media under mild conditions at room temperature, to afford the corresponding dihydropyrano[c]chromenes in high yields. (S)-Proline has also been used as another neutral catalyst for this reaction at reflux.  相似文献   

7.
We synthesized boron containing 2-(4-methoxybenzyl)-4-(4-(4,4,5,5-tetramethyl-1,3,2-dioaborolan-2-yl)phenyl) phthalazin-1(2H)-one 3 and 7-methyl-3-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-2H-benzo[b][1,4] oxazine 8. The reaction of compound 2 with B2pin2 using potassium acetate as the base and Pd(PPh3)2Cl2 as the catalyst, produced the corresponding boron-containing derivative 3 as a white solid in 65% yield. Alternatively, we have synthesized compound 8 as a yellow solid in 59% yield using the Miyaura borylation reaction. The potassium trifluoro(4-(-methyl-2H-benzo[b][1,4]oxazine-3-yl)phenylborate 9 was then obtained after treatment of 8 with aqueous solution of KF2H in methanol as white solid product in 60% yield. The biological activities of the synthetic compounds are currently being evaluated.  相似文献   

8.
16R-Bromopregnane-3S,20S-diol reacted with potassium t-butoxide to afford androst-16-en-3S-ol in a moderate yield via fragmentation reaction. The latter is a key intermediate for the synthesis of 5α-androst-16-en-3-one, as boar sex pheromone, and other steroidal drugs. In addition, 16R,20S-epoxypregnane-3S-ol was also obtained as a major product by changing the reaction solvent.  相似文献   

9.
Excess enthalpies of binary mixtures between each of alkane-1-amines {CnH2n+1NH2, n=3-8} and methyl methylthiomethyl sulfoxide (MMTSO) or dimethyl sulfoxide (DMSO) have been determined at 298.15 K. All mixtures showed positive enthalpy changes over the whole range of mole fractions.The limiting excess partial molar enthalpies of the aliphatic amines, H1E,∞, of all the mixtures with MMTSO or DMSO studied were smaller than those of MMTSO or DMSO, H2E,∞, respectively. Linear relations are obtained between limiting excess partial molar enthalpies and number of methylene groups.  相似文献   

10.
The superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids by Bronsted superacids (CF3SO3H, HSO3F) or strong Lewis acids AlX3 (X=Cl, Br) results in the formation of 4-aryl quinolin-2(1H)-ones in quantitative yields. The vinyl triflates or vinyl chlorides may be formed as additional reaction products. The investigated amides in reactions with benzene give 4,4-diaryl 3,4-dihydroquinolin-2-(1H)-ones under the superelectrophilic activation. 4-Aryl quinolin-2(1H)-ones in POCl3 are converted into 4-aryl 2-chloroquinolines. 4-Fluorophenyl-4-phenyl 3,4-dihydroquinolin-2-(1H)-one give N-formylation products in a yield of 79% under the Vilsmeier–Haack reaction conditions.  相似文献   

11.
N-Aryl substituted amides react with chlorodifluoromethane in the presence of concentrated aqueous sodium hydroxide and benzyltriethylammonium chloride (TEBAC) as a catalyst in benzene (phase-transfer catalysis, PTC), affording mixtures of N- and O-difluoromethyl substituted derivatives. Amide anions are involved in this process. The reaction carried out with oximes gives O-difluoromethyl oxime ethers.  相似文献   

12.
Summary. In the presence of DABCO, ethyl glyoxalate and (4S,5R)-1,5-dimethyl-3-acryloyl-4-phenylimidazolidin-2-one gave mixtures of the corresponding Baylis-Hillman adducts enriched in either isomer, depending on the absence or the presence of LiClO4 in the reaction mixture. A diastereomeric mixture in 10:90 dr allowed to definitively establish the mechanism of the reaction leading to trichloroacetamides starting from trichloroacetimidates of the Baylis-Hillman adducts.  相似文献   

13.
Rate constants, k A, for the aromatic nucleophilic substitution reaction of 2-chloro-3,5-dinitropyridine with aniline were determined in different compositions of 2-propanol mixed with hexane, benzene, and 2-methylpropan-2-ol and 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO4]) with dimethyl sulfoxide at 25°C. The obtained rate constants of the reaction in pure solvents are in the following order: 2-methylpropan-2-ol > dimethyl sulfoxide > 2-propanol > hexane > benzene > [Emim][EtSO4]. Molecularmicroscopic solvent parameters corresponding to the selected binary mixtures were utilized to study the kinetics of a nucleophilic substitution reaction in order to investigate and compare the effects of the solvents on a chemical process. The influence of solvent parameters including normalized polarity (E T N ), dipolarity/polarizability (π*), hydrogen bond donor acidity (α), and hydrogen bond acceptor basicity (β) on the second-order rate constants were investigated and multiple linear regressions gave much better results with regard to single parameter regressions. The dipolarity/polarizability of media has a positive effect in all mixtures regarding zwitterionic character of the reaction intermediate and the hydrogen bond acceptor basicity of the solvent by stabilizing of activated complex increases the reaction rate.  相似文献   

14.
The synthesis of imidazolidin-4-one derivatives of primaquine as potential antimalarial agents is described. The target compounds were synthesized in three steps: (i) condensation of (±)-primaquine with Nα-protected amino acids, (ii) removal of the Nα-protecting group, and (iii) reaction of the N-acylprimaquine with a carbonyl compound: acetone, three cyclic ketones and veratraldehyde. Using 2-formylbenzoic acid in the third step afforded 1H-imidazo[2,1-a]isoindole-2,5(3H,9bH)-diones. All products were isolated in good to excellent yields. Whereas imidazolidin-4-ones were formed as mixtures of all possible diastereomers in equal amounts, 1H-imidazo[2,1-a]isoindole-2,5(3H,9bH)-diones were produced in a stereoselective fashion. The compounds hydrolyse very slowly (t1/2 5-30 d) in pH 7.4 buffer to release primaquine. These primaquine derivatives are being submitted to biological assays, and preliminary results of their antimalarial activity are quite encouraging.  相似文献   

15.
The dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) was found to react with 2-(ROCH2)C5H4N (R =  Me, 2a; H, 2b) yielding a cationic mononuclear platina-β-diketone [Pt{(COMe)2H}{2-(MeOCH2)C5H4N}]Cl (3) and an acetyl(chloro)platinum(II) complex [Pt(COMe)Cl{2-(HOCH2)C5H4N}] (4), respectively. The reaction of 1 with 8-(methylthio)quinoline (5) resulted in the formation of [Pt(COMe)Cl{8-(MeS)C9H6N}] (6). The identities of all complexes were established by microanalysis, 1H, and 13C NMR spectroscopy. Single-crystal X-ray diffraction analysis showed 6 to be square-planar platinum(II) complex with N and C atoms as well as Cl and S atoms in mutually trans positions (configuration index: SP-4-2). In accordance with this, quantum chemical calculations on the DFT level of theory revealed a higher stability of complex 6 having a SP-4-2 configuration vs. the analogous complex in SP-4-3 configuration. The distinctly different reactivity of 1 with 2a on the one hand and with 2b and 5 on the other is discussed in terms of the HSAB concept and a deprotonation/reprotonation reaction.  相似文献   

16.
The efficient and simple routes for the synthesis of various ferrocenyl derivatives from ferrocenylcarbinols and N,N′-thiocarbonyldiimidazole (TCDI) are described. It involves grinding the two substrates in a Pyrex tube with a glass rod at room temperature. The reaction of ferrocenylmethanol (1a) provided S,S-bis(ferrocenylmethyl)dithiocarbonate (1b), whose crystal structure and a plausible mechanism for its formation are also reported. The reaction of 1-ferrocenyl-1-phenylmethanol (2a) and 1-ferrocenylbutanol (2b) gave the products 2c and 2d, respectively. The reaction of ω-ferrocenyl alcohols 4-ferrocenylphenol (3a) and 6-ferrocenylhexan-1-ol (3b) yielded the products 3c and 3d, respectively. Reaction of 1,1′-ferrocenedimethanol (3e) afforded 3f in moderate yield, and by contrast, it was not similar to 1b. Reaction of [4-(trifluoromethyl)phenyl]methanol (4a) provided the thiocarbonate 4b in good yield.  相似文献   

17.
The complexation reaction between uranyl (II) nitrate, and N-methyliminobis(methylenephosphonic acid) (MIDPH) was investigated in two different binary solvent mixtures of D2O-DMSO-d6 at various temperatures using 31P NMR spectroscopy. The exchange between the free ligand and the 1:1 complexed ligand was slow on the NMR timescale and two 31P NMR signals were observed. The formation constant of the resulting complex was evaluated from integration of the two 31P NMR signals. The values of thermodynamic parameters of the resulting complex (ΔH, ΔS and ΔG) were determined from the temperature dependence of the formation constants. In the two solvent mixtures studied, the resulting complex is enthalpy stabilized but entropy destabilized.  相似文献   

18.
Sonogashira cross-coupling reactions involving (E)-iodo vinyl stannanes and terminal acetylenes were carried out in the presence of Pd(PPh3)4, CuI and several amines, affording (Z)-tributylstannyl enynes in moderate to good yields (62-91%). Utilizing the catalytic system containing Pd(PPh3)4 (5%), CuI (10%), and TBAOH (40% in aqueous media) as activator, better yields (72-91%) and lower reaction times were achieved.  相似文献   

19.
Highly crystalline one-dimensional (1D) α-MnO2 nanostructures were synthesized by a hydrothermal method. All samples were characterized by X-ray diffraction, transmission electron microscope, thermogravimetric and differential scanning calorimeter, and infrared spectroscopy. During the formation reactions, the tunnel structure of 1D α-MnO2 was simultaneously modified by NH4+ species and water molecules. The amount of NH4+ species that were trapped in the tunnels is almost independent on the reaction temperature, while the total water content increased with the reaction temperature. The average diameter of α-MnO2 nanorods increased from 9.2 to 16.5 nm when the reaction temperature increased from 140 to 220 °C. 1D α-MnO2 was destabilized by a subsequent high-temperature treatment in air, which is accompanied by a structural transformation to 1D Mn2O3 of a cubic structure. At low temperatures, all 1D α-MnO2 nanorods showed two magnetic transitions that were characterized by a decreased Néel temperature with rod diameter reduction. According to the effective magnetic moments experimentally measured, Mn ions presented in the nanorods were determined to be in a mixed valency of high spin state Mn4+/Mn3+.  相似文献   

20.
In view of industrial importance of binary {ethyl alcohol + (propan-1-ol/propan-2-ol)} mixtures, the densities (ρ) and refractive indices (n D ) of these alkanols mixtures were measured for different compositions at 303.15 K. Molar volumes (V m) and excess molar volumes (V E) of these binary mixtures were calculated from experimental density data of pure solvents and solvents mixtures. The measured refractive index and density data was used to calculate specific refractions (R D ), molar refractions (R M) and apparent molar refractions (R φ, i ) of binary mixtures. From mole fraction dependence of apparent molar refractions, the limiting apparent molar refractions (R φ, i ) of propan-1-ol and propan-2-ol have been determined. The graphical values of R φ, i for propan-1-ol and propan-2-ol were found to be 9.5664 and 7.405 cm3 mol?1 respectively. Structural changes, geometrical fittings and molecular interactions in binary mixtures of these alkanols have been discussed.  相似文献   

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