共查询到20条相似文献,搜索用时 31 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):11040-11044
Re2O7 catalysis effects efficient and stereoselective dehydrative cyclization reactions from monoallylic diols, with stereocontrol arising from thermodynamic equilibration. This method was applied to a rapid synthesis of the spliceosome inhibitor herboxidiene. The route was also utilized for the synthesis of an analogue that highlights the importance of a single methyl group in biasing the conformation in the acyclic region of the molecule. 相似文献
2.
Shukun Li 《Tetrahedron》2005,61(47):11291-11298
A seco-precursor of macrolactin A was synthesized by coupling two advanced segments. Wittig reaction and Horner-Emmons reaction were utilized to construct the three characteristic E,Z and E,E dienes. The C1-C10 segment was synthesized through Horner-Emmons reaction with phosphonate reagent. The α-alkylation of sulfone stabilized anion with allyl bromide followed by desulfonation gave the C11-C24 segment. 相似文献
3.
The Ph3PAuCl/AgOTf-catalyzed cyclization of monoallylic diols to form tetrahydropyrans is reported. The reactions proceed rapidly at temperatures as low as -78 degrees C with catalyst loadings as low as 0.1 mol % to provide the products in 79-99% yield. A broad range of structurally diverse substrates perform well in the reaction. When 2,6-disubstituted tetrahydropyrans are produced, the reaction is highly diastereoselective for the 2,6-cis product. 相似文献
4.
Alkynyl cyanides are found to add across alkynes and 1,2-dienes in the presence of a catalyst prepared in situ from Ni(cod)2, xantphos, and BPh3. A range of functionalized conjugated cis-enynes are obtained with high regioselectivity. The addition reaction across norbornadiene proceeds in the absence of BPh3 to give exo-cis adduct exclusively. A stoichiometric reaction of an alkynyl cyanide, Ni(cod)2, xantphos, and BPh3 gives trans-(xantphos)Ni(CNBPh3)(CCSiMe2t-Bu), which is suggested to be a plausible reaction intermediate of the alkynylcyanation reaction. 相似文献
5.
V. A. Aver’yanov S. A. Batashev N. T. Sevost’yanova N. M. Nosova 《Kinetics and Catalysis》2006,47(3):375-383
The kinetics of cyclohexene hydrocarbomethoxylation catalyzed by the Pd(PPh3)2Cl2-PPh3-p-toluenesulfonic acid (TSA) is reported. The reaction is first-order with respect to cyclohexene and TSA and of order 0.5 with respect to Pd(PPh3)2Cl2. The reaction rate as a function of CO pressure or methanol or PPh3 concentration passes through an extremum. The chloride anion inhibits the reaction. A mechanism involving cationic hydride complexes as intermediates is suggested. A rate equation is set up by the quasi-steady-state treatment of experimental data. 相似文献
6.
A theoretical investigation of the reaction mechanism and kinetics of the reaction between chloromethanes CH4–xClx (x = 1–3) and chlorine atoms was performed. The height of the reaction barrier was found to decrease with the degree of substitution of chloromethanes with atomic chlorine. A direct dynamics method was employed to study the kinetic nature of these hydrogen-abstraction reactions. The sequence of calculated reaction rate coefficients is: k(CH3Cl + Cl) < k(CH2Cl2 + Cl) < k(CHCl3 + Cl). 相似文献
7.
《Chemical physics letters》1985,118(5):530-533
The energy distribution of nascent OH(2Π, υ, J) produced in the reaction of O(1D) with H2S has been measured by laser-induced fluorescence. The rotational distributions in υ″ = 0 and υ″ = 1 are Boltzmannian with temperature parameters Tr″-0 = 2300 ± 100 K and Tr−-1 = 2650 ± 150 K. A population ratio N(υ″ = 1)/N(υ″ = 0) = 0.17 is observed. The product-state distribution over the different spin and A components is statistically within the experimental uncertainty of 20%. A comparison of the OH product populations from the title reaction with the well known OH yield from the O(1D)+H2O reaction shows that 25% of the reactive encounters follow the reaction channel which produces OH in υ″ = 0 and υ″ = 1. 相似文献
8.
Mitsutaka Iwata Ryo Yazaki Naoya Kumagai Masakatsu Shibasaki 《Tetrahedron: Asymmetry》2010,21(13-14):1688-1694
A direct catalytic asymmetric aldol reaction of aromatic aldehydes and thioamides is described. A soft Lewis acid/hard Brønsted base cooperative catalyst comprising (R,R)-Ph-BPE/[Cu(CH3CN)4]PF6/Li(OC6H4-p-OMe) promoted the title reaction efficiently, triggered by in situ generation of the active thioamide enolate through a soft–soft interaction of Cu(I) and the thioamide. The aldol product was transformed into (R)-fluoxetine, an antidepressant agent. 相似文献
9.
The reaction of O2(1Δg) with HO2(X?) was studied in an isothermal flow reactor in the pressure range 7?p? 10.7 mbar at temperatures between 299?T? 423 K. H-atom production was observed in the reaction O2(1Δg) + HO2(Ã2A′) - H(2S)+ 2O2 (3Σg?). The rate of this reaction (k1) is estimated to be k1 = (1 ± 0.5) × 1014 CM3 Mol?1 s?1. The implications of this reaction to recent determinations of the rate of the reaction H + O2(1Δg) are discussed. 相似文献
10.
Richard I. Martinez 《Chemical physics letters》1983,98(5):507-510
Observations in the O3 + trans-2-butene reaction system and in the O + trans-2-butene + O2 reaction system suggest the intermediacy of alkenoxy radicals. A mechanism is proposed for the production of Cn and Cm (m <n) alkenoxy radicals by the reaction of CnH2n alkenes with oxygen atoms or with ozone. 相似文献
11.
Takashi Harayama Akihiro Hori Georgeta Serban Yoshiaki Morikami Takuya Matsumoto Hitoshi Abe Yasuo Takeuchi 《Tetrahedron》2004,60(47):10645-10649
The total synthesis of luotonin A was achieved in excellent yield by using a Pd-assisted biaryl coupling reaction of N-(bromoquinolinyl)methylquinazolinone with Cy3P and KOAc. The successive treatment of luotonin A with NBS and aq. AgNO3 gave luotonin B in good yield. Although the Pd-assisted coupling reaction of N-(2-bromoindolyl)ethylquinazolinone with Cy3P and KOAc yielded rutaecarpine in poor yield, N-acetate under the same reaction conditions yielded the desired rutaecarpine directly in excellent yield. 相似文献
12.
Faiz Ahmed Khan Rashmirekha Satapathy Ch. Sudheer Ch. Nageswara Rao 《Tetrahedron letters》2005,46(42):7193-7196
A new reaction of diazomethane with norbornyl α-diketones in MeOH as solvent leading regioselectively to ketals is described. The mechanistic details of this intriguing reaction were investigated employing d4-MeOH, EtOH and d6-EtOH. The surprising observation of complete deuterium incorporation in the diazomethane-derived methoxy group was accounted for by sequential deuterium exchange between the initially formed hemiketal d4-18 and diazomethane in the presence of d4-MeOH as solvent. 相似文献
13.
Masato HigashinoNaoko Ikeda Tetsuro ShinadaKazuhiko Sakaguchi Yasufumi Ohfune 《Tetrahedron letters》2011,52(3):422-425
A novel silyl group-directed anti-SN2′ reaction of allylic alcohols under Mitsunobu reaction conditions is described. The Mitsunobu reaction of α-hydroxy-α-alkenylsilanes with a TBS or TIPS group gave the anti-SN2′ product, in which regio- and stereochemical outcomes of the reaction depended on the steric bulkiness of the silyl group. 相似文献
14.
Poly(?-caprolactone-co-1,2-butylene carbonate) (PBCCL) was successfully synthesized via terpolymerization of carbon dioxide, 1,2-butylene oxide(BO) and ?-caprolactone (CL). A polymer-supported bimetallic complex (PBM) was used as catalyst. The influences of various reaction conditions such as reaction content, reaction time and reaction temperature on properties of terpolymers were investigated. When CL content increased, the viscosity-average molecular weights (Mv), glass transition temperature (Tg) and decomposition temperature (Td) of PBCCL improved relative to those of poly(1,2-butylene carbonate) (PBC). Prolonging the reaction time resulted in increase in Mv and Tg. As reaction temperature increased, the molar fractions of CL (fCL) increased obviously. When the reaction temperature went beyond 80 °C, the resulting copolymers tended to be crystalline. The thermal properties and degradation behaviors of PBCCL were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The apparent activation energy and thermal degradation model of PBCCL was estimated by means of Ozawa-Flynn-Wall method and Phadnis-Deshpande method, respectively. The results showed that Tg and Td of the terpolymer PBCCL were much higher than those of PBC. The thermal degradation behavior of PBCCL was evidenced by one-step thermal degradation profile. The average apparent activation energy is 77.06 kJ/mol, the thermal degradation kinetics follows the power law thermal decomposition model. 相似文献
15.
Deepak Singh Rathore Vimlesh Kumar Meena Chandra Pal Singh Chandel Krishna Swarup Gupta 《印度化学会志》2022,99(9):100631
The trace atmospheric volatile organic compounds(VOCs) are reported to influence the oxidation of dissolved sulfur dioxide, S(IV), by oxygen, which is an important reaction in atmospheric acid formation. In this work, the influence of 15 VOCs on uncatalyzed oxidation of S(IV) by oxygen has been investigated by following the disappearance of [O2]. The inhibition of oxidation reaction by toluene, aniline, benzene, cinnamic acid, hydroquinone, acrylamide, acrylonitrile and allyl alcohol was defined by the rate law(A):kVOC = k0/(1+B [Inh]) (A)where, kVOC, and k0 are the first order rate constants in the presence and the absence of VOCs respectively. B is the inhibition parameter and [Inh] is the concentration of inhibitor.On the other hand, fumaric, maleic and crotonic acids, which have conjugated CC bonds, catalyze the reaction defined by the rate law(B):kVOC = k0 + kcat [VOC] (B)where kcat is catalytic constant and [VOC] is the concentration of catalytic VOC.Interestingly, presence of 1-hexene, cyclohexene, methacrylic acid, methyl acrylate was without any significant effect on the rate of reaction. 相似文献
16.
The kinetics of the oxidation of thiosulphate ions by octacyanotungstate(V) ions has been studied in the pH range 3.9–5.0. The reaction showed zero-order kinetics with respect to [W(CN)83?] and is consistent with the rate law R = k[H+][S2O32?]2. A reaction mechanism is proposed for the reaction with a third-order rate constant of 0.26 M?2 s?1 at 25°C. 相似文献
17.
Mahboubeh RostamiAhmad R. Khosropour Valiollah MirkhaniMajid Moghadam Shahram TangestaninejadIraj Mohammadpoor-Baltork 《Tetrahedron letters》2011,52(52):7149-7152
A rapid and simple procedure for the synthesis of the indenone derivatives, N-(1-oxo-1H-inden-2-yl)benzamides, via intramolecular Friedel-Crafts (IFC) reaction of (Z)-4-arylidene-2-phenyl-5(4)-oxazolones (azlactones) catalyzed by H3PW12O40 supported on neutral alumina under microwave irradiation has been developed. The reaction is straightforward and allows easy isolation of the product. The catalyst could be re-used up to four times after simple filtration. 相似文献
18.
A direct catalytic asymmetric Mannich-type reaction of isomerizable aliphatic imines is described. A Et2Zn/(S,S)-linked-BINOL complex was suitable for chemoselective enolate formation from a hydroxyketone in the presence of isomerizable aliphatic N-diphenylphosphinoyl imines. The reaction proceeds smoothly and β-alkyl-β-amino-α-hydroxyketones were obtained in good yield and high enantioselectivity (up to 99% ee), albeit in modest to low diastereoselectivity. 相似文献
19.
A properly modified inner boundary condition is used in an analysis of the conditional reaction probability, φ*R (r0, t), using the Debye-Smoluchowski equation. It is shown that the Coulomb potential modifies the reaction velocity at the boundary by the addition of a drift term. φ*R (r0, t) is identifical for attractive and repulsive cases if a constant term is added to the boundary velocity for the attractive potential. 相似文献
20.
《Chemical physics》1986,104(2):213-227
A sliding mass model for three-center reactions is formulated which proves to be useful to rationalize the dependence of integral reaction cross section (σr) on reagent rotation (j) by topographic attributes of the potential energy surface (PES). The model allows a clear definition of frequently used terms like “cone of acceptance” and “disruption of the favoured orientation” by rotation. A computational study of reaction probabilities uncovers intimate relations between steric properties of reagent interaction and the shape of σr(j). The oscillatory structure of σr(j) predicted by NoorBatcha and Sathyamurthy for the reaction Li + HF → LiF + H is shown to be due to the ill asymptotic behaviour of the used PES (Carter and Murrell's best fit function to the ab initio of Chen and Schaefer). 相似文献