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1.
Diethyl (1,2-dibromoethyl)phosphonate was found to undergo cyclopropanation with nitromethane in good yield. The resulting trans β-nitrocyclopropylphosphonate was converted to the trans N-protected aminocyclopropylphosphonate through a reduction–protection sequence. Subsequent hydrolysis gave the free β-aminocyclopropylphosphonic acid without any formation of ring-opening byproduct. Cyclopropanation of 1,2-dibromoethylphosphonates with nitroalkanes and their reduction are also discussed. 相似文献
2.
Semenenko A. N. Babak N. L. Gella I. M. Musatov V. I. Shishkina S. V. Sofronov D. S. Lipson V. V. 《Russian Journal of Organic Chemistry》2017,53(2):282-289
Russian Journal of Organic Chemistry - Crotone condensation of allobetulone with fluorine-containing benzaldehydes afforded new α,β-unsaturated ketones of lupane series. Their... 相似文献
3.
The diastereoselectivity of the nucleophilic epoxidation of O-protected 3-hydroxy-1-nitroalkenes was investigated. Epoxidation of the O-protected 3-hydroxy-1-nitroalkenes was highly stereoselective, giving rise to the anti isomer. The resulting nitroepoxides have been transformed into nitroaldols through hydrogenation. The nucleophilic epoxidation of nitroalkenes was found to be irreversible. Models to explain the observed stereoselectivities are proposed. 相似文献
4.
Hani Salim 《Tetrahedron letters》2008,49(18):2994-2995
UV irradiation of ethyl 3-cyclobutylpropen-2-oate delivered the β,γ-unsaturated isomer in high yield. Its CC double bond was submitted to epoxidation and cyclopropanation to deliver the corresponding spiro[3.2]hexane derivatives. Alternatively, the same substrate treated by TMS-I or by OsO4 allowed an easy access to two spiranic butyrolactones. 相似文献
5.
研究了以铜化合物催化重氮乙酸乙酯与烯烃的环丙烷化反应,首次计算了反应关键中间体铜-卡宾的环丙烷化选择性P及该中间体的解离常数K,结果表明:1.反应体系中可能存在着铜-卡宾与游离卡宾的平衡;2.P、K与所用的催化剂有关。使用不同的催化剂,温度对反应选择性的影响也不同,对以上结果进行了理论探讨。 相似文献
6.
Shenquan Guo Niuniu Zhang Xiangzheng Tang Zhifeng Mao Xuejing Zhang Ming Yan Yining Xuan 《中国化学快报》2019,30(2):406-408
An efficient synthesis of β-alkoxycarbonyl vinylsulfonium salts had been developed. Their reaction with indene-1,3-diones and other active methylene compounds provided cyclopropane carboxylates in good yields. A tentative reaction mechanism was proposed. 相似文献
7.
Catalytic Diastereo- and Enantioselective Cyclopropanation of gem-Dihaloalkanes and Terminal Olefins
Hou-Lu Liu Xinyu Wang Ke Gao Zhaobin Wang 《Angewandte Chemie (International ed. in English)》2023,62(28):e202305987
Chiral cyclopropane derivatives are essential in synthetic chemistry and drug discovery. Their synthesis commonly relies on asymmetric cyclopropanation of diazo compounds, potentially explosive and needing stabilizing substituents. Thus, asymmetric catalytic transformations of non-stabilized carbenes or carbenoids remain a formidable challenge. Herein, we report the unprecedented chromium-catalyzed asymmetric cyclopropanation of readily available gem-dihaloalkanes and terminal olefins. Distinct from previous approaches, gem-dihaloalkanes serve as suitable precursors for non-stabilized carbenes or carbenoids, furnishing various functionalized chiral cyclopropanes. Mechanistic studies, including radical trapping, non-linear effect, and UV/Vis spectroscopy, provide insights into the catalytic process, featuring radical-polar crossover. 相似文献
8.
Cyclopropanation reactions of 6-deoxyhex-5-enopyranosides by methylene-zinc-iodide complex, dichlorocarbene, and rhodium ethoxycarbonyl complex addition afford optimum yields of the corresponding spirocyclopropanes. Surprisingly, a stereospecific spirocyclopropane derivative with the two halogens on the upper face of the 4-hydroxy substituent is obtained. To get more insight on the dichlorocarbene cyclopropanation process a computational study, based on DFT quantomechanic calculation was conducted. 相似文献
9.
制备了不同金属改性的钛硅分子筛样品M-TS-1 (M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, La, 负载量为1%), 并研究了其催化丁二烯环氧化反应的性能. 结果表明, V, Cr, Mn的加入导致H2O2无效分解, 因而在丁二烯环氧化反应中表现出较高的H2O2转化率和较低有效利用率; Fe, Co, Ni以及稀土金属La均在一定程度上促进了TS-1对H2O2的有效利用; Cu, Zn抑制了H2O2的转化, 使得H2O2转化率和有效利用率都较低; Cd有效提高了TS-1的催化活性, H2O2转化率和有效利用率均接近100%. 采用X射线衍射、N2吸附-脱附、X射线光电子能谱、傅里叶变换红外光谱等手段表征了上述各金属的改性对TS-1骨架结构以及Ti活性中心周围电子环境的影响. 结果表明, 各M-TS-1样品的骨架结构都仍保持原有的MFI构型, 但是TS-1中Ti活性中心周围的电子环境受到来自各种金属的不同程度影响, 关联催化活性时没有特定的规律性. 相似文献
10.
11.
The synthesis of [Me2N(CH2)2]2Sn(OSit‐Bu2OH)2 ( 1 ) by the base‐assisted cohydrolysis of [Me2N(CH2)2]2SnCl2 and t‐Bu2SiCl2 is described. The molecular structure of 1 , determined by single crystal X‐ray diffraction analysis, features a pentacoordinated tin atom owing to the intramolecular coordination of the nitrogen atom of one 3‐dimethylaminopropyl group, and reveals both intramolecular Si(Sn)O···H‐O and intermolecular N···H‐O hydrogen bonding. Compound 1 is a rare example of a metallasiloxanol and holds potential for the preparation of multi component oxide materials. 相似文献
12.
13.
A mixture of cyclohexanone or 4-methylcyclohexanone and an aromatic aldehyde is treated with dimethylsulfoxonium methylide to effect a tandem aldol/epoxidation reaction. The resulting product contains three or four new stereocenters but only one of the possible four or eight diastereomers is formed. 相似文献
14.
An easy and efficient method for the synthesis of multisubstituted cyclopropane derivatives from electron-deficicent alkenes with 2-bromo-1,3-propanedione compounds was described. For this method, ethyl α-cyanocinnamate derivatives 1 and β,β-dicyanostyrene derivatives 4 can all smoothly react with 2-bromo-1,3-propanedione compounds 2 to afford the corresponding multisubstituted cyclopropane derivatives 3 and 5 in good to excellent yields(up to 100%) promoted by anhydrous K3PO4 in DMF at room temperature, respectively. A possible mechanism of this reaction was proposed. Structures of all the products were confirmed by 1H NMR, 13C NMR and HRMS. 相似文献
15.
A new PS-DVB supported phthalic anhydride and UHP (urea-hydrogen peroxide complex) have been used for metal-free alkene epoxidation reactions. The resin was prepared by MW mediated ‘PEGylation’ of Merrifield resin followed by esterification with trimellitic anhydride chloride. Epoxidation of several alkenes was carried out with this resin and UHP. 相似文献
16.
炔丙型硫Ylide环丙烷化反应及其立体选择性 总被引:1,自引:1,他引:0
炔丙型硫Ylide与丙烯酸酯的反应是一个多反应竞争的复杂反应, 通常环丙烷化产物收率很低. 本文通过对反应底物的优化, 成功获得了高收率、高选择性的反式环丙烷化产物. 同时利用Gaussian 03程序, 选择密度泛函BHHLYP方法, 6-31G**基组对反应路径及过渡态模型进行了计算, 进而采用密度泛函理论中的B3LYP方法, 选择6-31G**基组, 对顺、反式产物的热稳定性进行了分析, 明确了该反应的高非对映选择性是由过渡态的能量差异和产物的热稳定性两个因素共同决定的, 而过渡态的能量差异可以归于分子内弱的立体电子效应的不同. 相似文献
17.
Sandra Lee 《Tetrahedron》2006,62(49):11413-11424
A rare example of a hypervalent iodine reagent participating in a 1,4-heteroconjugate addition reaction is reported for the organocatalytic, asymmetric epoxidation of α,β-unsaturated aldehydes using imidazolidinone catalyst 1. Development of an ‘internal syringe pump’ effect via the slow release of iodosobenzene from an iminoiodinane source provides high levels of reaction efficiency and enantiomeric control in the asymmetric epoxidation of electron-deficient olefins. 15N NMR studies were conducted to elucidate the reaction pathways that lead to catalyst depletion in the presence of prototypical oxidants. These NMR studies also provided the mechanistic foundation for the application of iminoiodinanes as an internal slow release oxidant to circumvent these catalyst depletion pathways. 相似文献
18.
Shingo Ishikawa Reuben Hudson Mitra Masnadi Mary Bateman Annie Castonguay Nadi Braidy Audrey Moores Chao-Jun Li 《Tetrahedron》2014
Simple bare copper-plated iron nanoparticles catalyzed the cyclopropanation of diazoesters with styrene derivatives. The reaction proceeded smoothly and provided the desired products in moderate to good yields, with selectivity for the trans isomer in neat conditions. The reaction scope was explored and di or tri-substituted cyclopropanes were synthesized. The catalysts could be magnetically separated and reusable up to five times. It was also characterized by TEM, XPS, and ICP-MS. A gram-scale reaction was performed with a yield of 72%. 相似文献
19.
R. I. Kureshy N. H. Khan S. H. R. Abdi S. T. Patel P. Iyer 《Journal of molecular catalysis. A, Chemical》1999,150(1-2):163-173
Ruthenium(II) chiral Schiff base complexes 1–10 and their precursor ligands derived from
-amino acids viz.
-leucine,
-histidine with salicylaldehyde, 3-tertiary-butyl-, 3,5-di-tertiary-butyl-, 3,5 dichloro- and 3,5-dinitrosalicylaldehyde are reported. The characterization of the ligands and complexes was accomplished by various appropriate physico-chemical studies, namely, microanalysis, IR-, UV/Vis-, 1H, 31P{1H} NMR, CD spectroscopy, optical rotation, conductance measurement and cyclic voltammetry. The complexes thus synthesised were used as catalysts for enantioselective epoxidation of 1,2-dihydronaphthalene. The effect on enantioselectivity and chemical conversions to epoxide were studied in different solvents viz. acetonitrile, dichloromethane and fluorobenzene along with change of the substituents on ligands and different terminal oxidants. The less polar nature of solvent as well as the donating group attached on the catalysts favours enantioselectivity, while PhIO was the oxidant of choice. The enantiomeric excess of the resulting epoxide was evaluated by chiral cyclodex BDA capillary column. 相似文献
20.
Two molybdenum (VI) hydrogen-bonded network polymers [MoO2F4]·(4,4′-H2bpd)(H2O)2 (1) and [MoO2Cl3(H2O)]·(4,4′-H2bpd)Cl (2) (bpd = bipiperidine) have been synthesized and examined as catalysts for epoxidation of cyclooctene. Complexes of the Mo
compounds containing the bpd ligand are prepared and characterized by infrared spectroscopy, thermogravimetric and elemental
analyses. They have been structurally characterized by single crystal X-ray diffraction analysis. The structures of both the
complexes are shown to be comprised of molybdenum and two protonated N-ligand cations that have resulted in a cross-linked
hydrogen-bonded network structure. These complexes are applicable as catalysts for the cis-cyclooctene epoxidation reactions with hydrogen peroxide as a source of oxygen and NaHCO3 as a cocatalyst. It has been observed that the formation of the oxidant peroxymonocarbonate ion, HCO4
− by hydrogen peroxide and bicarbonate enhances the epoxidation reaction. Both the complexes have exhibited a good activity
and a very high selectivity for the formation of cyclooctene oxide.
An erratum to this article can be found at 相似文献