共查询到20条相似文献,搜索用时 625 毫秒
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先前,我们报道了具有O3BN构架的手性螺硼酸酯催化的前手性酮、肟醚、亚胺的不对称硼烷还原反应[1-3].为了拓宽此类化合物在不对称合成中的应用范围,我们考察了手性螺硼酸酯与格氏试剂的反应.首次发现:具有O3BN构架的手性螺硼酸酯易于发生B-烃基化反应给出三配位的手性烃基硼酸酯,这就为不对称同系化反应、不对称Suzuki偶联反应等奠定了材料基础.四配位的螯合硼酸酯与格氏试剂反应的研究文献中迄今未见报道.在这篇论文中,我们将初步报告手性螺硼酸酯的这一新反应. 相似文献
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《有机化学》2017,(10)
有机硼化合物在合成化学、材料科学、生命健康等领域都有广泛应用,因此有机硼化合物的合成一直是研究热点.目前,催化C—B键形成反应通常使用联硼酸频哪醇酯(B2Pin2)、频哪醇硼烷(HBPin)、儿茶酚硼烷(HBCat)等作为硼试剂.相比于传统的硼试剂,硼烷与胺、膦或N-杂环卡宾等强Lewis碱的加合物(统称为稳定硼烷加合物)具有易于合成、稳定性高、易操作等特点,其作为硼试剂参与的有机硼化合物的合成最近受到越来越多的关注,已被成功用于烯(炔)烃的硼氢化、C—H键硼化、卡宾对B—H键的插入、硼自由基串联环化、取代等反应中,为有机硼化合物的合成提供了新的思路和方法.以反应类型为线索,系统综述了稳定硼烷加合物在有机硼化物合成中的应用研究进展. 相似文献
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Efrn V. García-Bez Itzia I. Padilla-Martínez Feliciano Tamay-Cach Alejandro Cruz 《Molecules (Basel, Switzerland)》2021,26(21)
Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation reactions with carbon dioxide (CO2) are included. Conventional methods with the use of acid and metal catalysts as well as recent green techniques, such as microwave irradiation, the use of ionic liquids, and ultrasound (US) chemistry, which have proven to have many advantages, were found in the review. 相似文献
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Peter W. Roesky 《无机化学与普通化学杂志》2003,629(11):1881-1894
The amido metal chemistry of the rare earth elements is a rapid developing area in coordination chemistry. Especially bulky mono and bidentate amido and amidinates have been introduced as ligands in rare earth chemistry. Due to these sterically demanding ligands, the coordination numbers of the rare earth elements are significantly reduced. This article focuses on two of these bulky ligand systems: bis(trimethylsilyl)amide and aminotroponiminates. The homoleptic bis(trimethylsilyl)amides of rare earth elements, [Ln{N(SiMe3)2}3], are well established compounds in synthetic chemistry. Therefore, this article reviews recent progress in the catalytic application of these compounds. In the second part of this research report, it is shown that N, N′‐disubstituted aminotroponiminates and mono bridged bisaminotroponiminates can be used as cyclopentadienyl alternatives. Achiral and chiral aminotroponiminates have been used. The structural properties, reactivities as well as the catalytic and synthetic applications of the aminotroponiminates complexes will be outlined in this article. 相似文献
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Gerhard Maas Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(44):8186-8195
Diazo compounds (R1R2C?N2) are known as versatile and useful substrates for an array of chemical transformations and, therefore, diazo chemistry is still far from losing anything of its long‐standing fascination. In addition to many studies on the subsequent chemistry of the diazo group, the inventory of methods for the preparation of diazo compounds is continuously supplemented by new methods and novel variations of established procedures. Several of these synthetic approaches take into account the lability and remarkable chemical reactivity of certain classes of diazo compounds, and environmentally more benign procedures also continue to be developed. 相似文献
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Prof. Dr. Kazuaki Ishihara Kazuki Nishimura Katsuya Yamakawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17794-17800
Catalytic enantioselective α-fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α-fluorinated carbonyl compounds. Nevertheless, α-fluorination of α-nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pKa values of their α-hydrogen atoms and difficulty of subsequent synthetic transformation without epimerization. Herein we show that chiral copper(II) complexes of 3-(2-naphthyl)-l -alanine-derived amides are highly effective catalysts for the enantio- and site-selective α-fluorination of N-(α-arylacetyl) and N-(α-alkylacetyl) 3,5-dimethylpyrazoles. The substrate scope of the transformation is very broad (25 examples including a quaternary α-fluorinated α-amino acid derivative). α-Fluorinated products were converted into the corresponding esters, secondary amides, tertiary amides, ketones, and alcohols with almost no epimerization in high yield. 相似文献
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The transfer hydrogenation of bicyclic and monocyclic β-keto esters using HCO2H/Et3N as the hydrogen source and TsDPEN-based Ru(II) catalysts proceeds with dynamic kinetic resolution to afford the corresponding cyclic β-hydroxy esters with moderate to excellent levels of diastereo- and enantioselectivities. The mild reaction conditions used make possible to preserve in most cases the syn relative configuration of the products, providing a complementary tool to known approaches to the synthesis of anti isomers. 相似文献
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Incorporation of the fluoromethyl group can profoundly influence the physicochemical properties of organic molecules, offering a promising strategy for the discovery of novel pharmaceutical agents. Direct fluoromethylation of unfunctionalized C(sp2) centres can be achieved using fluoromethyl radicals, but current methods for their generation usually rely on the activation of non-commercial or expensive radical precursors via inefficient single electron transfer pathways, which limits their synthetic application. Here we report the development of a fluoromethylation strategy based on the generation of fluoromethyl radicals from commercially available fluoroiodomethane via halogen atom transfer. This mode of activation is orchestrated by visible light and tris(trimethylsilyl)silane, which serves as both a hydrogen- and halogen atom transfer reagent to facilitate the formation of C(sp3)–CH2F bonds via a radical chain process. The utility of this metal- and photocatalyst-free transformation is demonstrated through the multicomponent synthesis of complex α-fluoromethyl amines and amino acid derivatives via radical addition to in situ-formed iminium ions, and the construction of β-fluoromethyl esters and amides from electron-deficient alkene acceptors. These complex fluoromethylated products, many of which are inaccessible via previously reported methods, may serve as useful building blocks or fragments in synthetic and medicinal chemistry both in academia and industry.Generation of fluoromethyl radicals via visible light-mediated halogen atom transfer activation of fluoroiodomethane facilitates both the multicomponent synthesis of α-fluoromethyl amines and the hydrofluoromethylation of electron-deficient alkenes. 相似文献
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Dr. Stephan Dohmen Dr. Martin Reiher Dominik Albat Dr. Sema Akyol Dr. Matthias Barone Dr. Jörg-Martin Neudörfl Dr. Ronald Kühne Prof. Dr. Hans-Günther Schmalz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(14):3049-3053
A general and powerful method for the stereo-controlled Pd-catalyzed N-allylation of amino acid esters is reported, as a previously largely unsolved synthetic challenge. Employing a new class of tartaric acid-derived C2-symmetric chiral diphosphane ligands the developed asymmetric amination protocol allows the conversion of various amino acid esters to the N-allylated products with highest levels of enantio- or diastereoselectivity in a fully catalyst-controlled fashion and predictable configuration. Remarkably, the in situ generated catalysts also exhibit outstanding levels of activity (ligand acceleration). The usefulness of the method was demonstrated in the stereo-divergent synthesis of a set of new conformationally defined dipeptide mimetics, which represent new modular building blocks for the development of peptide-inspired bioactive compounds. 相似文献
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The Group IV bent metallocenes Cp2M (M = Ti, Zr, Hf) were involved in carbene-related chemistry in various ways. Examples from four different areas are used to illustrate this. In situ generated Cp2M: species exhibit some carbene-like character. They add to olefins, and their addition products can incorporate additional unsaturated organic reagents, e.g., alkyne, to form five-membered metallacycles. The high oxophilicity of the Group IV metals helps the addition of alkene-, aryne-, 2-ketone-, 2-aldehyde-, or butadiene-containing reagents to a great variety of metal carbonyl compounds to form the Fischer-type carbene complexes. The resulting zirconoxycarbene complexes have found some application in organometallic chemistry and in organic synthesis. Reactive [Cp2MIVR]+ cations can be stabilized by the addition of the Arduengo carbenes that serve as bulky two-electron donor ligands. First examples were structurally characterized. Dialkylimidazol-2-ylidenes also add to the electrophilic MX4 compounds yielding stable trans-bis(imidazol-2-ylidene)MX4 systems. Several examples are presented where ruthenium carbene complexes are used for carrying out catalytic olefin metathesis reactions at pendant olefinic substituents at the bent metallocenes. These reactions have led to the formation of novel bimetallic metallocene systems, as well as to new ansa-metallocenes. These catalytic reactions have helped in the current efforts to develop a functional group chemistry at the sensitive Group IV bent metallocene frameworks. 相似文献
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Dr. Tom Wirtanen Santeri Aikonen Dr. Mikko Muuronen Dr. Michele Melchionna Dr. Marianna Kemell Fatemeh Davodi Prof. Tanja Kallio Dr. Tao Hu Dr. Juho Helaja 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12288-12293
HNO3-oxidized carbon nanotubes catalyze oxidative dehydrogenative (ODH) carbon–carbon bond formation between electron-rich (hetero)aryls with O2 as a terminal oxidant. The recyclable carbocatalytic method provides a convenient and an operationally easy synthetic protocol for accessing various benzofused homodimers, biaryls, triphenylenes, and related benzofused heteroaryls that are highly useful frameworks for material chemistry applications. Carbonyls/quinones are the catalytically active site of the carbocatalyst as indicated by model compounds and titration experiments. Further investigations of the reaction mechanism with a combination of experimental and DFT methods support the competing nature of acid-catalyzed and radical cationic ODHs, and indicate that both mechanisms operate with the current material. 相似文献