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41.
Zhao Li Xu Wang Yu-Ming Cui Jun-Han Ma Li-Lei Fang Lu-Lu Han Qin Yang Dr. Zheng Xu Prof. Dr. Li-Wen Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(13):4336-4340
Although asymmetric C−H functionalization has been available for the synthesis of structurally diverse molecules, catalytic dynamic kinetic resolution (DKR) approaches to change racemic stereogenic axes remain synthetic challenges in this field. Here, a concise palladium-catalyzed DKR was combined with C−H functionalization involving olefination and alkynylation for the highly efficient synthesis of non-biaryl-atropisomer-type (NBA) axially chiral oragnosilanes. The chemistry proceeded through two different and distinct DKR: first, an atroposelective C−H olefination or alkynylation produced axially chiral vinylsilanes or alkynylsilanes as a new family of non-biaryl atropisomers (NBA), and second, the extension of this DKR strategy to twofold o,o′-C−H functionalization led to the multifunctional axially chiral organosilicon compounds with up to >99 % ee. 相似文献
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43.
Scott E. Denmark Prof. Dr. Jack H.‐C. Liu Dr. 《Angewandte Chemie (International ed. in English)》2010,49(17):2978-2986
Unlike other variants of transition‐metal‐catalyzed cross‐coupling reactions, those based on organosilicon donors have not been used extensively in natural product synthesis. However, recent advances such as: 1) the development of mild reaction conditions, 2) the expansion of substrate scope, 3) the development of methods to stereoselectively and efficiently introduce the silicon‐containing moiety, 4) the development of a large number of sequential processes, and 5) the advent of bifunctional bis(silyl) linchpin reagents, signify the coming of age of silicon‐based cross‐coupling reactions. The following case studies illustrate how silicon‐based cross‐coupling reactions play a strategic role in constructing carbon–carbon bonds in selected target molecules. 相似文献
44.
This paper chronicles the conceptual development, proof of principle experiments, and recent advances in the palladium-catalyzed cross-coupling reactions of the conjugate bases of organosilanols. The discovery that led to the design and refinement of this process represents a classical illustration of how mechanistic studies can provide a fertile ground for the invention of new reactions. On the basis of a working hypothesis (which ultimately proved to be incorrect) and the desire to effect silicon-based cross-coupling without the agency of fluoride activation, a mild and practical palladium-catalyzed cross-coupling of alkenyl-, aryl-, and heteroaryl silanolates has been developed. The mechanistic underpinnings, methodological extensions, and the successful applications of this technology to the synthesis of complex molecules are described. 相似文献
45.
水/有机溶剂双相中郁李醇腈酶催化含硅(R)-酮氰醇对映选择性合成 总被引:1,自引:0,他引:1
研究了水/有机溶剂双相中来源于郁李仁的(R)-醇腈酶催化2-三甲基硅-2-乙酮与2-甲基-2-羟基丙腈对映选择性合成(R)-2-三甲基硅-2-羟基丙腈,初步探讨了反应时间、酶粉颗粒大小、底物浓度、底物配比和酶添加量对转氰反应的影响. 结果表明,适宜的反应条件为: 反应时间96 h左右, 酶粉颗粒大小0.3~0.45 mm, 底物2-三甲基硅-2-乙酮浓度14 mmol/L, 底物2-甲基-2-羟基丙腈与2-三甲基硅-2-乙酮摩尔比2:1, 单位体积反应介质中的酶添加量43.5 g/L左右. 在该优化反应条件下,反应平衡转化率和产物的光学纯度(ee值)均可高达99%. 对比研究发现,郁李醇腈酶催化2-三甲基硅-2-乙酮反应在酶促反应初速率、底物转化率和产物光学纯度等方面均显著优于其碳结构类似物3,3-二甲基-2-丁酮. 相似文献
46.
具有生物活性的有机硅化合物研究近况 总被引:7,自引:0,他引:7
生物有机硅化合物的研究进展迅速,而且越来越受到人们的重视。实际上,它是有机硅化学的一个新的分支。本文对有机硅化合物的毒理学、有机硅药物化学以及有机硅农药作了简要的论述。 相似文献
47.
γ-氨丙基三乙氧基硅烷与丙烯腈加成,得到γ-(β-氰乙基)胺丙基三乙氧基硅烷。后者依次与气相法二氧化硅、三氯化铑作用,合成了聚γ-(β-氰乙基)胺丙基硅氧烷铑配合物。它对烯烃与三乙氧基硅烷的硅氢加成反应具有良好的催化活性。 相似文献
48.
Borisova I. V. Zemlyanskii N. N. Khrustalev V. N. Nechaev M. S. Kuznetsova M. G. Ustynyuk Yu. A. 《Russian Chemical Bulletin》2002,51(4):678-683
The reactions of ylides R1
3As=CHR2 with hexamethyl-2,4,6-trisila- and hexamethyl-2,4,6-trigermatrithiacyclohexanes afforded betaines R1
3As+—CHR2—SiMe2—S– (2) (R1 = Et; R2 = Ph (a), Me3Si (b); R1 = R2 = Ph (c)) and Et3As+—CH(SiMe3)—GeMe2—S– (3), respectively. Betaines 2a,b and 3 were characterized by multinuclear NMR spectroscopy. According to the X-ray diffraction data, in the crystals the As+—C—E—S– main chain (E = Si or Ge) of molecules 2a,b and 3 adopts a twisted cis conformation due to strong intramolecular Coulomb interactions between the anionic and cationic centers. The equilibrium geometries of isolated molecules 2a and 3, which were calculated within the framework of the density functional theory (the PBE functional, the TZ2P basis set), are in qualitative agreement with the X-ray data. In solutions, betaines 2a (in the absence of Li salts) and 2c (in the presence of LiBr) selectively decomposed according to the Corey—Chaykovsky reaction, which was accompanied by elimination of R3As and, probably, the intermediate formation of silathiirane. The subsequent transformation of the latter afforded 2,2,4,4-tetramethyl-5-phenyl-2,4-disila-1,3-dithiolane. 相似文献
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50.
ZHONG Gui yun LIU Hua XIE Qing lan * Institute of Elemento organic Chemistry Nankai University Tianjin P. R. China 《高等学校化学研究》2002,18(3):277-279
IntroductionThe drug- molecules are called as silyl- drug ifasilicon atom replaced one carbon atom of theorganic- drugs.Generally,they have low toxicityand pro- long efficiency.Many methods have beendesigned in order to decrease the toxicity oforganotin compounds and organosilicon which hasbeen proved to be effective.Torque[1] is a newacaricide made by America Shell Company,itsmolecular formula is [( Ph Me2 Si CH2 ) 3 Sn]2 O.Tacker[2 ] synthesized the compounds( Ph Me2 Si CH2 ) 3 Sn X[… 相似文献