共查询到19条相似文献,搜索用时 31 毫秒
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二苯基甲基烯丙基型膦烷与醛的Wittig反应的立体化学研究 总被引:1,自引:0,他引:1
利用3-甲氧基羰基-2-稀丙基二苯基甲基膦叶立德与醛(脂肪醛、芳香醛、杂环醛)的Wittig反应合成了5-取代-2,4-戊二烯酸甲酯(ABA酯类似物),研究了碱对Wittig反应立体化学的影响,发现了该类型季鏻盐的Wittig反应具有很好的4E选择性,并提出了可能的反应机理. 相似文献
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[3,3]σ迁移反应作为有机化学中的经典反应,自发现以来,反应类型不断扩大,且一直广泛应用于有机与药物合成等领域.因为羟胺衍生物的N-O键强度较弱,较易断裂,[3,3]σ迁移反应在较为温和的条件下即可进行,得到含有羟基和氨基的复杂分子,近年来,该类反应引起越来越多的关注.综述了羟胺衍生物的[3,3]σ迁移反应,包括N-... 相似文献
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介绍戊二烯基苯基醚和1,3,7,9-癸四烯衍生物重排反应的机理。戊二烯基苯基醚的重排反应是经过[5,5]和串联的[3,3]σ迁移反应双途径进行的;而1,3,7,9-癸四烯衍生物重排反应既可以经过[5,5]和串联的[3,3]σ迁移反应双途径进行,也可以经过自由基机理进行。 相似文献
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本文对含有手性碳原子的[3,3]σ迁移反应的立体化学过程进行了讨论,重点讨论了含有手性碳原子的Cope重排和Claisen重排的产物及其生成的立体化学过程。 相似文献
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Prof. Dr. Hideki Yorimitsu 《Chemical record (New York, N.Y.)》2017,17(11):1156-1167
A new class of Pummerer chemistry has emerged as a powerful tool in organic synthesis. The new technology consists of a beautiful cascade of an interrupted Pummerer reaction and the subsequent [3,3] sigmatropic rearrangement. The interrupted Pummerer reactions of alkenyl or aryl sulfoxides with unsaturated nucleophiles such as allylic silanes, ketones, and phenols provide sulfonium intermediates, which are ready to undergo smooth charge‐accelerated [3,3] sigmatropic rearrangement with excellent to exclusive regioselectivity. Some of the transformations proceed with transient loss of aromaticity. The reactions afforded five‐membered heterocycles, benzofurans, and biaryls of importance, depending on the sulfoxides and nucleophiles used. The reactions are unique and game‐changing because they are efficient, robust, redox‐neutral, regioselective, and metal‐free, which perfectly fits the need of modern organic synthesis. This chemistry also underscores the synthetic potential of organosulfur chemistry. 相似文献
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Itiswellknownthattheallylc0mP0undsexhibitavariety0finterestingrearrangementreacti0ns.Intheliquidphase,temPerature-inducedClaisenrearrangement,cyclizationreactionsandacid-induced0rthoClaisenrearrangementsofallylphenyletherhavebeenstUdiedextensively.'-'However,theClaisenrearrangementinthegasphasewasrepoftedonlyrecelltly,includingtheprotonatedallylphenyletherandN-allylanilineunderpositivecheITilcalionizationcondition4",thedeprotonatedallylphenylacetateanddeprotonatedallylphenyletherundernegati… 相似文献
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Tomoyuki Yanagi Dr. Keisuke Nogi Prof. Dr. Hideki Yorimitsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):783-787
An unprecedented S−N variant of the benzidine rearrangement for construction of biaryls has been developed. Aryl sulfoxides underwent dehydrogenative coupling with anilines by successive treatment with trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid to provide the corresponding 2-amino-2′-sulfanyl- and/or 4-amino-4′-sulfanylbiphenyls. Mechanistic studies indicate that the C−C-bond-forming sigmatropic rearrangement proceeds intramolecularly from dicationic S−N-tethered species. 相似文献
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Dr. Tomoyuki Yanagi Prof. Dr. Hideki Yorimitsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(53):13450-13456
A comprehensive mechanistic investigation was conducted on the coupling reaction of aryl sulfoxides with phenols by using trifluoroacetic anhydride to yield biaryls. NMR experiments revealed that our previously proposed mechanism, which consists of a cascade of an interrupted Pummerer reaction and a rate-determining [3,3] sigmatropic rearrangement, is reasonable. The electronic effects of the substrates were also evaluated to elucidate the nature of the rearrangement step. Based on experimental observations and theoretical calculations, we conclude that the rearrangement is highly asynchronous and stepwise rather than concerted when electron-rich phenols are employed for the reaction. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(36):10938-10941
The use of readily available hydroxamic acids as reagents for the chemoselective (ortho‐amino)arylation of amides is described. This reaction proceeds under metal‐free, mild conditions, displays a very broad scope, and constitutes a direct approach for the metal‐free attachment of aniline residues to carbonyl derivatives. 相似文献
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Masato Ichiki Dr. Hiroki Tanimoto Shohei Miwa Ryosuke Saito Dr. Takaaki Sato Prof. Noritaka Chida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(1):264-269
A detailed exploration of the synthesis of (?)‐morphine based on sequential [3,3]‐sigmatropic rearrangements is described. The sequential Claisen/Claisen rearrangements of an allylic vicinal diol resulted in the stereoselective formation of the two contiguous carbon centers, including a sterically encumbered quaternary carbon, in a single operation. The two ethyl esters generated in this reaction were successfully differentiated during a subsequent Friedel–Crafts‐type cyclization. The (?)‐morphine double bond was introduced at a late stage in our first‐generation synthesis, but was formed at an earlier stage in the second‐generation synthesis, resulting in a more efficient route to the end product. 相似文献
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Selective ortho C−H Cyanoalkylation of (Diacetoxyiodo)arenes through [3,3]‐Sigmatropic Rearrangement 下载免费PDF全文
Junsong Tian Fan Luo Chaoshen Zhang Xin Huang Yage Zhang Lei Zhang Lichun Kong Xiaochun Hu Prof. Zhi‐Xiang Wang Prof. Dr. Bo Peng 《Angewandte Chemie (International ed. in English)》2018,57(29):9078-9082
We herein report a robust catalyst‐free cross‐coupling between ArI(OAc)2 and α‐stannyl nitriles, aided by TMSOTf. The transformation introduces a cyanoalkyl group to the ortho position of ArI(OAc)2 and simultaneously reduces the aryl iodine(III) to iodide, thus providing α‐(2‐iodoaryl) nitrile as the product. This transformation could be completed within 5 min at ?78 °C and features superb functional‐group tolerance and efficient scalability. DFT calculations indicate that the formation of a ketenimine(aryl)iodonium intermediate and subsequent [3,3]‐sigmatropic rearrangement are involved as key steps. 相似文献