共查询到20条相似文献,搜索用时 15 毫秒
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Marco Colella Arianna Tota Yusuke Takahashi Ryosuke Higuma Susumu Ishikawa Leonardo Degennaro Renzo Luisi Aiichiro Nagaki 《Angewandte Chemie (International ed. in English)》2020,59(27):10924-10928
The external quenching method based on flow microreactors allows the generation and use of short‐lived fluoro‐substituted methyllithium reagents, such as fluoromethyllithium, fluoroiodomethyllithium, and fluoroiodostannylmethyllithium. Highly chemoselective reactions have been developed, opening new opportunities in the synthesis of fluorinated molecules using fluorinated organometallics. 相似文献
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The Donor‐Base‐Free Aggregation of Lithium Diisopropyl Amide in Hydrocarbons Revealed by a DOSY Method 下载免费PDF全文
M.Sc. Roman Neufeld Dr. Michael John Prof.Dr. Dietmar Stalke 《Angewandte Chemie (International ed. in English)》2015,54(24):6994-6998
Lithium diisopropyl amide (LDA) is a very prominent reagent that plays a key role in organic synthesis, serving as a base par excellence for a broad range of deprotonation reactions. However, the state of aggregation in solution in the absence of donor bases was unclear. In this paper we solved this problem by employing DOSY NMR experiments based on a newly elaborated external calibration curve (ECC) approach with normalized diffusion coefficients. 相似文献
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Niteen B. Patil Ranjit S. Atapalkar Dr. Subhash P. Chavan Dr. Amol A. Kulkarni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17695-17699
Herein we report for the first time, an advanced continuous flow synthesis of the blockbuster Leishmaniasis drug miltefosine from simple starting materials by a sequence involving four steps of chemical transformation including a continuous mechanochemical step. First three reaction steps were performed in simple tubular reactors in a telescopic mode, while in the last step the product precipitated from the 3rd step was used for a continuous mechanochemical synthesis of miltefosine. When compared to a typical batch protocol that takes 15 h, miltefosine was obtained in 58 % overall yield in flow synthesis mode at the laboratory scale in a total residence time 34 min at synthesis rate of 10 g/hr, which is sufficient to treat 4800 patients per day. 相似文献
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Dr. Heejin Kim Keita Inoue Prof. Dr. Jun-ichi Yoshida 《Angewandte Chemie (International ed. in English)》2017,56(27):7863-7866
A series of anionic Fries-type rearrangements of carbamoyl-substituted aryllithium intermediates were controlled by using flow microreactor systems. For the [1,4] and [1,5] rearrangements, the aryllithium intermediate formed before carbamoyl migration and the lithium alkoxide formed after carbamoyl migration can be selectively subjected to subsequent reactions with electrophiles by precisely controlling the residence time and temperature (−25 to −50 °C). In contrast, the [1,6] rearrangement is rather slow even at −25 °C. The absence of crossover products indicates the intramolecular nature of the carbamoyl group migration. 相似文献
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Dr. Yosuke Ashikari Dr. Kodai Saito Prof. Dr. Toshiki Nokami Prof. Dr. Jun-ichi Yoshida Prof. Dr. Aiichiro Nagaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(67):15239-15243
The present study describes the cationic oxo-thiolation of polymerizable alkenes by using highly reactive cationic species generated by anodic oxidation. These highly reactive cations were able to activate alkenes before their polymerization. Fast mixing in flow microreactors effectively controlled chemoselectivity, enabling higher reaction temperatures. 相似文献
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Dr. Brijesh M. Sharma Dr. Arun V. Nikam Dr. Santosh Lahore Gwang-Noh Ahn Prof. Dr. Dong-Pyo Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202103777
This work reports a cyanide-free continuous-flow process for cyanation of sp2 and sp carbons to synthesize aryl, vinyl and acetylenic nitriles from (5-methyl-2-phenyloxazol-4-yl) boronic acid [OxBA] reagent as a sole source of carbon-bound masked −CN source. Non-toxic and stable OxBA reagent is generated by lithiation-borylation of bromo-oxazole, and the consecutive Suzuki-Miyaura cross-coupling with aryl, vinyl, or acetylenic halides and demasking [4+2]/retro-[4+2] sequence were successfully accomplished to give the desired cyano compounds with reasonably good yields in a four-step flow manner. A unique feature of this cyanation protocol in flow enables to cyanate a variety of sp2 and sp carbons to produce a broad spectrum of aryl acetonitrile. It is envisaged that the OxBA based cyanation would replace existing unstable and toxic approaches as well as non-toxic cyanation using two different sources of “C” and “N” to incorporate the −CN group. 相似文献
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Jeff Y. F. Wong Dr. John M. Tobin Dr. Filipe Vilela Dr. Graeme Barker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12439-12445
1,3,4-Oxadiazoles are a common motif in pharmaceutical chemistry, but few convenient methods for their modification exist. A fast, convenient, high yielding and general α-substitution of 1,3,4-oxadiazoles has been developed using a metalation-electrophilic trapping protocol both in batch and under continuous flow conditions in contradiction to previous reports which suggest that α-metalation of this ring system results in ring fragmentation. In batch, lithiation is accomplished at an industrially convenient temperature, −30 °C, with subsequent trapping giving isolated yields of up to 91 %. Under continuous flow conditions, metalation is carried out at room temperature, and subsequent in flow electrophilic trapping gave up to quantitative isolated yields. Notably, lithiation in batch at room temperature results only in ring fragmentation and we propose that the superior mixing in flow allows interception and exploitation of an unstable intermediate before decomposition can occur. 相似文献
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Dr. Simon T. R. Müller Tobias Hokamp Svenja Ehrmann Dr. Paul Hellier Prof. Dr. Thomas Wirth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):11940-11942
Ethyl diazoacetate (EDA) is one of the most prominent diazo reagents. It is frequently used in metal–carbene‐type reactions. However, EDA can also be used as a nucleophile under base catalysis. Whilst the addition of EDA to aldehydes can be performed using organic bases, the addition of EDA to other carbonyl electrophiles requires the use of organometallics such as lithium diisopropylamide (LDA). The generated ethyl lithiodiazoacetate is highly reactive and decomposes rapidly, even at low temperatures. Herein, we report a continuous flow protocol that overcomes the problems associated with the instantaneous decomposition of ethyl lithiodiazoacetate. The addition of ethyl lithiodiazoacetate to ketones provides direct access to tertiary diazoalcohols in good yields. 相似文献
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Dr. Nathalie Daro Tony Vaudel Luc Afindouli Dr. Samuel Marre Dr. Cyril Aymonier Dr. Guillaume Chastanet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(69):16286-16290
Switchable materials are increasingly considered for implementation in devices or multifunctional composites leading to a strong need in terms of reliable synthetic productions of well-defined objects. Here, an innovative and robust template-free continuous process was developed to synthesize nanoparticles of a switchable coordination polymer, including the use of supercritical CO2, aiming at both quenching the particle growth and drying the powder. This all-in-one process offers a 12-fold size reduction in a few minutes while maintaining the switching properties of the selected spin crossover coordination polymer. 相似文献
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Extremely Fast Gas/Liquid Reactions in Flow Microreactors: Carboxylation of Short‐Lived Organolithiums 下载免费PDF全文
Dr. Aiichiro Nagaki Yusuke Takahashi Prof. Jun‐ichi Yoshida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):7931-7934
Carboxylation of short‐lived organolithiums bearing electrophilic functional groups such as nitro, cyano, and alkoxycarbonyl groups with CO2 to give carboxylic acids and active esters was accomplished in a flow microreactor system. The successful reactions indicate that gas/liquid mass transfer and the subsequent chemical reaction with CO2 are extremely fast. 相似文献
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Joshua Britton Dr. Justin M. Chalker Prof. Dr. Colin L. Raston 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10660-10665
Thin film flow chemistry using a vortex fluidic device (VFD) is effective in the scalable acylation of amines under shear, with the yields of the amides dramatically enhanced relative to traditional batch techniques. The optimized monophasic flow conditions are effective in ≤80 seconds at room temperature, enabling access to structurally diverse amides, functionalized amino acids and substituted ureas on multigram scales. Amide synthesis under flow was also extended to a total synthesis of local anesthetic lidocaine, with sequential reactions carried out in two serially linked VFD units. The synthesis could also be executed in a single VFD, in which the tandem reactions involve reagent delivery at different positions along the rapidly rotating tube with in situ solvent replacement, as a molecular assembly line process. This further highlights the versatility of the VFD in organic synthesis, as does the finding of a remarkably efficient debenzylation of p‐methoxybenzyl amines. 相似文献
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Dr. Yosuke Ashikari Dr. Takashi Tamaki Tomoko Kawaguchi Mai Furusawa Yuya Yonekura Susumu Ishikawa Dr. Yusuke Takahashi Yoko Aizawa Prof. Dr. Aiichiro Nagaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16107-16111
A chemoselectivity switchable microflow reaction was developed to generate reactive and unstable intermediates. The switchable chemoselectivity of this reaction enables a selection for one of two different intermediates, an aryllithium or a benzyl lithium, at will from the same starting material. Starting from bromo-substituted styrenes, the aryllithium intermediates were converted to the substituted styrenes, whereas the benzyl lithium intermediates were engaged in an anionic polymerization. These chemoselectivity-switchable reactions can be integrated to produce polymers that cannot be formed during typical polymerization reactions. 相似文献
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Rico Warias Dr. Daniele Ragno Prof. Alessandro Massi Prof. Detlev Belder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(58):13152-13156
A versatile one-step photopolymerization approach for the immobilization of enantioselective organocatalysts is presented. Chiral organocatalyst-containing monoliths based on polystyrene divinylbenzene copolymer were generated inside channels of microfluidic chips. Exemplary performance tests were performed for the monolithic Hayashi–Jørgensen catalyst in continuous flow, which showed good results for the Michael addition of aldehydes to nitroalkenes in terms of stereoselectivity and catalyst stability with minimal consumption of reagents and solvents. 相似文献
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Marco Colella Prof. Dr. Aichiiro Nagaki Prof. Dr. Renzo Luisi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(1):19-32
In the field of organic synthesis, the advent of flow chemistry and flow microreactor technology represented a tremendous novelty in the way of thinking and performing chemical reactions, opening the doors to poorly explored or even impossible transformations using batch methods. In this Concept article, we would like to highlight the impact of flow chemistry for exploiting highly reactive organometallic reagents, and how, alongside the well-known advantages concerning safety, scalability, and productivity, flow chemistry makes possible processes that are impossible to control by using the traditional batch approach. 相似文献
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Dr. Jason D. Williams Prof. Dr. William J. Kerr Dr. Stuart G. Leach Dr. David M. Lindsay 《Angewandte Chemie (International ed. in English)》2018,57(37):12126-12130
The addition of carbon nucleophiles to isocyanates represents a conceptually flexible and efficient approach to the preparation of amides. This general synthetic strategy has, however, been relatively underutilized owing to narrow substrate tolerance and the requirement for less favourable reaction conditions. Herein, we disclose a high‐yielding, mass‐efficient, and scalable method with appreciable functional group tolerance for the formation of amides by reaction of Grignard reagents with isocyanates. Through the application of flow chemistry and the use of substoichiometric amounts of CuBr2, this process has been developed to encompass a broad range of substrates, including reactants found to be incompatible with previously published procedures. 相似文献
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Katharina Kohse‐Höinghaus Prof. Patrick Oßwald Dr. Terrill A. Cool Prof. Tina Kasper Dr. Nils Hansen Dr. Fei Qi Prof. Charles K. Westbrook Dr. Phillip R. Westmoreland Prof. 《Angewandte Chemie (International ed. in English)》2010,49(21):3572-3597
Biofuels, such as bio‐ethanol, bio‐butanol, and biodiesel, are of increasing interest as alternatives to petroleum‐based transportation fuels because they offer the long‐term promise of fuel‐source regenerability and reduced climatic impact. Current discussions emphasize the processes to make such alternative fuels and fuel additives, the compatibility of these substances with current fuel‐delivery infrastructure and engine performance, and the competition between biofuel and food production. However, the combustion chemistry of the compounds that constitute typical biofuels, including alcohols, ethers, and esters, has not received similar public attention. Herein we highlight some characteristic aspects of the chemical pathways in the combustion of prototypical representatives of potential biofuels. The discussion focuses on the decomposition and oxidation mechanisms and the formation of undesired, harmful, or toxic emissions, with an emphasis on transportation fuels. New insights into the vastly diverse and complex chemical reaction networks of biofuel combustion are enabled by recent experimental investigations and complementary combustion modeling. Understanding key elements of this chemistry is an important step towards the intelligent selection of next‐generation alternative fuels. 相似文献