- Organocatalytic Claisen rearrangement: Theory and experiment
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(Chemical Equation Presented) A combined computational and experimental study on the Claisen rearrangement of a 2-alkoxycarbonyl-substituted allyl vinyl ether in the presence of thioureas as potential noncovalent organocatalysts has been performed. DFT ca
- Kirsten, Martin,Rehbein, Julia,Hiersemann, Martin,Strassner, Thomas
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- Influence of Anion-Binding Schreiner's Thiourea on DMAP Salts: Synergistic Catalysis toward the Stereoselective Dehydrative Glycosylation from 2-Deoxyhemiacetals
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Amines are used as additives to facilitate or increase the host-guest chemistry between the thiourea and the anions of Bronsted acids. However, we here demonstrate, for the first time, the synergistic effect of the combination of DMAP/HCl/Schreiner's thio
- Ghosh, Titli,Mukherji, Ananya,Kancharla, Pavan K.
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- Organophotocatalysis: Insights into the Mechanistic Aspects of Thiourea-Mediated Intermolecular [2+2]Photocycloadditions
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Mechanistic investigations of the intermolecular [2+2] photocycloaddition of coumarin with tetramethylethylene mediated by thiourea catalysts reveal that the reaction is enabled by a combination of minimized aggregation, enhanced intersystem crossing, and
- Vallavoju, Nandini,Selvakumar, Sermadurai,Pemberton, Barry C.,Jockusch, Steffen,Sibi, Mukund P.,Sivaguru, Jayaraman
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- Supramolecular relay-control of organocatalysis with a hemithioindigo-based molecular motor
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Integration of individual molecular components such as molecular motors or switches into larger meta-functional systems represents a current challenge at the forefront of molecular machine research. Here we present a modular supramolecular approach to relay the photoinduced geometry changes of a hemithioindigo based molecular motor into catalytic efficiency of a chemical reaction. Using the intrinsic chemical nature of the motor for recognition of different hydrogen-bonding organocatalysts a greater than 10-fold modulation in binding affinity is achieved upon photoisomerization. This change in affinity is then translated effectively into control of catalytic competence of the organocatalysts without direct interference by the motor. As an example the organocatalysed Michael addition reaction between nitrostyrene and 3-methoxy-dimethyl aniline was modulated in situ by visible light irradiation. Thus, dynamic and reversible remote control of catalytic processes by the switching capacity of a hemithioindigo molecular motor is established in a multicomponent chemical system. The high intrinsic modularity of this approach presents further advantages, e.g., for easy tailoring of conditions or facile exchange of catalysts and reactions. These results represent a first stepping stone into integrated chemical networks regulated by molecular machines in a fully dynamic way.
- Grill, Kerstin,Dube, Henry
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- Hydrogen-Bond Catalysis of Imine Exchange in Dynamic Covalent Systems
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The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.
- Schaufelberger, Fredrik,Seigel, Karolina,Ramstr?m, Olof
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supporting information
p. 15581 - 15588
(2020/10/02)
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- Synergetic Organocatalysis for Eliminating Epimerization in Ring-Opening Polymerizations Enables Synthesis of Stereoregular Isotactic Polyester
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Ring-opening polymerization of O-carboxyanhydrides (OCAs) can furnish polyesters with a diversity of functional groups that are traditionally hard to harvest by polymerization of lactones. Typical ring-opening catalysts are subject to unavoidable racemization of most OCA monomers, which hampers the synthesis of highly isotactic crystalline polymers. Here, we describe an effective bifunctional single-molecule organocatalysis for selective ring-opening polymerization of OCAs without epimerization. The close vicinity of both activating groups in the same molecule engenders an amplified synergetic effect and thus allows for the use of mild bases, thereby leading to minimal epimerization for polymerization. Ring-opening polymerization of manOCA monomer (OCA from mandelic acid) mediated by the bifunctional single-molecule organocatalyst yields highly isotactic poly(mandelic acid) (PMA) with controlled molecular weights (up to 19.8 kg mol-1). Mixing of the two enantiomers of PMA generates the first example of a crystalline stereocomplex in this area, which displayed distinct Tm values around 150 °C. Remarkably, the bifunctional catalysts are moisture-stable, recyclable, and easy to use, allowing sustainable and scalable synthesis of a stereoregular functional polyester.
- Tao, Youhua,Li, Maosheng,Tao, Yue,Tang, Jiadong,Wang, Yanchao,Zhang, Xiaoyong,Wang, Xianhong
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supporting information
p. 281 - 289
(2019/01/04)
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- Mechanism-Based Condition Screening for Sustainable Catalysis in Single-Electron Steps by Cyclic Voltammetry
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A cyclic-voltammetry-based screening method for Cp2TiX-catalyzed reactions is introduced. Our mechanism-based approach enables the study of the influence of various additives on the electrochemically generated active catalyst Cp2TiX, which is in equilibrium with catalytically inactive [Cp2TiX2]?. Thioureas and ureas are most efficient in the generation of Cp2TiX in THF. Knowing the precise position of the equilibrium between Cp2TiX and [Cp2TiX2]? allowed us to identify reaction conditions for the bulk electrolysis of Cp2TiX2 complexes and for Cp2TiX-catayzed radical arylations without having to carry out the reactions. Our time- and resource-efficient approach is of general interest for the design of catalytic reactions that proceed in single-electron steps.
- Liedtke, Theresa,Spannring, Peter,Riccardi, Ludovico,Gans?uer, Andreas
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supporting information
p. 5006 - 5010
(2018/03/30)
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- Stereoselective glycosylation of 2-nitrogalactals catalyzed by a bifunctional organocatalyst
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The use of a bifunctional cinchona/thiourea organocatalyst for the direct and α-stereoselective glycosylation of 2-nitrogalactals is demonstrated for the first time. The conditions are mild, practical, and applicable to a wide range of glycoside acceptors with products being isolated in good to excellent yields. The method is exemplified in the synthesis of mucin type Core 6 and 7 glycopeptides.
- Medina, Sandra,Harper, Matthew J.,Balmond, Edward I.,Miranda, Silvia,Crisenza, Giacomo E. M.,Coe, Diane M.,McGarrigle, Eoghan M.,Galan, M. Carmen
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supporting information
p. 4222 - 4225
(2016/09/09)
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- Stereoselective Koenigs–Knorr Glycosylation Catalyzed by Urea
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A stereoselective Koenigs–Knorr glycosylation reaction under the catalysis of urea is described. This method is characterized by urea-mediated hydrogen-bond activation and subsequent glycosylation with glycosyl chlorides or bromides. Excellent yields and high anomeric selectivity can be achieved in most cases. Moreover, the low α-stereoselectivity of glycosylations observed when using perbenzylated glucosyl donors can be greatly improved by the addition of tri-(2,4,6-trimethoxyphenyl)phosphine (TTMPP).
- Sun, Lifeng,Wu, Xiaowei,Xiong, De-Cai,Ye, Xin-Shan
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supporting information
p. 8041 - 8044
(2016/09/13)
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- Catalytic composition comprising proline derivative and isothiouronium salt and method of manufacturing the same
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The present invention relates to a catalyst composition comprising proline derivatives and isothiouronium salts and a preparation method thereof and, more specifically, to a catalyst composition exhibiting improved stereoselectivity by hydrogen bonding of
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Paragraph 0064-0066
(2016/11/02)
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- Method of manufacturing chiral β-hydroxy carbonyl compound and chiral β-hydroxy carbonyl compound manufactured by the same
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The present invention relates to a method for preparing a chiral β-hydroxy carbonyl compound and a chiral β-hydroxy carbonyl compound prepared thereby and, more specifically, to a method for preparing a chiral β-hydroxy carbonyl compound and a chiral β-hy
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Paragraph 0091-0094
(2016/11/17)
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- Application of "hydrogen bonding interaction" in new drug development: Design, synthesis, antiviral activity, and sars of thiourea derivatives
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A series of simple thiourea derivatives were designed based on the structure of natural product harmine and lead compound and synthesized from amines in one step. The antiviral activity of these thiourea derivatives was evaluated. Most of them exhibited significantly higher anti-TMV activity than commercial plant virucides ribavirin, harmine, and lead compound. The hydrogen bond was found to be important but not the more the better. The optimal compound (R,R)-20 showed the best anti-TMV activity in vitro and in vivo (in vitro activity, 75%/500 a??g/mL and 39%/100 a??g/mL; inactivation activity, 71%/500 a??g/mL and 35%/100 a??g/mL; curative activity, 73%/500 a??g/mL and 37%/100 a??g/mL; protection activity, 69%/500 a??g/mL and 33%/100 a??g/mL), which is significantly higher than that of Ningnanmycin. The systematic study provides strong evidence that these simple thiourea derivatives could become potential TMV inhibitors.
- Lu, Aidang,Wang, Ziwen,Zhou, Zhenghong,Chen, Jianxin,Wang, Qingmin
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p. 1378 - 1384
(2015/03/05)
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- Highly efficient isocyanate-free microwave-assisted synthesis of [6]-oligourea
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A new eco-friendly, isocyanate-free, energy-saving method for the production of [6]-oligourea, utilizing a green carbonylating agent, viz. propylene carbonate, is reported. It comprises an organocatalyzed, microwave-assisted, solvent-free synthesis. Two modes of microwave-assisted synthesis, viz. dynamic and fixed energy modes, were applied. Upon optimization, the dynamic mode gave 79% yields of [6]-oligourea. On the other hand, almost quantitative yields were obtained using the fixed mode, within 20 min, at 10 W and with the same catalyst loading. Combination of both organocatalysis and microwave energy input appears to be a key issue for the efficiency of the reaction, with the fixed energy mode being best suited. It should be noted that all data reported are reproducible (due to the homogeneous microwave technology used by CEM Discover S-Class of microwave reactors). To the best of our knowledge, this is the best eco-friendly synthetic approach for the preparation of the title oligomers. It paves the way for using more of the biorenewable and sustainable chemicals as a feedstock for the production of polyureas. The oligomer produced was analyzed by EA, ATR-FTIR, XRD, 1H and 13CNMR. Furthermore, thermal properties of the resulting [6]-oligourea were analyzed using TGA and DSC. The Royal Society of Chemistry 2013.
- Qaroush, Abdussalam K.,Al-Hamayda, Asmaa S.,Khashman, Yasmeen K.,Vagin, Sergei I.,Troll, Carsten,Rieger, Bernhard
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p. 2221 - 2226
(2013/09/02)
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- α-Selective organocatalytic synthesis of 2-deoxygalactosides
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Alpha rules: A thiourea acts as an efficient organocatalyst for the glycosylation of protected galactals to form oligosaccharides containing a 2-deoxymonosaccharide moiety (see scheme). The reaction is highly stereoselective for α-linkages and proceeds by way of a syn-addition mechanism. Copyright
- Balmond, Edward I.,Coe, Diane M.,Galan, M. Carmen,McGarrigle, Eoghan M.
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supporting information
p. 9152 - 9155
(2012/10/29)
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- Hydrogen-bonding thiourea organocatalysts: The privileged 3,5-bis(trifluoromethyl)phenyl group
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We present evidence that the privileged use of the 3,5-bis(trifluoromethyl) phenyl group in thiourea organocatalysis is due to the involvement of the ortho-CH bond in the binding event with Lewis-basic sites. We utilized a combination of low-temperature IR spectroscopy, 2D NMR spectroscopy, nano-MS (ESI) investigations, as well as density functional theory computations [M06/6-31+G(d,p), including solvent corrections as well as natural bond orbital and atoms-in-molecules analyses] to support our conclusions that bear implications for catalyst design. The present work reveals that thiourea derivatives bearing a 3,5-bis(trifluoromethyl)phenyl group interact with Lewis basic sites of carbonyl derivatives through NH and highly polarized ortho-CH interactions in hydrogen-bonded complexes. Evidence is provided through a combination of DFT, variable-temperature IR and NMR spectroscopy, as well as MS (ESI) studies.
- Lippert, Katharina M.,Hof, Kira,Gerbig, Dennis,Ley, David,Hausmann, Heike,Guenther, Sabine,Schreiner, Peter R.
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p. 5919 - 5927
(2013/01/15)
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- Click mechanochemistry: Quantitative synthesis of "ready to use" chiral organocatalysts by efficient two-fold thiourea coupling to vicinal diamines
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Mechanochemical methods of neat grinding and liquid-assisted grinding have been applied to the synthesis of mono- and bis(thiourea)s by using the click coupling of aromatic and aliphatic diamines with aromatic isothiocyanates. The ability to modify the re
- Strukil, Vjekoslav,Igrc, Marina D.,Eckert-Maksic, Mirjana,Friscic, Tomislav
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supporting information; experimental part
p. 8464 - 8473
(2012/09/05)
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- Lewis base catalysis by thiourea: N -bromosuccinimide-mediated oxidation of alcohols
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In recent times, (thio)urea derivatives have become synonymous with hydrogen bonding owing to their extensive applicability as small molecule organocatalysts. In this paper, another activation mode by thiourea derivatives, namely via Lewis base catalysis, is disclosed for the NBS-mediated oxidation of alcohols. The mild reaction conditions employed here is suitable for chemoselective oxidation of secondary alcohol in the presence of primary alcohol.
- Tripathi, Chandra Bhushan,Mukherjee, Santanu
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experimental part
p. 1592 - 1598
(2012/03/11)
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- Squaramides as potent transmembrane anion transporters
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Square peg in a round ball: Squaramides are shown to be potent transmembrane anion transporters for both chloride and bicarbonate, performing better than the thiourea and urea analogues. Studies into the nature of this transport point to a mobile carrier mechanism, where the squaramide delivers the anion cargo across the lipid bilayer (see scheme, green sphere=anion). These drug-like molecules provide a platform for the development of a new generation of anion-transport systems. Copyright
- Busschaert, Nathalie,Kirby, Isabelle L.,Young, Sarah,Coles, Simon J.,Horton, Peter N.,Light, Mark E.,Gale, Philip A.
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supporting information; experimental part
p. 4426 - 4430
(2012/06/04)
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- Silicon-(thio)urea Lewis acid catalysis
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We present a new class of catalysts based on the combination of N,N′-diaryl(thio)ureas and weak silicon Lewis acids (e.g., SiCl 4). Such silicon-(thio)urea catalysts effectively catalyze the stereospecific rearrangement of epoxides to quaternary carbaldehydes.
- Hrdina, Radim,Mueller, Christian E.,Wende, Raffael C.,Lippert, Katharina M.,Benassi, Mario,Spengler, Bernhard,Schreiner, Peter R.
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supporting information; experimental part
p. 7624 - 7627
(2011/06/26)
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- Highly diastereo- and enantioselective aldol reaction of methyl α-isocyanoacetate: A cooperative catalysis approach
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The cooperative catalyst activity between a chiral transition-metal catalyst and an achiral organocatalyst has been identified as one of the critical asymmetric reaction optimization components in the highly diastereo- and enantioselective aldol reaction
- Kim, Hun Young,Oh, Kyungsoo
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supporting information; experimental part
p. 1306 - 1309
(2011/04/26)
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- New architectures in hydrogen bond catalysis
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New achiral sulfamide, phosphoric triamide, and thiophosphoric triamide compounds have been synthesized. Their activity as hydrogen bond catalysts for the Friedel-Crafts and Baylis-Hillman reactions compares favorably with that of a known and an active th
- Rodriguez, Andrew A.,Yoo, Hoseong,Ziller, Joseph W.,Shea, Kenneth J.
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scheme or table
p. 6830 - 6833
(2010/04/29)
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- Direct reductive amination of aldehydes and ketones mediated by a thiourea derivative as an organocatalyst
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The direct reductive arylamination of arylaldehydes and ketones has been achieved using a selective imine activation by a hydrogen bond of a thiourea derivative. This mild, acid- and metal-free process requires a catalytic amount of N N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea, the Hantzsch 1,4-dihydropydine diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate as hydride source and activated 5A-molecule sieve as dehydrant. The method is adaptable for the synthesis of various amines.
- Huang, Yi-Bo,Cai, Chun
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experimental part
p. 686 - 688
(2010/03/24)
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- Acid-free, organocatalytic acetalization
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The acid-free, organocatalytic acetalization of various aldehydes and ketones with N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea is presented. The neutral, double hydrogen bonding thiourea catalyst can be used at very low loadings of 0.01-1 mol% at room temperature to furnish the respective acetals in 65-99% yield at turnover frequencies around 600 h-1. Acid-labile TBDMS-protected as well as unsaturated aldehydes can be converted efficiently into their acetals utilizing this very mild and highly practical method.
- Kotke, Mike,Schreiner, Peter R.
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p. 434 - 439
(2007/10/03)
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- Synthetic studies toward aryl-(4-aryl-4H-[1,2,4]triazole-3-yl)-amine from 1,3-diarylthiourea as urea mimetics
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A thiophile-promoted synthesis of disubstituted 4H-[1,2,4]triazole-3-yl- amines as urea mimetics from the corresponding 1,3-disubstituted thioureas has been studied, and the scope and limitations of this reaction are presented. The reaction proceeds through the formation of a carbodiimide, followed by a sequential addition-dehydration with acyl hydrazides. 1,3-Branched dialkylthioureas result in the formation of the corresponding ureas. The electronic and steric effects of the substitution on the phenyl rings of the 1,3-diarylthioureas play an important role in the formation of the intermediary carbodiimde and the direction of the subsequent ring closure of the N-acyl hydrazide adduct.
- Natarajan, Amarnath,Guo, Yuhong,Arthanari, Haribabu,Wagner, Gerhard,Halperin, Jose A.,Chorev, Michael
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p. 6362 - 6368
(2007/10/03)
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