- Dipole-Induced Rectification Across AgTS/SAM//Ga2O3/EGaIn Junctions
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This Article describes the relationship between molecular structure, and the rectification of tunneling current, in tunneling junctions based on self-assembled monolayers (SAMs). Molecular dipoles from simple organic functional groups (amide, urea, and thiourea) were introduced into junctions with the structure AgTS/S(CH2)nR(CH2)mCH3//Ga2O3/EGaIn. Here, R is an n-alkyl fragment (-CH2-)2?or?3, an amide group (either -CONH- or -NHCO-), a urea group (-NHCONH-), or a thiourea group (-NHCSNH-). The amide, urea, or thiourea groups introduce a localized electric dipole moment into the SAM and change the polarizability of that section of the SAM, but do not produce large, electronically delocalized groups or change other aspects of the tunneling barrier. This local change in electronic properties correlates with a statistically significant, but not large, rectification of current (r+) at ±1.0 V (up to r+ ≈ 20). The results of this work demonstrate that the simplest form of rectification of current at ±1.0 V, in EGaIn junctions, is an interfacial effect, and is caused by a change in the work function of the SAM-modified silver electrode due to the proximity of the dipole associated with the amide (or related) group, and not to a change in the width or mean height of the tunneling barrier.
- Baghbanzadeh, Mostafa,Belding, Lee,Yuan, Li,Park, Junwoo,Al-Sayah, Mohammad H.,Bowers, Carleen M.,Whitesides, George M.
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Read Online
- Isomeric anthracene diimide polymers
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N-type semiconducting polymers are attractive for organic electronics, but desirable electron-deficient units for synthesizing such polymers are still lacking. As a cousin of rylene diimides such as naphthalene diimide (NDI) and perylene diimide (PDI), anthracene diimide (ADI) is a promising candidate; its polymers, however, have not been achieved yet because of synthetic challenges for its polymerizable monomers. Herein, we present ingenious synthesis of two dibromide ADI monomers with dibromination at differently symmetrical positions of the ADI core, which are further employed to construct ADI polymers. More interestingly, the two obtained ADI polymers possess the same main-chain and alkyl-chain structures but different backbone conformations owing to varied linking positions between repeating units. This feature enables their different optoelectronic properties and film-state packing behavior. The ADI polymers offer first examples of conjugated polymer conformational isomers and are highly promising as a new class of n-type semiconductors for various organic electronics applications.
- Tu, Dandan,Yang, Qing,Yu, Shuwen,Guo, Xin,Li, Can
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Read Online
- Supporting-Electrolyte-Free Anodic Oxidation of Oxamic Acids into Isocyanates: An Expedient Way to Access Ureas, Carbamates, and Thiocarbamates
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We report a new electrochemical supporting-electrolyte-free method for synthesizing ureas, carbamates, and thiocarbamates via the oxidation of oxamic acids. This simple, practical, and phosgene-free route includes the generation of an isocyanate intermediate in situ via anodic decarboxylation of an oxamic acid in the presence of an organic base, followed by the one-pot addition of suitable nucleophiles to afford the corresponding ureas, carbamates, and thiocarbamates. This procedure is applicable to different amines, alcohols, and thiols. Furthermore, when single-pass continuous electrochemical flow conditions were used and this reaction was run in a carbon graphite Cgr/Cgr flow cell, urea compounds could be obtained in high yields within a residence time of 6 min, unlocking access to substrates that were inaccessible under batch conditions while being easily scalable.
- Petti, Alessia,Fagnan, Corentin,van Melis, Carlo G. W.,Tanbouza, Nour,Garcia, Anthony D.,Mastrodonato, Andrea,Leech, Matthew C.,Goodall, Iain C. A.,Dobbs, Adrian P.,Ollevier, Thierry,Lam, Kevin
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supporting information
p. 2614 - 2621
(2021/06/27)
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- Method for manufacturing pentamethylene diisocyanate
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The present invention provides a method for manufacturing pentamethylene diisocyanate. The method for manufacturing pentamethylene diisocyanate of the present invention manufactures intermediates by using dialkyl carbonate. By thermally decomposing the intermediates under a specific polymerization inhibitor, the method can manufacture the pentamethylene diisocyanate having excellent purity in a high yield.
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Paragraph 0064-0065; 0066-0067
(2021/05/11)
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- FLOW CHEMISTRY SYNTHESIS OF ISOCYANATES
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The disclosure provides, inter alia, safe and environmentally-friendly methods, such as flow chemistry, to synthesize isocyanates, such as methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethylxylene diisocyanate.
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Paragraph 0175; 0185-0187
(2021/06/22)
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- An investigation on practical synthesis of carboxylic acid derivatives using p-toluenesulfonyl chloride
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Carboxylic acid derivatives are well recognized as important class of reagents frequently used in the preparation of a variety of fine or special chemicals such as amides, esters, peptides, drugs, and dyes. Although several methods were developed for the preparation of these compounds, many of them present difficulties, including low yield, high reaction temperature, harsh reaction conditions, tedious work-up, and incompatibility with scale-up. Methods: The synthesis of carboxylic anhydrides is developed through the reaction of carboxylic acids with TsCl in the presence of K2CO3 and acetonitrile as a solvent under ultrasound irradiation and conventional conditions. In addition, one-pot synthesis of acyl azides was carried out in the presence of produced carboxylic anhydrides and the addition of sodium azide under identical condition. Results: A series of carboxylic anhydrides and acyl azides were synthesized using TsCl under ultrasound irradiation and conventional stirring with simple procedure, mild reaction conditions, high yields, and scale-up ability without any restriction. In most cases, the reaction under ultrasound irradiation was better in both yields and the reaction times compared to the conventional method. Conclusion: A convenient method has been developed for the preparation of carboxylic anhydrides and acyl azides under ultrasound irradiation and conventional stirring. The present method is practical and a highly effective alternative for previous reports. The major advantages of this method are: (i) simplicity of the procedure (ii) high yields and high purity of product (iii) scale-up capacity without considerable limitation in conventional system. Under ultrasound irradiation short reaction times as compared to conventional method are observed; yields are comparable to or better than conventional method.
- Eskandari, Parvin,Kazemi, Foad
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p. 431 - 439
(2017/07/24)
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- Design and synthesis of uracil urea derivatives as potent and selective fatty acid amide hydrolase inhibitors
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Fatty acid amide hydrolase (FAAH) is one of the key enzymes involved in the biological degradation of endocannabinoids, especially anandamide. Pharmacological blockage of FAAH restores the levels of endocannabinoids, providing therapeutic benefits in the management of inflammation, depression and multiple sclerosis. In this study, a series of uracil urea derivatives as FAAH inhibitors were designed and synthesized. Structural modifications at the C5 position and side chain of N-hexyl-2,4-dioxo-3,4-dihydropyrimidine-1(2H)-carboxamide (1a) led to FAAH inhibitors with improved potency and selectivity. Structure-activity relationship (SAR) studies indicated that C5 electron-withdrawing substituents were preferred for optimal potency but not for selectivity, whereas replacement of the alkyl chain with phenylalkyl moieties or biphenyl groups significantly improved both inhibitory potency and selectivity towards FAAH. Two highly potent picomolar FAAH inhibitors (4c, IC50 = 0.3 ± 0.05 nM; 4d, IC50 = 0.8 ± 0.1 nM) were developed. Compound 4c inhibited FAAH in a rapid, selective, noncompetitive, and irreversible pattern. This study provides several highly potent and selective FAAH inhibitors and an optimized chemical scaffold for the development of FAAH inhibitors. We anticipate that these FAAH inhibitors will enable new possibilities in understanding FAAH functions and development of therapeutics for pain and inflammatory diseases.
- Qiu, Yan,Ren, Jie,Ke, Hongwei,Zhang, Yang,Gao, Qi,Yang, Longhe,Lu, Canzhong,Li, Yuhang
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p. 22699 - 22705
(2017/07/10)
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- Discovery of uracil derivatives as potent inhibitors of Fatty Acid Amide Hydrolase
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Fatty Acid Amide Hydrolase (FAAH) is an intracellular serine enzyme involved in the biological degradation of the fatty acid ethanolamide family of signaling lipids, which exerts neuroprotective, anti-inflammatory, and analgesic properties. In the present study, a conjugated 2,4-dioxo-pyrimidine-1-carboxamide scaffold was confirmed as a novel template for FAAH inhibitors, based on which, a series of analogues had been prepared for an initial structure-activity relationship (SAR) study. Most of the synthesized compounds displayed moderate to significant FAAH inhibitory potency. Among them, compounds 11 and 14 showed better activity than others, with IC50 values of 21 and 53 nM. SAR analysis indicated that 2,4-dioxopyrimidine-1-carboxamides represented a novel class of potent inhibitors of FAAH, and substitution at the uracil ring or replacement of the N-terminal group might favor the inhibitory potency. Selected compounds of this class may be used as useful parent molecules for further investigation.
- Qiu, Yan,Zhang, Yang,Li, Yuhang,Ren, Jie
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- Enantioselective synthesis of 3,5-disubstituted thiohydantoins and hydantoins
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A mild method to convert optically pure amino acid thiourea and urea derivatives to thiohydantoins and hydantoins, respectively, is described. It provides an efficient way to realize enantioselective synthesis of thiohydantoins and hydantoins with good to high isolated yields and enantiomeric purities. We found that the enantiomeric purities were highly dependent on the reaction conditions including bases, solvents, and temperature.
- Chen, Yu,Su, Li,Yang, Xinying,Pan, Wenyan,Fang, Hao
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p. 9234 - 9239
(2015/11/27)
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- Semicarbazides as gel forming agents for common solvents and liquid crystals
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This paper describes the synthesis of 14 new gelling agents with semicarbazide groups as H-bonding motifs and alkyl- and/or azobenzene side groups. They gel solvents like decaline, 1,2-dichlorobenzene and toluene and liquid crystalline mixtures. X-Ray structure analysis shows that the semicarbazides are connected by H-bonds, each molecule to four neighbours. As a result a ribbon is formed with a core of H-bonded semicarbazide groups and alkyl chains sticking to the side. IR measurements show an unchanged H-bonding motif in large crystals and in the gel fibres, even in LC-mixture. During heating the gel melts (rheology), while the H-bonding motif of the crystal disappears (IR and DSC measurements). First experiments show that these gel-forming agents can be used to gel LC-phases and to stabilise the director pattern present during gel formation. The Royal Society of Chemistry 2006.
- Deindoerfer, Pia,Geiger, Thomas,Schollmeyer, Dieter,Ye, Jian Hui,Zentel, Rudolf
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p. 351 - 358
(2007/10/03)
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- A novel PdCl2/ZrO2-SO42- catalyst for synthesis of carbamates by oxidative carbonylation of amines
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At 170°C and ca. 4.0 MPa, oxidative carbonylation of aromatic amines to synthesize corresponding carbamates over a novel PdCl2/ZrO2-SO42- catalyst could proceed with high conversion and selectivity.
- Shi, Feng,Deng, Youquan,SiMa, Tianlong,Yang, Hongzhou
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p. 525 - 528
(2007/10/03)
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- Development of chiral N-alkylcarbamates as new leads for potent and selective H3-receptor antagonists: Synthesis, capillary electrophoresis, and in vitro and oral in vivo activity
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Novel carbamates as derivatives of 3-(1H-imidazol-4-yl)propanol with an N-alkyl chain were prepared as histamine H3-receptor antagonists. Branching of the N-alkyl side chain with methyl groups led to chiral compounds which were synthesized stereospecifically by a Mitsunobu protocol adapted Gabriel synthesis. The optical purity of some of the chiral compounds was determined (ee > 95%) by capillary electrophoresis (CE). The investigated compounds showed pronounced to high antagonist activity (K(i) values of 4.1-316 nM) in a functional test for histamine H3 receptors on rat cerebral cortex synaptosomes. Similar H3-receptor antagonist activities were observed in a peripheral model on guinea pig ileum. No stereoselective discrimination for the H3 receptor for the chiral antagonists was found with the in vitro assays. All compounds were also screened for central H3-receptor antagonist activity in vivo in mice after po administration. Most compounds were potent agents of the H3-receptor-mediated enhancement of brain N(τ)- methylhistamine levels. The enantiomers of the N-2-heptylcarbamate showed a stereoselective differentiation in their pharmacological effect in vivo (ED50 of 0.39 mg/kg for the (S)-derivative vs 1.5 mg/kg for the (R)- derivative) most probably caused by differences in pharmacokinetic parameters. H1- and H2-receptor activities were determined for some of the novel carbamates, demonstrating that they have a highly selective action at the histamine H3 receptor.
- Sasse, Astrid,Kiec-Kononowicz, Katarzyna,Stark, Holger,Motyl, Malgorzata,Reidemeister, Sibylle,Ganellin, C. Robin,Ligneau, Xavier,Schwartz, Jean-Charles,Schunack, Walter
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p. 593 - 600
(2007/10/03)
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- SYNTHESIS OF ALIPHATIC ISOCYANATES VIA A TWO-PHASE HOFMANN REACTION
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A convenient method of preparing aliphatic isocyanates via a two-phase Hofmann reaction using a phase transfer catalyst is described.
- Sy, Anita O.,Raksis, Joseph W.
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p. 2223 - 2226
(2007/10/02)
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- Tris(substituted amino) sulfonium salts
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Trisaminosulfonium salts of the formula (R1 R2 N)(R3 R4 N)(R5 R6 N)S+ X- wherein the R groups are alkyl of 1-20 carbons and each alkyl has at least 2 alpha hydrogens and X is selected from the group (CH3)3 SiF2, Cl, Br, I, CN, NCO, NCS NO2 and N3, are soluble in organic liquids. They are useful as polymerization catalysts and as reagents to replace other atoms or groups in organic compounds with F, Cl, Br, I, CN, NCO, NCS, NO2 or N3.
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