- Phytochemical Investigation of Iphiona aucheri. Structural Revision of Donine
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Investigation of an extract of Iphiona aucheri afforded compounds 1–3. These compounds were identified by detailed spectroscopic and spectrometric analysis, however, a literature search revealed that NMR and mass data similar to those of compound 3 have been reported for donine alkaloid 4. Investigation of the experimental and calculated NMR data of compound 4 revealed that the proposed structure should be revised to 3. This was further confirmed by synthesis of compounds 3 and 4.
- Dashti, Yousef,Hobson, Christian,Tajabadi, Fatemeh Mazraati,Rezadoost, Hassan
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- Synthesis, antimicrobial and antioxidant activity of bis sulfonamide/carbamate derivatives of bis-(4-aminophenyl) methane
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A series of new bis sulfonamide/carbamate derivatives of bis-(4-aminophenyl)methane 3(a–d)/5(a–f) were synthesized from bis-(4-aminophenyl)methane (1) using various pharmacologically active sulfonyl chlorides 2(a–d) and carbonochloridates 4(a–f) in high yields. The structures of all the newly synthesized compounds were characterized by the Infrared spectroscopy, NMR (1H and 13C), mass, and elemental analyses. Further, all the synthesized compounds were tested for the antioxidant activity by using 2, 2-diphenyl-1-picrylhydrazyl, NO, and H2O2 scavenging methods and antimicrobial activity. Most of the compounds exhibited good antioxidant and antimicrobial activities.
- Nagalakshmamma, Vadabingi,Varalakshmi, Mavallur,Umapriya, Kollu,Venkataswamy, Mallepogu,Venkataramaiah, Chintha,Thyaga Raju, Kedam,Chalapathi, Ponne Venkata,NagaRaju, Chamarthi
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p. 1289 - 1295
(2020/02/11)
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- Mechanistic Study of Stress Relaxation in Urethane-Containing Polymer Networks
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Cross-linked polymers are used in many commercial products and are traditionally incapable of recycling via melt reprocessing. Recently, tough and reprocessable cross-linked polymers have been realized by incorporating cross-links that undergo associative exchange reactions, such as transesterification, at elevated temperatures. Here we investigate how cross-linked polymers containing urethane linkages relax stress under similar conditions, which enables their reprocessing. Materials based on hydroxyl-terminated star-shaped poly(ethylene oxide) and poly((±)-lactide) were cross-linked with methylene diphenyldiisocyanate in the presence of stannous octoate catalyst. Polymers with lower plateau moduli exhibit faster rates of relaxation. Reactions of model urethanes suggest that exchange occurs through the tin-mediated exchange of the urethanes that does not require free hydroxyl groups. Furthermore, samples were incapable of elevated-temperature dissolution in a low-polarity solvent (1,2,4-trichlorobenzene) but readily dissolved in a high-polarity aprotic solvent (DMSO, 24 to 48 h). These findings indicate that urethane linkages, which are straightforward to incorporate, impart dynamic character to polymer networks of diverse chemical composition, likely through a urethane reversion mechanism.
- Brutman, Jacob P.,Fortman, David J.,De Hoe, Guilhem X.,Dichtel, William R.,Hillmyer, Marc A.
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p. 1432 - 1441
(2019/02/24)
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- N-Substituted carbamate synthesis using urea as carbonyl source over TiO2-Cr2O3/SiO2 catalyst
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The use of urea as an active form of carbon dioxide is a feasible way to substitute phosgene in the chemical industry. This paper reports an effective route for the synthesis of N-substituted carbamates from amines, urea and alcohols. Under the optimized reaction conditions, several important N-substituted carbamates were successfully synthesized in 95-98% yields over a TiO2-Cr2O3/SiO2 catalyst. The catalyst could be reused for several runs without deactivation. The catalysts were characterized by BET, XPS, XRD, and TPD, which suggested that the strength and amount of the acidic and basic sites might be the major reason for the high catalytic activity of TiO2-Cr2O3/SiO2.
- Wang, Peixue,Ma, Yubo,Liu, Shimin,Zhou, Feng,Yang, Benqun,Deng, Youquan
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p. 3964 - 3971
(2015/07/15)
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- Mild and high-yielding molybdenum(VI) dichloride dioxide-catalyzed formation of Mono-, Di-, Tri-, and tetracarbamates from alcohols and aromatic or aliphatic isocyanates
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Both molybdenum(VI) dichloride dioxide (MoO2Cl2) and its dimethylformamide (DMF) complex catalyze the addition of alcohols to isocyanates giving carbamates. Most additions proceeded to completion at room temperature within 20 min using as little as 0.1 mol% of the catalyst when working on a 1-mmol scale or just 100 ppm working on a 20-mmol scale. Sterically encumbered substrates reacted to completion when 1 mol% of the catalyst was employed. Diols, triols, and tetraols reacted with monoisocyanates likewise, as did monofunctional alcohols and diisocyanates. These pairings furnished di-, tri-, tetra-, and dicarbamates, respectively. Reactants, which were poorly soluble in CH2Cl2 at room temperature required elevating the temperature and possibly choosing a higher-boiling solvent (ClCH 2CH2Cl, DMF) as well. Additions of diols to diisocyanates were feasible, too, giving polycarbamates as we presume. Copyright
- Stock, Christian,Brueckner, Reinhard
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p. 2309 - 2330
(2012/11/07)
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- N-substituted carbamates syntheses with alkyl carbamates as carbonyl source over Ni-promoted Fe3O4 catalyst
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A series of catalysts of magnetic iron oxide containing Ni with different nickel content were prepared with co-precipitation method and tested in the syntheses of N-substituted carbamates from various amines and alkyl carbamates. Under the optimized reaction conditions, various N-substituted carbamates were successfully synthesized with 90-98% isolated yield. The catalyst could be recovered based on the magnetic property of the catalyst and reused for five runs without deactivation. The catalysts were characterized with X-ray photoelectron spectroscopy, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption, and Moessbauer spectroscopy analyses. The results showed that the catalytic activity may be derived from the delicate synergy between Ni and Fe species resulted in specific basic sites. Quasi in situ FT-IR and isotopic tracer revealed that the formation of substituted urea was the key step and the N-substituted carbamate was formed via further alcoholysis of the substituted urea.
- Shang, Jianpeng,Guo, Xiaoguang,Shi, Feng,Ma, Yubo,Zhou, Feng,Deng, Youquan
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experimental part
p. 328 - 336
(2011/05/14)
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- Process for preparing aromatic carbamates
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The invention is directed to a process for preparing aromatic carbamates which comprises the reaction of an aromatic amine with an organic carbonate in the presence of a catalyst characterized in that Zn4O(OAc)6 is used as catalyst.
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Page/Page column 8
(2010/10/03)
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- Novel material forming supramolecular structures, process and uses
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The invention relates to novel material, forming supramolecular structures below its transition temperature, which contains at least one C=O and/or C=S group and at least one N—H, O—H and/or S—H group and wherein the material has the structure [in-line-formulae]A(—X—B)n ??(1)[/in-line-formulae] wherein A is a cyclic, aromatic and/or aliphatic group, n being a number of 1 to 4, —X—B is, if n is 2, the same or different, and if n is 3 or 4, the same, partly the same or different and has one of the structures (2) to (4) [in-line-formulae]NH—C(Y)—Y—B ??(2)[/in-line-formulae] [in-line-formulae]—NH—C(Y)—NR—B ??(3)[/in-line-formulae] [in-line-formulae]—Y—C(Y)—NR—B ??(4)[/in-line-formulae] with Y being an Oxygen and/or Sulfur atom, B being an organic group with at least one heteroatom, where the heteroatom is bound to at least two carbon atoms when B is linear or cyclic, and where the heteroatom is bound to at least one carbon atom when B is branched, and R being a Hydrogen atom, a cyclic, aromatic and/or aliphatic group or another B group which is the same or different. The material can be made by reacting at least one isocyanate and/or thioisocyanate with at least one amine, alcohol and/or thiol. Typically, the material is used first below its transition temperature, followed by increasing the temperature to around or above the transition temperature, carrying out a process step and subsequently decrease the temperature below the transition temperature.
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Page/Page column 10-12
(2008/12/08)
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- Attempted Cycloaddition of N-Ethoxycarbonylmethyleneamine to N-Ethoxycarbonylazepine: Formation of 4,4'-Bis(ethoxycarbonylamino)diphenylmethane
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Three products were formed in the boron-trifluoride-catalysed reaction of N-ethoxycarbonylmethyleneamine with N-ethoxycarbonylazepine, N-ethoxycarbonylaniline (2), 4-(N-ethoxycarbonylaminomethyl)-N-ethoxycarbonylaniline (3), and 4,4'-bis-(N-ethoxycarbonylamino)diphenylmethane (4).Product (4) was independently synthesised.The mechanisms of formation of the products (2), (3), and (4) were established.
- Murphy, William S.,Raman, Krishna P.
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p. 447 - 448
(2007/10/02)
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