- Mechanistic Investigations with the Aid of Isotopic Labeling, IX. Mechanism of the Ring Contraction Reaction of 1,4-Benzthiazin-2,3-4H-dione
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By 14C-labeling it is shown that the ring contraction reaction of 1,4-benzothiazin-2,3-4H-dione (1), leading via benzthiazol-2-carbonic acid (2) finally to benzthiazole (3), proceeds via hydrolytic opening of the thiolactone-bond in 1, irrespectively of H(+) or OH(-) catalysis. - (Keywords: 14C-Labeling; Ring contraction reaction; 1,4-Benzothiazin-2,3-4H-dione; Benzthiazole)
- Kollenz, Gert,Seidler, Peter
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- A Mild, General, Metal-Free Method for Desulfurization of Thiols and Disulfides Induced by Visible-Light
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A visible-light-induced metal-free desulfurization method for thiols and disulfides has been explored. This radical desulfurization features mild conditions, robustness, and excellent functionality compatibility. It was successfully applied not only to the desulfurization of small molecules, but also to peptides.
- Qiu, Wenting,Shi, Shuai,Li, Ruining,Lin, Xianfeng,Rao, Liangming,Sun, Zhankui
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supporting information
p. 1255 - 1258
(2021/05/05)
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- Unified Approach to Benzo[ d]thiazol-2-yl-Sulfonamides
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In this paper, we report a unified approach to N-substituted and N,N-disubstituted benzothiazole (BT) sulfonamides. Our approach to BT-sulfonamides starts from simple commercially available building blocks (benzo[d]thiazole-2-thiol and primary and secondary amines) that are connected via (a) a S oxidation/S-N coupling approach, (b) a S-N coupling/S-oxidation sequence, or via (c) a S-oxidation/S-F bond formation/SuFEx approach. The labile N-H bond in N-monoalkylated BT-sulfonamides (pKa (BTSO2N(H)Bn) = 3.34 ± 0.05) further allowed us to develop a simple weak base-promoted N-alkylation method and a stereoselective microwave-promoted Fukuyama-Mitsunobu reaction. N-Alkyl-N-aryl BT-sulfonamides were accessed with the help of the Chan-Lam coupling reaction. Developed methods were further used in stereo and chemoselective transformations of podophyllotoxin and several amino alcohols.
- Zále?ák, Franti?ek,Ková?, Ond?ej,Lachetová, Eli?ka,?t'astná, Nikola,Pospí?il, Ji?í
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p. 11291 - 11309
(2021/09/07)
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- Method for reducing aromatic C-N/Cl C/I bond to aromatic-H / D
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A method of reducing C an aromatic-N C/Cl/I bond to an aromatic-H / D, the process being a stable aromatic quaternary ammonium salt. After addition of the base and the solvent, the aromatic compound or the deuterated aromatic compound can be efficiently prepared by irradiation with visible light or ultraviolet light. The method can efficiently convert stable aromatic-N/I chemical bonds into aromatic-H / D bonds by visible light or ultraviolet light in a cheap and easily available solvent or deuterated solvent without using a catalyst or a transition metal compound C C. The whole production process is green, environment-friendly, low in cost, wide in substrate applicability, high in yield, high in deuterated rate, simple and convenient to operate, free of explosion risk and remarkable in advantage compared with the conventional production process.
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Paragraph 0029
(2021/09/08)
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- A substituent- And temperature-controllable NHC-derived zwitterionic catalyst enables CO2upgrading for high-efficiency construction of formamides and benzimidazoles
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Chemocatalytic upgrading of the greenhouse gas CO2 to valuable chemicals and biofuels has attracted broad attention in recent years. Among the reported approaches, N-formylation of CO2 with an amine is of great significance due to its versatility in the construction of N-containing linear and cyclic skeletons. Herein, a stable N-heterocyclic carbene-carboxyl adduct (NHC-CO2) was facilely prepared and could be used as a recyclable zwitterionic catalyst for efficient CO2 reductive upgrading via either N-formylation or further coupling with cyclization under mild conditions (25 °C, 1 atm CO2) using hydrosilane as a hydrogen source. More than 30 different alkyl and aromatic amines could be transformed into the corresponding formamides or benzimidazoles with remarkable yields (74%-98%). The electronic effect of the introduced substituent on NHC-CO2 was found to evidently affect the thermostability and nucleophilicity of the zwitterionic catalyst, which is directly correlated with its catalytic activity. Moreover, NHC-CO2 could supply CO2 by in situ decarboxylation at a specific temperature that is dependent on the introduced substituent type. Experimental and computational studies showed that the carboxyl species on NHC-CO2 was not only a nucleophilic center, but also a C1 source which rapidly captures or substitutes ambient CO2 during hydrosilylation. In addition, a simple and green conceptual process was designed for the product purification and catalyst recycling, with a good feasibility for small-scale production.
- Li, Hu,Li, Zhengyi,Wu, Hongguo,Yang, Song,Yu, Zhaozhuo,Zhang, Lilong,Zhu, Kaixun
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supporting information
p. 5759 - 5765
(2021/08/23)
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- Reductive cyclization of o-phenylenediamine with CO2 and BH3NH3 to synthesize 1H-benzoimidazole derivatives
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A simple and green protocol was developed for the reductive cyclization of o-phenylenediamine with CO2 and BH3NH3 to yield 1H-benzimidazole. The desired 1H-benzimidazole derivatives were produced under mild conditions. Mechanism investigation indicated that the coordination of o-phenylenediamine with the boron atom of BH3NH3 promoted the transfer of the formyl group to form a stable intermediate, which facilitated the intramolecular nucleophilic addition-elimination for the formation of target product. In this process, BH3NH3 served multifunctional roles, acting as a reducing agent and a formylation catalyst.
- Han, Limin,Hong, Hailong,Li, Xiao,Yang, Yue,Zhang, Junhua,Zhu, Ning
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supporting information
(2021/09/28)
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- Purification of high-purity 2-mercaptobenzothiazole by two-steps
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High-purity 2-mercaptobenzothiazole (2-MBT) is prepared from crude 2-MBT by aniline method under high pressure by solvent crystallization and deep impurity removal. For the first step of toluene purification, the semi-finished 2-MBT with excellent purity and yield can be obtained when the temperature of toluene solution reaches 100 oC and the content of toluene is about 1.5 times of that of crude 2-MBT. For the second step of deep purification, the by-products of semi-finished 2-MBT could be further removed by Na2SO3 when the mass ratio of water, the 2-MBT and Na2SO3 is 2: 1: 0.12 and the reaction condition is under 100 oC for 0.75 h. As a result, the purity and yield of 2-MBT can reach 99.9% and 97.3%, respectively. The preparation of high-purity 2-MBT would further optimize the market demand and meet the quality standard requirements for the development of other pharmaceutical intermediates or fine chemicals. This strategy solves the current problem of purification 2-MBT, and develops a new process technology route for the production of high-purity 2-MBT.
- Zhao, Zengbing,Chen, Bo,Cheng, Lanxing,Zhao, Yili,Chai, Yongli,Yang, Shucheng
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p. 851 - 859
(2021/05/19)
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- Synthesis method of benzothiazole compound
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The invention relates to a novel process for synthesizing benzothiazole compounds, which comprises the following steps of: (1) heating and stirring orthoester, o-aminothiophenol and derivatives thereof to react, monitoring the reaction process by TLC, and obtaining crude benzothiazole compounds after the reaction is finished; and (2) distilling the crude benzothiazole compound obtained in the step (1) or recrystallizing by using a solvent, and filtering to obtain the benzothiazole compound. According to the method, no solvent is added in the reaction process, the separation and purification process is optimized, and green production of fine chemicals is effectively achieved; and no catalyst is added, the operation is simple, the reaction time is remarkably shortened, the production efficiency of the product is improved, and the yield can reach 79%-90%. The problems of environmental pollution, potential safety hazards, harm to human health, resource waste and the like caused by the solvent are fundamentally solved, and the method has extremely high green industrialization value.
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Paragraph 0019-0023
(2021/07/14)
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- Iron-catalyzed tandem oxidative coupling and acetal hydrolysis reaction to prepare formylated benzothiazoles and isoquinolines
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The aldehyde group is one of the most versatile intermediates in synthetic chemistry, and the introduction of an aldehyde group into heteroarenes is important for the transformation of molecular structure. Herein, we achieved the direct formylation of benzothiazo/les and isoquinolines. The reaction features a novel iron-catalyzed Minisci-type oxidative coupling process using commercially available 1,3-dioxolane as a formylated reagent followed by acetal hydrolysis without a separation process. The reaction can be performed under exceedingly mild reaction conditions and exhibits broad functional group tolerance.
- Wu, Yue,Guo, Peng,Chen, Long,Duan, Weijie,Yang, Zengzhuan,Wang, Tao,Chen, Ting,Xiong, Fei
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supporting information
p. 3271 - 3274
(2021/04/07)
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- Photoelectrochemical cross-dehydrogenative coupling of benzothiazoles with strong aliphatic C-H bonds
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A photoelectrochemical strategy for the cross-dehydrogenative coupling of unactivated aliphatic hydrogen donors (e.g.alkanes) with benzothiazoles is reported. We used tetrabutylammonium decatungstate as the photocatalyst to activate strong C(sp3)-H bonds in the chosen substrates, while electrochemistry scavenged the extra electrons.
- Capaldo, Luca,Quadri, Lorenzo L.,Merli, Daniele,Ravelli, Davide
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supporting information
p. 4424 - 4427
(2021/05/10)
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- K2S as Sulfur Source and DMSO as Carbon Source for the Synthesis of 2-Unsubstituted Benzothiazoles
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We describe a three-component reaction of o-iodoanilines with K2S and DMSO that provides 2-unsubstituted benzothiazoles in moderate to good isolated yields with good functional group tolerance. Electron-rich aromatic amines and o-phenylenediamines instead of o-iodoanilines provided 2-unsubstituted benzothiazoles and 2-unsubstituted benzimidazoles with and without K2S under similar conditions. Notably, DMSO plays three vital roles: carbon source, solvent, and oxidant.
- Deng, Guobo,Kuang, Daizhi,Liang, Yun,Yang, Yuan,Yu, Jiangxi,Zhang, Fuxing,Zhu, Xiaoming
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supporting information
p. 3789 - 3793
(2020/06/04)
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- Direct α-Arylation of Alcohols with Aryl Halides through a Radical Chain Mechanism
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Alcohols were found to be arylated directly at their α-C?H bond with aryl halides in the presence of a base and a substoichiometric amount of t-BuOOt-Bu through a homolytic aromatic substitution mechanism. (Figure presented.).
- Aoki, Kohei,Yonekura, Kyohei,Ikeda, Yuko,Ueno, Ryota,Shirakawa, Eiji
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supporting information
p. 2200 - 2204
(2020/05/05)
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- Synthesis of Benzothiazoles via Photooxidative Decarboxylation of α-Keto Acids
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Herein, synthesis of benzothiazoles via decarboxylative cross-coupling between α-keto acids and 2-aminothiophenols under blue LED irradiation without using any photocatalyst or metal at room temperature is described. The formation of benzothiazole is driven by the EDA (electron donor-acceptor) complex formed between α-keto acid and 2-aminothiophenol. This methodology gives easy access to 2-substituted and -unsubstituted benzothiazoles in moderate to good yields. α-Keto acids and 2-aminothiophenols bearing different functional groups were easily transformed under the given conditions. (Figure presented.).
- Monga, Aparna,Bagchi, Sourav,Soni, Raj Kumar,Sharma, Anuj
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supporting information
p. 2232 - 2237
(2020/03/04)
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- METHODS FOR PREPARING FORMALDEHYDE FROM CARBON DIOXIDE
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The present disclosure provides, inter alia, methods for preparing formaldehyde from carbon dioxide using bis(silyl)acetals, methods for incorporating carbon derived from carbon dioxide into a complex organic molecule derived from formaldehyde using bis(silyl)acetals, and methods for generating an isotopologue of a complex organic molecule derived from formaldehyde using bis(silyl)acetals.
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Paragraph 0017
(2020/11/27)
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- A General Photocatalytic Route to Prenylation
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Prenylation is an essential reaction on which nature relies to modify properties of molecules and build terpenoids, but remains a challenging chemical reaction. Aiming to capitalize on recent advances in photocatalysis to easily and cleanly generate a broad range of carbon based radicals, we have developed a prenyl transfer reagent that is captured by transiently generated radicals. The reagent can be made in bulk, is bench stable, and broadly applicable such that it can be used with existing photocatalytic methods with very few changes to reaction conditions. Ultimately, this provides a true drop-in solution for prenylation, expanding the scope of substrates that can be readily prenylated.
- Rathnayake, Manjula D.,Weaver, Jimmie D.
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p. 1433 - 1438
(2019/06/13)
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- Endogenous X-C=O species enable catalyst-free formylation prerequisite for CO2reductive upgrading
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CO2, the main component of greenhouse gas, is currently developed as a promising surrogate of carbon feedstock. Among various conversion routes, CO2undergoing catalytic reduction can furnish hydrogen/energy carriers and value-added chemicals, while specific metal-containing catalysts or organocatalysts are often prerequisite for smooth proceeding of the involved reaction processes. In this work, both formic acid and N-containing benzoheterocyclic compounds (including various benzimidazoles, benzothiazole, and benzoxazole) along with silanols could be synthesized with high yields (>90%) from catalyst-free reductive upgrading of CO2under mild conditions (50 °C). The endogenous X-CO species, derived from the N-methyl-substituted amide-based solvent [Me2N-C(O)-R], especially PolarClean, and O-formyl group [O-C(O)-H] of in situ formed silyl formate, were found to play a prominent promotional role in the activation of the used hydrosilane for reductive CO2insertion, as demonstrated by density functional theory (DFT) calculations and isotopic labeling experiments. Moreover, reaction mechanisms and condition-based sensitivity assessment were also delineated.
- Dai, Wenshuai,Li, Hu,Saravanamurugan, Shunmugavel,Wu, Hongguo,Yang, Song
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p. 5822 - 5832
(2020/10/21)
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- Tetracoordinate borates as catalysts for reductive formylation of amines with carbon dioxide
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We report sodium trihydroxyaryl borates as the first robust tetracoordinate organoboron catalysts for reductive functionalization of CO2. These catalysts, easily synthesized from condensing boronic acids with metal hydroxides, activate main group element-hydrogen (E-H) bonds efficiently. In contrast to BX3 type boranes, boronic acids and metal-BAr4 salts, under transition metal-free conditions, sodium trihydroxyaryl borates exhibit high reactivity of reductive N-formylation toward a variety of amines (106 examples), including those with functional groups such as ester, olefin, hydroxyl, cyano, nitro, halogen, MeS-, ether groups, etc. The over-performance to catalyze formylation of challenging pyridyl amines affords a promising alternative method to the use of traditional formylation reagents. Mechanistic investigation supports electrostatic interactions as the key for Si/B-H activation, enabling alkali metal borates as versatile catalysts for hydroborylation, hydrosilylation, and reductive formylation/methylation of CO2.
- Du, Chen-Xia,Huang, Zijun,Jiang, Xiaolin,Li, Yuehui,Makha, Mohamed,Wang, Fang,Zhao, Dongmei
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supporting information
p. 5317 - 5324
(2020/09/17)
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- Transition-metal and oxidant-free approach for the synthesis of diverse N-heterocycles by TMSCl activation of isocyanides
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A highly efficient TMSCl-mediated addition of N-nucleophiles to isocyanides has been achieved. This transition-metal and oxidant-free strategy has been applied to the construction of various N-heterocyles such as quinazolinone, benzimidazole and benzothiazole derivatives by the use of distinct amino-based binucleophiles. The notable feature of this protocol includes its mild reaction condition, broad functional group tolerance and excellent yield. This journal is
- Chen, Fen-Er,Dong, Lin,Li, Hongyan,Liu, Jinxin,Luo, Liangliang,Xiao, You-Cai,Zhou, Yuan
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p. 29257 - 29262
(2020/10/02)
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- "Metal-Free" Nanoassemblies of AIEE-ICT-Active Pyrazine Derivative: Efficient Photoredox System for the Synthesis of Benzimidazoles
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Supramolecular nanoassemblies of an AIEE-ICT-active pyrazine derivative (TETPY) having strong absorption in the visible region and excellent transportability have been utilized as an efficient photoredox catalytic system for the synthesis of a variety of benzimidazoles having electron-withdrawing/electron-releasing/aliphatic groups under "metal-free"conditions. The reaction protocol involves the successful harvesting of visible light by TETPY assemblies to catalyze the coupling of o-phenylenediamine/substituted diamines and substituted aromatic/heterocyclic/aliphatic aldehydes under aerial conditions using mixed aqueous media as the reaction solvent. TETPY assemblies could activate aerial oxygen to generate superoxide for completing the vital proton abstraction step without the need for any external metal/base/oxidant. Moreover, all the products are purified by recrystallization from organic solvents. The TETPY assemblies also exhibited high efficiency in catalyzing the synthesis of 2-substituted benzothiazoles and quinazolines in excellent yields.
- Dadwal, Shruti,Kumar, Manoj,Bhalla, Vandana
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p. 13906 - 13919
(2020/11/20)
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- Nanolayered cobalt-molybdenum sulphides (Co-Mo-S) catalyse borrowing hydrogen C-S bond formation reactions of thiols or H2S with alcohols
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Nanolayered cobalt-molybdenum sulphide (Co-Mo-S) materials have been established as excellent catalysts for C-S bond construction. These catalysts allow for the preparation of a broad range of thioethers in good to excellent yields from structurally diverse thiols and readily available primary as well as secondary alcohols. Chemoselectivity in the presence of sensitive groups such as double bonds, nitriles, carboxylic esters and halogens has been demonstrated. It is also shown that the reaction takes place through a hydrogen-autotransfer (borrowing hydrogen) mechanism that involves Co-Mo-S-mediated dehydrogenation and hydrogenation reactions. A novel catalytic protocol based on the thioetherification of alcohols with hydrogen sulphide (H2S) to furnish symmetrical thioethers has also been developed using these earth-abundant metal-based sulphide catalysts.
- Corma, Avelino,Sorribes, Iván
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p. 3130 - 3142
(2019/03/13)
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- Selective Conversion of Carbon Dioxide to Formaldehyde via a Bis(silyl)acetal: Incorporation of Isotopically Labeled C1 Moieties Derived from Carbon Dioxide into Organic Molecules
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The conversion of carbon dioxide to formaldehyde is a transformation that is of considerable significance in view of the fact that formaldehyde is a widely used chemical, but this conversion is challenging because CO2 is resistant to chemical transformations. Therefore, we report here that formaldehyde can be readily obtained from CO2 at room temperature via the bis(silyl)acetal, H2C(OSiPh3)2. Specifically, formaldehyde is released from H2C(OSiPh3)2 upon treatment with CsF at room temperature. H2C(OSiPh3)2 thus serves as a formaldehyde surrogate and provides a means to incorporate CHx (x = 1 or 2) moieties into organic molecules. Isotopologues of H2C(OSiPh3)2 may also be synthesized, thereby providing a convenient means to use CO2 as a source of isotopic labels in organic molecules.
- Rauch, Michael,Strater, Zack,Parkin, Gerard
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supporting information
p. 17754 - 17762
(2019/11/05)
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- Method for synthesizing benzothiazole by microwave radiation of benzothioamide compound in aqueous phase
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The invention discloses a method for synthesizing benzothiazole by microwave radiation of a benzothioamide compound in an aqueous phase. The method includes the steps: adding the benzothioamide compound into the aqueous phase under microwave conditions; performing cyclization under alkaline conditions to generate the benzothiazole. The method for preparing the benzothiazole is environmentally friendly, simple and convenient in operation, safe, cheap and efficient. Compared with the prior art, the method is applicable to a lot of functional groups, high in yield, few in by-products, simple in operation, safe, low in cost and environmentally friendly.
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Paragraph 0013
(2019/02/13)
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- Cobalt-catalyzed synthesis of N-containing heterocycles: Via cyclization of ortho -substituted anilines with CO2/H2
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The CO2-involved synthesis of chemicals is of great significance from the green and sustainable chemistry viewpoint. Herein, we report a non-noble metal catalytic system composed of CoF2, CsF and P(CH2CH2PPh2)3 (denoted as PP3) for the synthesis of N-containing heterocycles from ortho-substituted anilines and CO2/H2. Mechanism investigation indicates that [Co(PP3)H(CO2)]+ is a catalytically active intermediate under working conditions; and CsF plays important roles in activating ortho-substituted anilines via hydrogen bond interactions, thus promoting the formation of the final products. This catalytic system is highly efficient, and allows a wide scope of ortho-substituted anilines, together with excellent functional group tolerance, affording various N-containing heterocycles in good to excellent yields.
- Ke, Zhengang,Yu, Bo,Wang, Huan,Xiang, Junfeng,Han, Juanjuan,Wu, Yunyan,Liu, Zhenghui,Yang, Peng,Liu, Zhimin
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supporting information
p. 1695 - 1701
(2019/04/10)
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- The dilemma between acid and base catalysis in the synthesis of benzimidazole from: O -phenylenediamine and carbon dioxide
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The tandem synthesis of benzimidazole and other azoles can be achived by the N-formylation of ortho-substituted anilines followed by a cyclization reaction. However, CO2-based N-formylations with hydrosilane reducing agents are base catalyzed whereas the cyclization reaction is acid catalyzed. The mismatch in catalytic conditions means that only one of the steps can be catalyzed in a single pot reaction. While the N-formylation reaction is frequently the target of catalyst development, the cyclization reaction requires comparably much harsher reaction conditions. Identification of these difficulties lead us to the development of a one-pot, two-step synthesis of benzimidazole under mild reaction conditions employing acid catalysts.
- Hulla, Martin,Nussbaum, Simon,Bonnin, Alexy R.,Dyson, Paul J.
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p. 13089 - 13092
(2019/11/11)
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- Catalytic synthesis of benzimidazoles and organic carbamates using a polymer supported zinc catalyst through CO2 fixation
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Utilization of carbon dioxide in chemical fixation for synthesis of fine chemicals like benzimidazoles, organic carbamates, etc. is in high demand in recent years as carbon dioxide is a cost effective, sustainable, and green renewable C1 source. In this article we present the design and synthesis of an organically modified polystyrene bound heterogeneous [PS-Zn(ii)-SALTETA] catalyst. The catalyst has been characterized thoroughly by Fourier transform infrared spectroscopy, atomic absorption spectroscopy, thermo gravimetric analysis, PXRD, SEM and EDAX studies. The catalyst was used for cyclization of o-phenylenediamines through insertion of carbon dioxide in order to produce benzimidazoles in the presence of dimethylamine borane (DMAB). The developed catalytic procedure is sustainable, economical and efficient owing to the utilization of ethanol/water as a biodegradable and environment friendly solvent system. Besides benzimidazole production the catalyst was also very active for manufacture of organic carbamates from anilines and n-butyl bromide under atmospheric CO2 pressure under solvent free conditions at room temperature and the catalytic protocol showed outstanding functional group tolerance. Moreover the catalyst is highly recyclable and reusable.
- Biswas, Imdadul Haque,Biswas, Surajit,Islam, Md Sarikul,Riyajuddin, Sk,Sarkar, Priyanka,Ghosh, Kaushik,Islam, Sk Manirul
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p. 14643 - 14652
(2019/09/30)
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- Graphene Oxide: A Metal-Free Carbocatalyst for the Synthesis of Diverse Amides under Solvent-Free Conditions
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An environmentally friendly, inexpensive, carbocatalyst, graphene oxide (GO) promoted efficient, metal-free transamidation of various carboxamides with aliphatic, cyclic, and aromatic amines is demonstrated. The protocol is equally applicable to phthalimide, urea, and thioamide determining its adaptability. The oxygenated functionalities such as carbonyl (?C=O), epoxy (?O?), carboxyl (?COOH) and hydroxyl (?OH), present on graphene oxide surface impart acidic properties to the catalyst. The graphene oxide being heterogeneous in nature, work efficiently under solvent-free reaction conditions providing desired products in good to excellent yields. The one-pot synthesis of 2,3-Dihydro-5H-benzo[b]-1,4-thiazepin-4-one moiety by GO catalyzed Aza Michael addition followed by intramolecular transamidation is also described. A plausible reaction mechanistic pathway involving H-bonding is discussed. The graphene oxide can be recycled and reused up to five cycles without much loss in catalytic activity. (Figure presented.).
- Patel, Khushbu P.,Gayakwad, Eknath M.,Patil, Vilas V.,Shankarling, Ganapati S.
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supporting information
p. 2107 - 2116
(2019/03/26)
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- Hydrogen bonding promoted simple and clean photo-induced reduction of C-X bond with isopropanol
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We herein report a simple and clean photo-induced metal-free reduction of C-X bond under an atmosphere of air at room temperature. Isopropanol is used as both the reducing reagent and solvent. Various functional groups (acids, esters, alcohols, anilines, phenols, indoles, pyridines, cyano and trifluoromethyl groups) and other heterocyclic compounds are tolerated. Different organic halides (including C-I, C-Br and C-Cl bonds) can be dehalogenated with moderate to excellent yields. Polyhalides are also reduced chemoselectively and efficiently. DFT calculation suggests a six-membered ring transition state via C-X H-O hydrogen bonding to decrease the activation energy.
- Cao, Dawei,Yan, Chaoxian,Zhou, Panpan,Zeng, Huiying,Li, Chao-Jun
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supporting information
p. 767 - 770
(2019/01/21)
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- Flow hydrodediazoniation of aromatic heterocycles
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Continuous flow processing was applied for the rapid replacement of an aromatic amino group with a hydride. The approach was applied to a range of aromatic heterocycles, confirming the wide scope and substituent-tolerance of the processes. Flow equipment was utilized and the process optimised to overcome the problematically-unstable intermediates that have restricted yields in previous studies relying on batch procedures. Various common organic solvents were investigated as potential hydride sources. The approach has allowed key structures, such as amino-pyrazoles and aminopyridines, to be deaminated in good yield using a purely organic-soluble system.
- R?der, Liesa,Nicholls, Alexander J.,Baxendale, Ian R.
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- Desulfurization method of organic compounds containing mercapto or disulfide bond
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The invention relates to a desulfurization method of organic compounds, in particular, organic compounds containing mercapto or a disulfide bond. The method comprises following steps: dissolving organic compounds containing mercapto or a disulfide bond by a solvent; adding a phosphine reagent and an initiator; and carrying out reactions in the presence of light to convert the substrate into corresponding desulfurization products. The organic compounds containing mercapto or a disulfide bond is R-SH or R-S-S-R; wherein R represents a primary carbon group, a secondary carbon group, a tertiary carbon group, an aryl group, or an acyl group. The reactions do not need any metal, and the reaction conditions are mild. Moreover, the desulfurization method has the advantages of high yield, wide substrate application range, and multiple suitable solvents, and is widely suitable for multiple kinds of mercapto-removing reactions and desulfurization reactions of disulfide.
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Paragraph 0026
(2019/10/01)
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- Structures, Spectroscopic Properties, and Dioxygen Reactivity of 5- and 6-Coordinate Nonheme Iron(II) Complexes: A Combined Enzyme/Model Study of Thiol Dioxygenases
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The synthesis of four new FeII(N4S(thiolate)) complexes as models of the thiol dioxygenases are described. They are composed of derivatives of the neutral, tridentate ligand triazacyclononane (R3TACN; R = Me, iPr) and 2-aminobenzenethiolate (abtx X = H, CF3), a non-native substrate for thiol dioxygenases. The coordination number of these complexes depends on the identity of the TACN derivative, giving 6-coordinate (6-coord) complexes for FeII(Me3TACN)(abtx)(OTf) (1: X = H; 2: X = CF3) and 5-coordinate (5-coord) complexes for [FeII(iPr3TACN)(abtx)](OTf) (3: X = H; 4: X = CF3). Complexes 1-4 were examined by UV-vis, 1H/19F NMR, and M?ssbauer spectroscopies, and density functional theory (DFT) calculations were employed to support the data. M?ssbauer spectroscopy reveals that the 6-coord 1-2 and 5-coord 3- 4 exhibit distinct spectra, and these data are compared with that for cysteine-bound CDO, helping to clarify the coordination environment of the cys-bound FeII active site. Reaction of 1 or 2 with O2 at -95 °C leads to S-oxygenation of the abt ligand, and in the case of 2, a rare di(sulfinato)-bridged complex, [Fe2III(μ-O)((2-NH2)p-CF3C6H3SO2)2](OTf)2 (5), was obtained. Parallel enzymatic studies on the CDO variant C93G were carried out with the abt substrate and show that reaction with O2 leads to disulfide formation, as opposed to S-oxygenation. The combined model and enzyme studies show that the thiol dioxygenases can operate via a 6-coord FeII center, in contrast to the accepted mechanism for nonheme iron dioxygenases, and that proper substrate chelation to Fe appears to be critical for S-oxygenation.
- Gordon, Jesse B.,McGale, Jeremy P.,Prendergast, Joshua R.,Shirani-Sarmazeh, Zahra,Siegler, Maxime A.,Jameson, Guy N. L.,Goldberg, David P.
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p. 14807 - 14822
(2018/11/03)
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- Synthesis of 1H-1,3-benzimidazoles, benzothiazoles and 3H-imidazo[4,5-c]pyridine using DMF in the presence of HMDS as a reagent under the transition-metal-free condition
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An operationally simple method for synthesis of benzimidazole and 3H-imidazo[4,5-c]pyridine from o-phenylenediamine or pyridine-3, 4-diamine and N,N-dimethylformamide (DMF) in the presence of hexamethyldisilazane (HMDS) as a reagent is described. To evaluate the scope of application of this reagent, it was also used to prepare benzothiazole, 1H-perimidine, and benzoxazole, which was successful for benzothiazole and 1H-perimidine but benzoxazole was not formed. This reaction complies with the principles of green chemistry as it does not use toxic solvents, transition metals, or strong acids. The products are obtained in moderate to excellent yields.
- Mostafavi, Hamid,Islami, Mohammad Reza,Ghonchepour, Ehsan,Tikdari, Ahmad Momeni
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p. 2973 - 2978
(2018/10/02)
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- A catalyst-free and additive-free method for the synthesis of benzothiazolethiones from: O -iodoanilines, DMSO and potassium sulfide
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Under catalyst-free and additive-free conditions, a novel, convenient, eco-friendly method for the synthesis of benzothiazolethiones has been developed. The three-component reaction of o-iodoanilines and K2S with DMSO proceeded smoothly and the corresponding benzothiazolethiones were obtained with good isolated yields. Meanwhile, this method could be used for the synthesis of thioureas from primary diamines. Furthermore, mechanism research showed that DMSO not only functioned as a carbon source, but also as a mild oxidant in this reaction.
- Zhu, Xiaoming,Li, Wenguang,Luo, Xiai,Deng, Guobo,Liang, Yun,Liu, Jianbing
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p. 1970 - 1974
(2018/05/23)
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- Visible-Light-Induced Difluoropropargylation Reaction with Benzothiazoline as a Reductant
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The difluoropropargyl group is a useful moiety for biological applications such as in vivo click chemistry for molecular imaging techniques. Silyl-protected bromodifluoropropyne is an important difluoropropargylation reagent with previously unexplored radical reactivity. Herein, we report visible-light-induced thiyl-radical-catalyzed hydrodifluoropropargylation reactions between silyl-protected bromodifluoropropyne and alkenes in the presence of benzothiazoline as a critical reductant. (Figure presented.).
- Chen, Jingzhi,Huang, Wenhao,Li, Ying,Cheng, Xu
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supporting information
p. 1466 - 1472
(2018/02/26)
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- Mechanistic Aspects of Pincer Nickel(II)-Catalyzed C-H Bond Alkylation of Azoles with Alkyl Halides
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The quinolinyl-based pincer nickel complex, κN,κN,κN-{C9H6N-(μ-N)-C6H4-NMe2}NiCl [(QNNNMe2)NiCl; (1)] has recently been demonstrated to be an efficient and robust catalyst for the alkylation of azoles with alkyl halides under copper-free conditions. Herein, we report the detailed mechanistic investigation for the alkylation of azoles catalyzed by (QNNNMe2)NiCl (1), which highlights an iodine-atom transfer (IAT) mechanism for the reaction involving a NiII/NiIII process. Deuterium labeling experiments indicate reversible cleavage of the benzothiazole C-H bond, and kinetic studies underline a fractional negative rate order with the substrate benzothiazole. The involvement of an alkyl radical during the alkylation is validated by radical clock and external additive experiments. An active intermediate species (QNNNMe2)Ni(benzothiazolyl) (5a) has been isolated and structurally characterized. The complex (QNNNMe2)Ni(benzothiazolyl) (5a) is found to be the resting state of catalyst 1. Kinetic analysis of electronically different intermediates suggests that the step involving the reaction of 5a with alkyl iodide is crucial and a rate-influencing step. DFT calculations strongly support the experimental findings and corroborate an IAT process for the alkylation reaction.
- Patel, Ulhas N.,Jain, Shailja,Pandey, Dilip K.,Gonnade, Rajesh G.,Vanka, Kumar,Punji, Benudhar
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supporting information
p. 1017 - 1025
(2018/03/30)
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- Oxalic/malonic acids as carbon building blocks for benzazole, quinazoline and quinazolinone synthesis
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An oxidant, base and metal free methodology has been developed for the synthesis of various 2-substituted and non-substituted benzazoles, quinazolines and quinazolinones using oxalic/malonic acids as an in situ carbon source. This methodology is applicable for a wide range of substituted o-phenylenediamine, o-aminothiophenol, o-aminophenol and o-aminobenzamide containing various functional groups and provides good to excellent yields of the corresponding product. Furthermore an easy workup procedure, high yield and easy isolation of products are key features of this methodology. The developed protocol is also applicable for the gram scale synthesis of benzimidazoles.
- Sharma, Saurabh,Bhattacherjee, Dhananjay,Das, Pralay
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supporting information
p. 1337 - 1342
(2018/03/06)
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- Nanoporous TiO2 containing an ionic liquid bridge as an efficient and reusable catalyst for the synthesis of: N, N ′-diarylformamidines, benzoxazoles, benzothiazoles and benzimidazoles
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In this work, a green and efficient procedure is reported for the preparation of N,N'-diarylformamidines, benzoxazoles, benzothiazoles, and benzimidazoles using nanoporous TiO2 containing an ionic liquid bridge. This reagent is prepared via the modification of nanoporous TiO2 with bis-3-(trimethoxysilylpropyl)-ammonium hydrogen sulfate (TiO2-[bip]-NH2+ HSO4-). The procedure gave the products in excellent yields in very short reaction times under solvent-free conditions. The reusability of the catalyst is the other important feature of the reported method.
- Mazloumi,Shirini,Goli-Jolodar,Seddighi
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p. 5742 - 5752
(2018/04/23)
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- Lewis Base Promoted Reduction of CO2 with BH3NH3 into Boryl Formates: CO2 as a Carbon Source in Organic Synthesis Under Mild Conditions
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Lewis base promoted selective reduction of CO2 into boryl formates by using BH3NH3 as a reductant under mild conditions has been reported. The boryl formates, generated in situ, were shown to be reactive and versatile sources of formyl compounds to create new C–N, C–O, and C–C bonds. The reactivity of the boryl formates to yield formic acid, formamides, formates, secondary alcohols, and benzoheterocyclic rings was investigated.
- Zhang, Bo,Du, Gaixia,Hang, Wei,Wang, Sheng,Xi, Chanjuan
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supporting information
p. 1739 - 1743
(2018/04/24)
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- Dimethyl sulfoxide-accelerated reductive deamination of aromatic amines with t-BuONO in tetrahydrofuran
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An efficient method for the conversion of aryl amines into arenes by a one-pot reductive deamination has been achieved. It was found the reductive deamination using t-BuONO in tetrahydrofuran could be accelerated by dimethyl sulfoxide and provided the deamination products with good yields under mild conditions. A plausible mechanism is discussed.
- Fang, Lu,Qi, Liang,Ye, Longfei,Pan, Zhentao,Luo, Wenjun,Ling, Fei,Zhong, Weihui
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p. 579 - 583
(2018/11/27)
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- ELECTROLYTE SOLUTION AND ELECTROCHEMICAL DEVICE
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The present invention aims to provide an electrolyte solution containing a quaternary ammonium salt as an electrolyte salt and is capable of providing an electrochemical device having a high capacitance retention and reducing generation of gas. The electrolyte solution of the present invention contains a solvent, a quaternary ammonium salt, and a nitrogen-containing unsaturated cyclic compound. The unsaturated cyclic compound is a nitrogen-containing unsaturated heterocyclic compound. The unsaturated cyclic compound excludes salts of the unsaturated cyclic compound and ionic liquids obtainable from the unsaturated cyclic compound.
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- Synthesis of benzothiazoles from 2-aminobenzenethiols in the presence of a reusable polythiazolium precatalyst under atmospheric pressure of carbon dioxide
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Synthesis of benzothiazoles from 2-aminobenzenethiols and carbon dioxide was carried out using poly(3,4-dimethyl-5-vinylthiazolium) iodide as a precatalyst to in situ generation of NHCs by deprotonation. The reaction was successfully carried out under mild conditions (1 atm of CO2 and 60–70 °C) with a broad substrate scope and functional group tolerance. The precatalyst salt was recovered and reused for several times without any loss of activity.
- Chun, Supill,Yang, Sabyuk,Chung, Young Keun
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p. 3438 - 3442
(2017/05/31)
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- N-Sulfonylcarboxamide as an Oxidizing Directing Group for Ruthenium-Catalyzed C–H Activation/Annulation
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N-Sulfonylcarboxamides can act as both a directing group for C–H activation and an internal oxidant in the Ru-catalyzed annulation reaction with alkynes to give isoquinolones. Of all of the N-sulfonylcarboxamides that were studied, the N-(2,6-difluorophenyl)sulfonamide derivatives were found to be the most efficient and led to the formation of an unstable sulfinate byproduct that decomposed into 1,3-difluorobenzene under the reaction conditions. The described isoquinolone synthesis provides an alternative to the currently known traceless annulations of hydroxamic acid and sulfoximine derivatives.
- Petrova, Elina,Rasina, Dace,Jirgensons, Aigars
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supporting information
p. 1773 - 1779
(2017/04/13)
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- Synthesis of benzimidazoles from o-phenylenediamines and DMF derivatives in the presence of PhSiH3
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A simple approach to preparation of benzimidazoles from o-phenylenediamines and DMF derivatives, only employing PhSiH3 as promoter without any other additives, was reported. This route provided moderate to high yields with a broad substrate scope. A plausible mechanism for the reaction is proposed based on the spectroscopic characterization (e.g., HRMS and 1H NMR) of the reaction mixture.
- Zhu, Jianhua,Zhang, Zhenbei,Miao, Chengxia,Liu, Wei,Sun, Wei
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p. 3458 - 3462
(2017/05/31)
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- N-Iodosuccinimide involved one-pot metal-free synthesis of 2-heteroaromatic benzothiazole compounds
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A one-pot protocol for the synthesis of structurally diverse 2-hetarylbenzothiazoles via oxidative condensation of the sp3 C-H bond with benzothiazoles has been described. This process is metal free and operationally simple. A series of 2-hetarylbenzothiazoles were prepared in moderate to good yield under mild conditions.
- Chu, Xianglong,Duan, Tiantian,Liu, Xuan,Feng, Lei,Jia, Jiong,Ma, Chen
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supporting information
p. 1606 - 1611
(2017/02/23)
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- Salicylic Acid-Catalyzed One-Pot Hydrodeamination of Aromatic Amines by tert-Butyl Nitrite in Tetrahydrofuran
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A significant acceleration in the hydrodeamination of in situ formed diazonium salts (from aromatic amines) has been observed in the presence of 10-mol% salicylic acid, using tetrahydrofuran as the hydrogen donor. The reaction proceeds efficiently at 20 °C for a wide range of substituted anilines, even at 10-mmol scale, without any other additive. The same protocol has been adapted to the selective deuterodeamination of some aromatic amines. Control experiments clearly show that aryl radicals are involved in the reaction mechanism. (Figure presented.).
- Felipe-Blanco, Diego,Alonso, Francisco,Gonzalez-Gomez, Jose C.
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supporting information
p. 2857 - 2863
(2017/08/23)
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- The synthesis of nebularine and its analogs via oxidative desulfuration in aqueous nitric acid
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The synthesis of nebularine and its analogs has been achieved via oxidative desulfuration in H2O for the first time. With 50% HNO3as an oxidant and solvent, 18 products were obtained in good yields (70%–94%). The oxidative desulfuration system could tolerate different functional groups including fluoro, chloro, amino, alkyl, allyl, ribosyl, deoxyribosyl, and arabinofuranosyl groups.More importantly, the drug nebularine could be obtained successfully on a 20 g scale, which made this route more attractive for industrial applications.
- Xia, Ran,Sun, Li-Ping,Qu, Gui-Rong
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- Iodine-catalyzed formation of substituted 2-aminobenzothiazole derivatives in PEG400
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An iodine-catalyzed formation of substituted 2-aminobenzothiazole derivatives is herein described using hydrogen peroxide as an oxidant in PEG400. The method enabled an efficient environmentally sound access to this valuable scaffold in moderate to excellent yields under metal-free conditions.
- Dumonteil,Hiebel,Scherrmann,Berteina-Raboin
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p. 73517 - 73521
(2016/08/19)
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- Metal-Free Oxidative Deamination Cross-Coupling of Imidazo-heterocycles with 2-Aminobenzothiazoles
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A metal-free oxidative deamination-cross-coupling of imidazoheterocycles with 2-aminobenzothiazoles in the presence of tert-butyl nitrite is reported for the first time. This simple protocol tolerates a wide range of functional groups to afford various benzothiazole-imidazoheterocycles in moderate to excellent yields, with the release of nitrogen and water as benign byproducts.
- Ji, Xiao-Ming,Xu, Li,Yan, Yun,Chen, Fan,Tang, Ri-Yuan
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supporting information
p. 687 - 696
(2016/02/27)
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- Atmospheric CO2 promoted synthesis of N-containing heterocycles over B(C6F5)3 catalyst
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B(C6F5)3 combined with atmospheric CO2 was found to be highly effective for the cyclization of ortho-substituted aniline derivatives with N,N-dimethylformamide (DMF), and a series of N-containing heterocycles including benzothiazoles, benzimidazoles, quinazolinone and benzoxazole were obtained in good to excellent yields.
- Gao, Xiang,Yu, Bo,Mei, Qingqing,Yang, Zhenzhen,Zhao, Yanfei,Zhang, Hongye,Hao, Leiduan,Liu, Zhimin
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p. 8282 - 8287
(2016/10/11)
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- Carbon Dioxide Mediated Novel Synthesis of Quinazoline-2,4(1H,3H)-dione in Water
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A novel, efficient, and scalable CO2 mediated synthesis of quinazoline-2,4(1H,3H)-dione was developed by a simple cyclization of 2-aminobenzonitrile with DMF in water as the solvent. This is the first report of its kind. DMF was used as the necessary carbon source in the synthesis of quinazoline-2,4(1H,3H)-dione. This synthetic protocol is very efficient; it gives >99% conversion with excellent selectivity. The product was isolated by filtration because of the highly insoluble nature of quinazoline-2,4(1H,3H)-dione in water. The co-product, dimethyl amine, also has industrial importance, and the CO2 that is used can be recycled. This protocol has wide-spread applications in the syntheses of benzimidazole and benzothiazole.
- Rasal, Kalidas B.,Yadav, Ganapati D.
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p. 2067 - 2073
(2016/12/24)
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