- Copper and iron-assisted palladium-catalyzed direct arylation of azoles with arylboronic acids under ligand and base-free conditions
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The direct arylation of azoles with arylboronic acids is effectively promoted by PdCl2 in the presence of copper and iron salts under ligand and base-free conditions. This reaction can be applied to heterocycles such as benzothiazole, benzoxazole, 1-methylbenzimidazole and 4,5-dimethylthiazole with moderate to good yields.
- Wu, Xiang-Mei,Shen, Qiu-Xian
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Read Online
- Synthesis of 2-Arylbenzothiazoles from Nitrobenzenes, Benzylamines, and Elemental Sulfur via Redox Cyclization
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A sustainable advanced synthetic method was developed based on redox cyclization for the synthesis of 2-arylbenzothiazoles in good to excellent yields from readily available nitrobenzenes, benzylamines, and elemental sulfur without the use of transition-metal catalysts. This method is remarkable: nitro group reduction, a benzylamine redox reaction, sulfuration, condensation, and cyclization, all proceed in a single step to generate a heterocycle. It is also highly atom-economical and does not require any external oxidizing or reducing agents.
- Imoto, Mitsutaka,Mizuno, Takumi,Nomoto, Akihiro,Ogawa, Akiya,Takeda, Motonori,Teramoto, Masahiro
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supporting information
p. 386 - 390
(2022/03/02)
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- Fast and high-efficiency synthesis of 2-substituted benzothiazoles via combining enzyme catalysis and photoredox catalysis in one-pot
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An efficient and green method, combining enzymatic and visible-light catalysis for synthesis of the widely applicable 2-substituted benzothiazoles, has been developed. This method features a relay catalysis protocol consisting of biocatalytic promiscuity
- Yang, Zeng-Jie,Gong, Qing-Tian,Yu, Yuan,Lu, Wei-Fan,Wu, Zhe-Ning,Wang, Na,Yu, Xiao-Qi
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supporting information
(2021/01/14)
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- Method for catalytically synthesizing benzothiazole compound by using copper complex
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The invention relates to a method for catalytically synthesizing benzothiazole compounds by using a copper complex, which is characterized in that a copper complex containing ortho-carborane Schiff base ligand is used as a catalyst to form aldehydes. 2 - Bromoaniline and sodium sulfide are used as raw materials, and the reaction is carried out at room temperature to obtain a benzothiazole compound. Compared with the prior art, the copper complex catalytic aldehyde, 2 -bromoaniline and sodium sulfide (Na) containing the ortho-carborane Schiff base ligand are utilized. 2 Multiple components of S) react to prepare benzothiazole compounds, and the catalyst is low in dosage, mild in reaction conditions, high in reaction rate, high in yield, wide in substrate range, cheap and accessible in raw materials and wide in application prospect in industry.
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Paragraph 0056-0067
(2021/09/22)
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- α-Keto Acids as Triggers and Partners for the Synthesis of Quinazolinones, Quinoxalinones, Benzooxazinones, and Benzothiazoles in Water
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A general and efficient method for the synthesis of quinazolinones, quinoxalinones, benzooxazinones, and benzothiazoles from the reactions of α-keto acids with 2-aminobenzamides, benzene-1,2-diamines, 2-aminophenols, and 2-aminobenzenethiols, respectively, is described. The reactions were conducted under catalyst-free conditions, using water as the sole solvent with no additive required, and successfully applied to the synthesis of sildenafil. More importantly, these reactions can be conducted on a mass scale, and the products can be easily purified through filtration and washing with ethanol (or crystallized).
- Huang, Jian,Chen, Wei,Liang, Jiazhi,Yang, Qin,Fan, Yan,Chen, Mu-Wang,Peng, Yiyuan
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p. 14866 - 14882
(2021/10/25)
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- Sulfur-Promoted Redox Cyclization of 2,2′-Dinitrodiphenyl Disulfides and Benzylamines
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This study aims to develop green and sustainable advanced synthetic methods based on redox cyclization. Elemental sulfur is shown to promote the efficient synthesis of 2-substituted benzothiazoles from 2,2′-dinitrodiphenyl disulfides and benzylamines via redox cyclization in the absence of transition-metal catalysts and solvents. The 2-substituted benzothiazoles are obtained in good to excellent yields. This synthetic methodology is highly atom-economical and does not require any external oxidizing and/or reducing agents.
- Teramoto, Masahiro,Imoto, Mitsutaka,Takeda, Motonori,Mizuno, Takumi,Nomoto, Akihiro,Ogawa, Akiya
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p. 2485 - 2493
(2021/04/15)
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- Photocatalyst- And Transition-Metal-Free Visible-Light-Promoted Intramolecular C(sp2)-S Formation
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A photocatalyst- and transition-metal-free visible-light-induced cyclization of ortho-halothiobenzanilides has been developed. Upon irradiation with visible light, substrates undergo dehalogenative cyclization to 2-aryl benzothiazoles with high efficiency and selectivity. This photocyclization exhibits a high tolerance to various functional groups, is applicable for the synthesis of 2-alkyl benzothiazoles, and is easy to set up for gram-scale reaction.
- Wang, Hao,Wu, Qi,Zhang, Jian-Dong,Li, Hai-Yan,Li, Hong-Xi
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p. 2078 - 2083
(2021/04/05)
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- Method for preparing benzothiazole compound from visible light promoted N-(2-bromophenyl) thioamide
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The invention discloses a method for preparing a benzothiazole compound from N-(2-bromophenyl) thioamide under the promotion of visible light. Specifically, under the protection of inert gas, according to the molar ratio of N-(2-bromophenyl) thioamide to inorganic base being 1: 0.5, reactants are added into a reaction container provided with a stirring device, then dimethyl sulfoxide is added, and stirring reaction is carried out for 2-24 hours at room temperature under the irradiation of visible light to obtain the benzothiazole compound. Under the condition of not adding any photosensitizer or transition metal catalyst, sodium phosphate is used as alkali, and under the irradiation of a 45W household compact fluorescent lamp, a series of intramolecular cross-coupling reactions of N-(2-bromophenyl) thioamide are realized. In addition, the benzothiazole compound can be obtained with high yield. The whole process is green, efficient and easy to operate, and the method is a good method for synthesizing the benzothiazole compound.
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Paragraph 0082-0084
(2021/06/22)
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- Visible-Light Carbon Nitride-Catalyzed Aerobic Cyclization of Thiobenzanilides under Ambient Air Conditions
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A metal-free heterogeneous photocatalysis has been developed for the synthesis of benzothiazoles via intramolecular C-H functionalization/C-S bond formation of thiobenzanilides by inexpensive graphitic carbon nitride (g-C3N4) under visible-light irradiation. This reaction provides access to a broad range of 2-substituted benzothiazoles in high yields under an air atmosphere at room temperature without addition of a strong base or organic oxidizing reagents. In addition, the catalyst was found to be stable and reusable after five reaction cycles.
- Bai, Jin,Yan, Sijia,Zhang, Zhuxia,Guo, Zhen,Zhou, Cong-Ying
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supporting information
p. 4843 - 4848
(2021/06/28)
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- NCS/TBHP promoted C2 arylation of benzothiazoles with aldehydes in DMSO
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A N-chlorosuccinimide catalyzed oxidative synthesis of 2-aryl benzothiazole from benzothiazoles and aryl aldehydes using tert-butyl peroxybenzoate as an oxidant in dimethyl sulfoxide (DMSO) has been developed in moderate to good yields. Solvent DMSO as a strong Lewis base plays an efficient role in the reaction. Various substrates were tolerated under optimized conditions affording the arylated products in 12–94% yields for 28 examples. Additionally, acylated benzothiazoles were produced with 4 examples.
- Xu, Wen-Xiu,Ye, Fei-Xia,Liu, Xing-Hai,Weng, Jian-Quan
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- Preparation method of substituted benzothiazole C2 arylated derivative
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The invention discloses a substituted benzothiazole C2 arylated derivative and a preparation method thereof. The preparation method comprises the following steps: mixing substituted benzothiazole represented by a formula (II) and substituted benzaldehyde represented by a formula (III); adding a free radical initiator N-chlorosuccinimide (NCS) and an oxidant tert-butyl hydroperoxide (TBHP), carrying out a stirring reaction for about 12 h at 120 DEG C in a nitrogen atmosphere by using DMSO as a solvent, and after the reaction is finished, separating and purifying the reaction liquid to prepare the substituted benzothiazole C2 arylated derivative represented by a formula (I). The invention provides a new method for synthesizing a benzothiazole C2 arylated derivative by taking an NCS/TBHP double component as an oxidation system through a stirring and reaction for about 12 hours at 120 DEG C in a nitrogen atmosphere under the assistance of a strong Lewis base DMSO; and according to the method, an NCS/TBHP double-component oxidation system and an aprotic solvent are selected, and the method has the advantages of being simple in catalytic system, good in product yield and wide in substrate range.
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Paragraph 0019-0020
(2020/05/02)
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- Sulfamic acid-catalyzed conversion of o-aminothiophenol and aromatic aldehydes to 2-arylbenzothiazoles
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Non-metallic, non-toxic, and cheap sulfamic acid was used as a catalyst for the synthesis of 2-arylbenzothiazole from o-aminothiophenol and aromatic aldehydes bearing electron-donating or electron-withdrawing groups. The sulfamic acid catalyst can be reus
- Shi, Chunjie,Song, Renyuan,Wang, Guangrong,Yu, Xiaofeng
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p. 871 - 879
(2020/09/09)
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- Synthesis, characterization, and applications of novel Co(II)-pyridoxal phosphate-Schiff base/SBA-15 as a nanocatalyst for the green synthesis of benzothiazole heterocycles
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Mesoporous heterogeneous santa barbara amorphous (SBA)-15-supported cobalt complex, as a novel nanocatalyst containing N–O chelating Schiff-base ligand was successfully synthesized by the reaction of SBA-15 and Cobalt(II)-Schiff-base complex. The Co(II)-S
- Yari, Hassan,Dehkharghani, Rahebeh A.,Bardajee, Ghasem R.,Akbarzadeh-T, Niloufar
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p. 1490 - 1500
(2020/03/30)
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- Photoinduced Heterogeneous C?H Arylation by a Reusable Hybrid Copper Catalyst
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Heterogeneous copper catalysis enabled photoinduced C?H arylations under exceedingly mild conditions at room temperature. The versatile hybrid copper catalyst provided step-economical access to arylated heteroarenes, terpenes and alkaloid natural products with various aryl halides. The hybrid copper catalyst could be reused without significant loss of catalytic efficacy. Detailed studies in terms of TEM, HRTEM and XPS analysis of the hybrid copper catalyst, among others, supported its outstanding stability and reusability.
- Choi, Isaac,Müller, Valentin,Lole, Gaurav,K?hler, Robert,Karius, Volker,Vi?l, Wolfgang,Jooss, Christian,Ackermann, Lutz
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supporting information
p. 3509 - 3514
(2020/03/03)
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- I2/TBHP-Mediated tandem cyclization and oxidation reaction: Facile access to 2-substituted thiazoles and benzothiazoles
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The efficient synthesis of 2-substituted thiazoles and benzothiazoles has been accomplished employing readily available cysteine esters and 2-aminobenzenethiols as N and S sources. The reaction proceeds under an I2/TBHP system and involves a on
- Liu, Li,Tan, Chen,Fan, Rong,Wang, Zihan,Du, Hongguang,Xu, Kun,Tan, Jiajing
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supporting information
p. 252 - 256
(2019/01/10)
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- Cuprous cluster as effective single-molecule metallaphotocatalyst in white light-driven C[sbnd]H arylation
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This study investigated a series of ferrocenyltelluroether based cuprous halide clusters as effective single-molecule metallaphotocatalysts (SMP) in white light-driven C[sbnd]H arylation at room temperature and air. A systematic mechanistic study reveals that Cu(I) cluster can be irradiated by visible light to promote proton-coupled electron transfer (PCET), during which the electron from Cu(I)* leaves together with the proton from benzothiazole C[sbnd]H, leading to the formation of benzothiazolate-coordinated Cu(II) intermediate and aryl radical. Subsequently, the electron transfer (ET) from the ferrocene unit to the Cu(II) center releases the reactive benzothiazolate to form the target product with aryl radical. The advantages of these copper(I) halide clusters as SMP include high photocatalytic efficiency, structure adjustability, mild reaction conditions and good functional group tolerance.
- Ji, Wei,Wang, Hao,Li, Cheng-An,Gao, Fei,An, Zhong-Fu,Huang, Ling,Wang, He,Pan, Yue,Zhu, Dun-Ru,Wang, Jian-Qiang,Guo, Cheng,Mayoral, José A.,Jing, Su
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p. 270 - 276
(2019/09/30)
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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; 0026
(2019/02/13)
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- Method used for rapid preparation of benzo-heterocycle compound with physical grinding under solvent-free room temperature conditions
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The invention discloses a method used for rapid preparation of benzo-heterocycle compound with physical grinding under solvent-free room temperature conditions. According to the method, glacial aceticacid is taken as a catalyst; at solvent-free room temperature conditions, physical grinding is adopted, reaction of 2-substituted arylamines (2-mercapto arylamine, 2-aminophenol, and o-phenylenediamine) and aromatic aldehydes is carried out using physical grinding. The method is friendly to the environment, is simple in operation, is safe, is low in cost, and is high in efficiency. Compared withthe prior art, the advantages are that: the method is suitable for a large amount of functional groups, yield is high, less by-product is generated, operation is simple, the method is safe, cost is low, and the method is friendly to the environment.
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Paragraph 0062; 0136
(2019/01/21)
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- Copper-Catalyzed Benzylic C—H Functionalization, Oxidation and Cyclization of Methylarenes: Direct Access to 2-Arylbenzothiazoles
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The direct C—H functionalization of methylarenes is of great significance. Herein, a copper-catalyzed oxidative C—N/C—S bond formation through benzylic C(sp3)—H functionalization, oxidation and cyclization of methylarenes is reported. Various 2-arylbenzothiazoles have been synthesized in moderate to excellent yields with readily available o-iodoaniline, potassium sulfide, and methylarenes as raw materials.
- Yu, Wentao,Wu, Wanqing,Jiang, Huanfeng
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p. 1158 - 1166
(2019/10/22)
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- Transition Metal-Free Oxidative Coupling of Primary Amines in Polyethylene Glycol at Room Temperature: Synthesis of Imines, Azobenzenes, Benzothiazoles, and Disulfides
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A transition metal-free protocol has been developed for the oxidative coupling of primary amines to imines and azobenzenes, thiols to disulfides, and 2-aminothiophenols to benzothiazoles, offering excellent yields. The advantageous features of the present environmentally benign methodology include the usage of biocompatible and green reaction conditions such as, solvent, room temperature reactions and transition metal-free approach. Moreover, it offers a broader substrate scope.
- Hudwekar, Abhinandan D.,Verma, Praveen K.,Kour, Jaspreet,Balgotra, Shilpi,Sawant, Sanghapal D.
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p. 1242 - 1250
(2019/01/09)
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- Exogenous Photosensitizer-, Metal-, and Base-Free Visible-Light-Promoted C-H Thiolation via Reverse Hydrogen Atom Transfer
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Visible-light-driven, intramolecular C(sp2)-H thiolation has been achieved without addition of a photosensitizer, metal catalyst, or base. This reaction induces the cyclization of thiobenzanilides to benzothiazoles. The substrate absorbs visible light, and its excited state undergoes a reverse hydrogen-atom transfer (RHAT) with 2,2,6,6-tetramethylpiperidine N-oxyl to form a sulfur radical. The addition of the sulfur radical to the benzene ring gives an aryl radical, which then rearomatizes to benzothiazole via RHAT.
- Xu, Ze-Ming,Li, Hong-Xi,Young, David James,Zhu, Da-Liang,Li, Hai-Yan,Lang, Jian-Ping
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supporting information
p. 237 - 241
(2019/01/10)
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- Silver-mediated 2-arylation/alkylation/acylation of benzothiazoles with aldehydes in water
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An efficient and environmentally benign method was developed for the facile synthesis of various 2-aryl and 2-alkyl substituted benzothiazoles in moderate to good yields, using a silver-mediated redox condensation of benzothiazoles and aldehydes in water. Furthermore, this method is also applicable to prepare 2-acyl benzothiazoles.
- Hua, Min,Wang, Chunqin,Liu, Qixing,Chen, Danyi,Fu, Hao,Zhou, Haifeng
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p. 1226 - 1237
(2018/08/06)
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- Metallaphotoredox-Mediated Csp2-H Hydroxylation of Arenes under Aerobic Conditions
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The direct hydroxylation of 2-arylpyridines and 2-arylbenzothiazoles via the merger of organic photoredox and metal catalysis is reported where 4CzIPN is used as the visible-light photocatalyst and Pd(OAc)2 as the metal catalyst. This method has been employed to synthesize organic molecules exhibiting excited-state intramolecular proton transfer properties for generating tunable luminescence responses.
- Shah, Sk. Sheriff,Paul, Amrita,Bera, Manoranjan,Venkatesh, Yarra,Singh, N. D. Pradeep
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supporting information
p. 5533 - 5536
(2018/09/21)
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- (Phosphinito)aryl benzimidazole PCN pincer palladium(II) complexes: Synthesis, characterization and catalytic activity in C–H arylation of azoles with aryl iodides
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The PCN pincer Pd(II) complexes 4a–c with (phosphinito)aryl benzimidazole ligands were conveniently synthesized by one-pot phosphorylation/palladation reaction of a (2-benzimidazolyl)-containing m-phenol derivative 3. The three complexes were well characterized by spectroscopic methods, elemental analysis and their molecular structures were further determined by X-ray single-crystal diffraction. The Pd(II) center in each complex adopts a typical distorted-square-planar geometry. With a catalyst loading of 0.25–0.5 mol%, complex 4a could effectively catalyze C–H arylation of benzothiazole, benzoxazole and thiazole with various aryl iodides in the presence of CuI as a cocatalyst.
- Wang, Cong,Li, Yang,Lu, Beibei,Hao, Xin-Qi,Gong, Jun-Fang,Song, Mao-Ping
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p. 184 - 192
(2017/11/03)
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- Method for preparing benzothiazole compound through microwave catalysis in water phase
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The invention discloses a method for preparing a benzothiazole compound through/under microwave catalysis in a water phase. A water-soluble coordination compound is used as a catalyst, and a reactionof inorganic sulfide, 2-iodoaniline and aldehyde is efficiently catalyzed through microwaves in a pure water phase. The method for preparing the benzothiazole compound is environmentally friendly, convenient to operate, safe, cheap and efficient. Compared with the prior art, the method is applied to a large quantity of functional groups, high in yield, simple to operate, safe, low in cost and environmentally friendly and produces a few byproducts.
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Paragraph 0032
(2018/05/16)
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- Pd-Catalyzed Decarbonylative C?H Coupling of Azoles and Aromatic Esters
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A decarbonylative C?H coupling of azoles and aromatic esters by palladium catalysis is described. Our previously reported Ni-catalyzed C?H coupling of azoles and aromatic esters has a significant drawback regarding the substrate scope. Herein, we employ p
- Matsushita, Kaoru,Takise, Ryosuke,Hisada, Tomoya,Suzuki, Shin,Isshiki, Ryota,Itami, Kenichiro,Muto, Kei,Yamaguchi, Junichiro
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supporting information
p. 2393 - 2396
(2018/05/30)
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- Cascade C(sp3)-S Bond Cleavage and Imidoyl C-S Formation: Radical Cyclization of 2-Isocyanoaryl Thioethers toward 2-Substituted Benzothiazoles
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A cascade radical cyclization of 2-isocyanoaryl thioethers with H-phosphorus oxides, organoboronic acids, or alkyl radical precursors has been efficiently developed, providing a novel and highly efficient methodology to structurally diverse C2-substituted benzothiazole derivatives with broad functional group tolerance and good yields. This cascade radical process achieves the first cycloaddition of an imidoyl radical from isocyanide to sulfur atom, rending C(sp2)-S bond formation.
- Yang, Wen-Chao,Wei, Kai,Sun, Xue,Zhu, Jie,Wu, Lei
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p. 3144 - 3147
(2018/05/28)
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- Elemental Sulfur-Mediated Decarboxylative Redox Cyclization Reaction: Copper-Catalyzed Synthesis of 2-Substituted Benzothiazoles
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A S 8 -mediated directed decarboxylative redox-cyclization strategy for the synthesis of 2-substituted benzothiazoles from o -iodoanilines, arylacetic acids, and elemental sulfur catalyzed by cheap copper metal has been developed. This reaction is operationally simple, ligand-free, compatible with a wide range of functional groups, and provides the desired products in good to excellent yields. In addition, a gram-scale experiment was carried out to furnish PMX 610, an antitumor drug.
- Wang, Xin,Li, Xiaotong,Hu, Renhe,Yang, Zhao,Gu, Ren,Ding, Sai,Li, Pengyi,Han, Shiqing
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supporting information
p. 219 - 224
(2017/10/09)
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- Controllable assembly of the benzothiazole framework using a CC triple bond as a one-carbon synthon
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A concise and efficient protocol to assemble diverse benzothiazole derivatives in high yields was provided via copper catalyzed tandem cyclization with o-haloanilines, elemental sulfur and terminal alkynes as raw materials. In this protocol, C atoms on the CC triple bond were controllably involved in the construction of the benzothiazole framework and multiple carbon-heteroatom bonds through divergent routes.
- Huang, Yubing,Yan, Donghao,Wang, Xu,Zhou, Peiqi,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 1742 - 1745
(2018/02/21)
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- Direct arylation of benzoazoles with aldehydes utilizing metal-organic framework Fe3O(BDC)3 as a recyclable heterogeneous catalyst
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A metal-organic framework Fe3O(BDC)3 was synthesized and used as a recyclable heterogeneous catalyst for the direct arylation of azoles with benzaldehydes. Following this protocol, inexpensive and commercially available benzaldehydes could act as an aryl source for the transformation, replacing the aryl halides normally employed in the conventional cross-coupling reactions. The catalyst disclosed higher catalytic productivity for the formation of aryl-substituted azoles than various MOFs and diverse homogeneous iron catalysts. The conversion was considerably regulated by the solvent and the oxidant, and the combination of N-methyl-2-pyrrolidone with di-tert-butyl peroxide offered the best yield. Heterogeneous catalysis was verified for the reaction, and the production of aryl-substituted azoles was only feasible in the presence of the iron framework. It was possible to reuse the catalyst for the direct arylation of azoles with aldehydes while its catalytic activity was preserved for multiple cycles. To our best judgment, this direct arylation of azoles with aldehydes utilizing solid catalysts has not been previously reported.
- Doan, Son H.,Nguyen, Khoa D.,Nguyen, Tung T.,Phan, Nam T. S.
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p. 1423 - 1431
(2017/01/21)
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- Visible-light-promoted synthesis of benzothiazoles from 2-aminothiophenols and aldehydes
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A visible-light-promoted synthesis of benzothiazoles from 2-aminothiophenols and aldehydes has been developed. A wide range of aromatic, heteroaromatic and aliphatic aldehydes were successfully applied. The benzothiazole products were prepared in good yields. The reaction was carried out in the absence of transition-metal catalysts and extra additives. A radical reaction pathway was proposed.
- Ye, Lin-miao,Chen, Jie,Mao, Peng,Mao, Zhi-feng,Zhang, Xue-jing,Yan, Ming
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supporting information
p. 874 - 876
(2017/02/18)
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- Au- and Ag-loaded MnO2 nanostructures supported on nitrogen- and nitrogen–sulfur-doped pyroproteins: Synthesis and catalytic activity in organic transformations
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Four novel Au- and Ag-loaded MnO2 nanostructures supported on nitrogen-doped pyroprotein of natural silk (Au–MnO2@PPNS and Ag–MnO2@PPNS) and nitrogen–sulfur-doped pyroprotein of natural wool (Au–MnO2@PPNW and Ag–MnO2@PPNW) have been synthesized. Nitrogen- and nitrogen–sulfur-doped pyroproteins were prepared by carbonization of natural silk and wool proteins, respectively. The catalysts were investigated for the aerobic oxidation of aromatic hydrocarbons of petroleum naphtha and the aerobic oxidative synthesis of 2-phenylbenzo[d]thiazoles, 2-phenyl-1H-benzo[d]imidazoles and 2-phenyl-4-quinazolinones in the absence of any co-promoter and additional oxidizing reagent. The prepared catalytic systems showed higher catalytic activity in comparison to aggregated catalysts.
- Hezarkhani, Zeinab,Shaabani, Ahmad
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- Development of (quinolinyl)amido-based pincer palladium complexes: A robust and phosphine-free catalyst system for C-H arylation of benzothiazoles
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(Quinolinyl)amido-ligated palladium(ii) complexes have been synthesized and applied in the catalytic C-H bond arylation of benzothiazoles. The tridentate ligand precursors R2N-C(O)CH2-(NH)-C9H6N [(R2NNN8-Q)-H; R2N = morpholinyl, Me-N-piperazinyl] and the pincer palladium complexes [κN,κN,κN-{R2N-C(O)CH2-(μ-N)-C9H6N}]PdX [(R2NNN8-Q)PdX {R2N = Et2N, morpholinyl, Me-N-piperazinyl; X = OAc or Cl}] were efficiently synthesized, and characterized by various analytical techniques. The iodo derivative (Et2NNN8-Q)PdI was obtained in excellent yield by the treatment of the complex (Et2NNN8-Q)PdCl with KI. The molecular structures of complexes (Et2NNN8-Q)Pd(OAc) (2a), (Et2NNN8-Q)PdCl (3a) and (Et2NNN8-Q)PdI (4a) were elucidated by X-ray crystallography. Complex 3a was found to be the most efficient catalyst for direct C-H bond arylation of substituted benzothiazoles with diverse aryl iodides using a mild base, K2CO3. The working catalyst system 3a is highly robust and can be recycled and reused several times for the arylation of benzothiazole without loss of catalytic activity. Preliminary mechanistic investigations using controlled studies and kinetic analysis have been performed, which greatly support a molecular mechanism for the arylation.
- Pandiri, Hanumanprasad,Soni, Vineeta,Gonnade, Rajesh G.,Punji, Benudhar
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p. 3543 - 3554
(2017/07/12)
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- Copper-Catalyzed Arylation of Benzothiazoles with Toluene Derivatives: Synthesis of 2-Arylbenzothiazole
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A copper-catalyzed reaction of benzothiazole and readily available toluene derivatives has been disclosed. This protocol is proposed to proceed through the oxidation of toluene and ring opening of benzothiazole, thus providing a new pathway for the synthesis of 2-arylbenzothiazoles..
- Li, Chengliang,Deng, Hongmei,Jin, Tao,Liu, Zhiqiang,Jiang, Ruolan,Li, Chunju,Jia, Xueshun,Li, Jian
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p. 4350 - 4356
(2017/09/12)
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- Elemental sulfur mediated cyclization via redox strategy: Synthesis of benzothiazoles from o-chloronitrobenzenes and benzyl chlorides
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A novel metal-free synthesis of 2-substituted benzothiazoles from easily available o-chloronitrobenzenes and benzyl chlorides using elemental sulfur as traceless oxidizing agent has been developed. The protocol provides a simple, efficient, and atom-economic way to access to benzothiazoles in moderate to excellent yields. And the approach exhibited good functional group tolerance.
- Wang, Xin,Miao, Dazhuang,Li, Xiaotong,Hu, Renhe,Yang, Zhao,Gu, Ren,Han, Shiqing
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supporting information
p. 5194 - 5199
(2017/07/28)
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- One-pot copper-catalyzed synthesis of 2-substituted benzothiazoles from 2-iodoanilines, benzyl chlorides and elemental sulfur
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An efficient one-pot three-component reaction of 2-iodoanilines, benzyl chlorides and elemental sulfur to form 2-substituted benzothiazoles in satisfactory yields (up to 98%) has been described. The reaction tolerated a wide range of functional groups on the aromatic ring. And heterocycle methylene chlorides substrates were also found to be compatible.
- Yang, Zhao,Hu, Renhe,Li, Xiaotong,Wang, Xin,Gu, Ren,Han, Shiqing
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supporting information
p. 2366 - 2369
(2017/05/29)
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- Atom economic palladium catalyzed novel approach for arylation of benzothiazole and benzoxazole with triarylbismuth reagents via C[sbnd]H activation
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We have developed a novel method for the direct C[sbnd]H functionalization of benzothiazole and benzoxazole using triarylbismuth reagents. The arylation proceeds using the homogeneous catalytic system PdCl2, Cu(OAc)2 and PPh3 ligand. Triarylbismuthines, which act as threefold arylating reagents, have low toxicity, are green and ecofriendly. These methodologies are particularly useful to prepare arylated benzothiazoles and benzoxazoles.
- Balsane, Kishor Eknath,Gund, Sitaram Haribhau,Nagarkar, Jayashree Milind
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- Epichlorohydrin cross-linked β -cyclodextrin: An environmental method for the synthesis of 2-arylbenzothiazoles derivatives in water
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In the present study, we report an environmentally benign synthesis of 2-arylbenzothiazoles derivatives from o-aminothiophenol and aldehydes in aqueous medium using β-cyclodextrin polymer as a catalyst and air as an oxidant. The polymer showed excellent c
- El-Remaily, Mahmoud Abd El Aleem Ali Ali,Soliman, Ahmed M. M.
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- Natural silk supported manganese dioxide nanostructures: Synthesis and catalytic activity in aerobic oxidation and one-pot tandem oxidative synthesis of organic compounds
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Manganese dioxide nanostructures were coated on natural silk (MnO2@silk) by simple immersion of the silk fibers into a KMnO4 aqueous solution. The silk was found to act as a in situ reducing agent and substrate in aqueous KMnO4 solution for the heterogeneous production of MnO2 nanostructures. The structure of synthesized catalyst was characterized by X-ray diffraction (XRD), flame atomic absorption spectroscopy (FAAS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The catalytic activity of the MnO2@silk was examined in the aerobic oxidation of alkyl arenes, alcohols, and oximes to their corresponding carbonyl compounds and a one-pot tandem oxidative two-component reaction of aromatic hydrocarbons of petroleum naphtha in the absence of any other oxidizing reagent or initiator.
- Shaabani, Ahmad,Hezarkhani, Zeinab,Badali, Elham
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p. 176 - 182
(2018/03/28)
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- Mechanistic Insights into Pincer-Ligated Palladium-Catalyzed Arylation of Azoles with Aryl Iodides: Evidence of a PdII-PdIV-PdII Pathway
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Pincer-based (R2POCNR′2)PdCl complexes along with CuI cocatalyst catalyze the arylation of azoles with aryl iodides to give the 2-arylated azole products. Herein, we report an extensive mechanistic investigation for the direct arylation of azoles involving a well-defined and highly efficient (iPr2POCNEt2)PdCl (2a) catalyst, which emphasizes a rare PdII-PdIV-PdII redox catalytic pathway. Kinetic studies and deuterium labeling experiments indicate that the C-H bond cleavage on azoles occurs via two distinct routes in a reversible manner. Controlled reactivity of the catalyst 2a underlines the iodo derivative (iPr2POCNEt2)PdI (3a) to be the resting state of the catalyst. The intermediate species (iPr2POCNEt2)Pd-benzothiazolyl (4a) has been isolated and structurally characterized. A determination of reaction rates of compound 4a with electronically different aryl iodides has revealed the kinetic significance of the oxidative addition of the C(sp2)-X electrophile, aryl iodide, to complex 4a. Furthermore, the reactivity behavior of 4a suggests that the arylation of benzothiazole proceeds via an oxidative addition/reductive elimination pathway involving a (iPr2POCNEt2)PdIV(benzothiazolyl)(Ar)I species, which is strongly supported by DFT calculations.
- Khake, Shrikant M.,Jagtap, Rahul A.,Dangat, Yuvraj B.,Gonnade, Rajesh G.,Vanka, Kumar,Punji, Benudhar
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supporting information
p. 875 - 886
(2016/04/19)
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- Photoinduced Copper-Catalyzed C-H Arylation at Room Temperature
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Room-temperature azole C-H arylations were accomplished with inexpensive copper(I) compounds by means of photoinduced catalysis. The expedient copper catalysis set the stage for site-selective C-H arylations of non-aromatic oxazolines under mild reaction conditions, and provides step-economical access to the alkaloid natural products balsoxin and texamine. Copper light: Room-temperature C-H arylations of heteroarenes were accomplished with inexpensive copper compounds by photoinduced catalysis. The expedient copper catalysis leads to site-selective C-H arylations of non-aromatic oxazolines under mild reaction conditions, and provides step-economical access to the alkaloid natural products balsoxin and texamine.
- Yang, Fanzhi,Koeller, Julian,Ackermann, Lutz
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supporting information
p. 4759 - 4762
(2016/04/19)
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- S8-Mediated Cyclization of 2-Aminophenols/thiophenols with Arylmethyl Chloride: Approach to Benzoxazoles and Benzothiazoles
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A metal-free approach to benzazoles from arylmethyl chlorides and 2-mercaptan/2-hydroxyanilines using elemental sulfur as a traceless oxidizing agent has been developed. The reactions proceeded in good to excellent yields, exhibiting good functional groups tolerance and gram-scale ability. A key mechanistic investigation indicated that the key intermediate trisulfide 6, which was characterized by NMR, HRMS and crystal X-ray crystallography, was separated in the reaction prior to the formation of the product.
- Gan, Haifeng,Miao, Dazhuang,Pan, Qiang,Hu, Renhe,Li, Xiaotong,Han, Shiqing
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supporting information
p. 1770 - 1774
(2016/07/07)
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- General copper-catalyzed coupling of alkyl-, aryl-, and alkynylaluminum reagents with organohalides
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We report the first example of a very general Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. The reactions proceed for the couplings of alkyl-, aryl-, and alkynylaluminum reagents with aryl and heteroaryl halides and vinyl bromides, affording the cross-coupled products in good to excellent yields. Both primary and secondary alkylaluminum reagents can be utilized as organometallic coupling partners. These reactions are not complicated by β-hydride elimination, and as a result rearranged products are not observed with secondary alkylaluminum reagents even for couplings with heteroaryl halides under "ligand-free" conditions. Radical clock experiment with a radical probe and relative reactivity study of Ph3Al with two haloarenes, 1-bromonaphthalene and 4-chlorobenzonitrile, having two different redox potentials indicates that the reaction does not involve free aryl radicals and radical anions as intermediates. These results combined with the result of the Hammett plot obtained by reacting Ph3Al with iodoarenes containing p-H, p-Me, p-F, and p-CF3 substituents, which shows a linear curve (R2 = 0.99) with a ρ value of +1.06, suggest that the current transformation follows an oxidative addition-reductive elimination pathway.
- Shrestha, Bijay,Thapa, Surendra,Gurung, Santosh K.,Pike, Ryan A. S.,Giri, Ramesh
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p. 787 - 802
(2016/02/18)
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- Pd/Cu-cocatalyzed reigoselective arylation of thiazole derivatives at 2-position under ligand-free conditions
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An efficient protocol for regioselective arylation of thiazole derivatives at the 2-position via palladium- and copper-catalyzed C-H bond activation under ligand-free conditions has been developed. The reaction proceeds smoothly with 1% palladium catalyst in the presence of 20% Cu(TFA)2 to furnish the desired products. The direct C-H arylation and no ligand made this method synthetically useful for the arylation of thiazoles at the 2-position.
- Gu, Jian,Cai, Chun
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p. 56311 - 56315
(2015/07/15)
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- N-Substituted Formamides as C1-Sources for the Synthesis of Benzimidazole and Benzothiazole Derivatives by Using Zinc Catalysts
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An efficient and convenient one-pot protocol has been developed for the synthesis of a variety of benzimidazole, benzoxazole, and benzothiazole derivatives. This novel approach uses various o-phenylenediamines and N-substituted formamides (C1 sources) in a zinc-catalyzed cyclization in the presence of poly(methylhydrosiloxane) to afford the corresponding derivatives as sole products in moderate to excellent yields.
- Nale, Deepak B.,Bhanage, Bhalchandra M.
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p. 2835 - 2842
(2015/12/18)
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- Copper-catalyzed solvent-free redox condensation of benzothiazoles with aldehydes or benzylic alcohols
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An efficient and practical method for the construction of 2-aryl-and 2-alkyl-substituted benzothiazoles via a copper-catalyzed redox condensation process between benzothiazoles and aldehydes or benzylic alcohols has been developed. The reaction proceeded under mild reaction conditions using environmentally benign tert-butyl hydroperoxide (TBHP) as the oxidant. A reaction mechanism involving the ring-opening of benzothiazoles initiated by the attack of acyl radical on the thiazole ring and intramolecular condensation is proposed based on the isolation of an anilide disulfide intermediate.
- Zhang, Mingliang,Lu, Wen-Ting,Ruan, Wenqing,Zhang, Hui-Jun,Wen, Ting-Bin
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p. 1806 - 1809
(2014/03/21)
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- KI-catalyzed arylation of benzothiazoles from the coupling of aryl aldehydes with benzothiazoles in neat water
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A KI-catalyzed oxidative coupling of benzothiazoles with aryl aldehydes has been developed using TBHP as an oxidant in neat water under metal free conditions. Various 2-aryl benzothiazoles were prepared in 36-79% yields for 28 examples. The mechanistic studies suggested that this transformation proceeded via a radical process. The Royal Society of Chemistry.
- Gao, Yuyu,Song, Qiuling,Cheng, Guolin,Cui, Xiuling
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supporting information
p. 1044 - 1047
(2014/02/14)
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- Iron-catalyzed arylation or aroylation of benzothiazoles with benzylic alcohols and aryl ketones
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An iron-catalyzed arylation or aroylation of benzothiazoles with alcohols and aryl ketones via an in situ cross-trapping strategy has been described. Both the use of an iron catalyst and the ratio of substrates are important for this transformation, and this reaction is sensitive to the electronic effects of the substituents.
- Wang, Jian,Zhang, Xiao-Zhuan,Chen, Shan-Yong,Yu, Xiao-Qi
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p. 245 - 250
(2014/01/06)
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- Design and development of POCN-pincer palladium catalysts for C-H bond arylation of azoles with aryl iodides
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Well-defined and efficient POCN-ligated palladium complexes have been developed for the direct C-H bond arylation of azoles with aryl iodides. The phosphinite-amine pincer ligands 1-(R2PO)-C6H4-3-(CH2NiPr2) [R2POCNiPr2-H; R = iPr (1a), R = tBu (1b)] and corresponding palladium complexes {2-(R2PO)-C6H3-6-(CH2NiPr2)}PdCl [(R2POCNiPr2)PdCl; R = iPr (2a), R = tBu (2b)] were synthesized in good yields. Treatment of palladium complex 2a with KI and AgOAc afforded the complexes (iPr2POCNiPr2)PdI (3a) and (iPr2POCNiPr2)Pd(OAc) (4a), respectively. Similarly, the reaction of 2a with benzothiazolyl-lithium produces the (iPr2POCNiPr2)Pd(benzothiazolyl) (5a) complex in a quantitative yield. The pincer palladium complex 2a efficiently catalyzes the C-H bond arylation of benzothiazole, substituted-benzoxazoles and 5-aryl oxazoles with diverse aryl iodides in the presence of CuI as a co-catalyst under mild reaction conditions. This represents the first example of a pincer palladium complex being applied for the direct C-H bond arylation of any heterocycle with low catalyst loading. A preliminary mechanistic investigation reveals that palladium nanoparticles are presumably not the catalytically active form of 2a and supports the direct involvement of the catalyst 2a, with complex 5a being a probable key intermediate in the catalytic reaction. This journal is
- Khake, Shrikant M.,Soni, Vineeta,Gonnade, Rajesh G.,Punji, Benudhar
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p. 16084 - 16096
(2014/12/11)
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- Iron catalyzed efficient synthesis of 2-arylbenzothiazoles from benzothiazole and olefins using environmentally benign molecular oxygen as oxidant
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A novel protocol for iron catalyzed arylation of benzothiazole with olefins has been developed using molecular oxygen as a greener oxidant. The reaction worked smoothly using inexpensive and easily available iron as a catalyst for the synthesis of 2-arylbenzothiazole derivatives in good to excellent yields.
- Khemnar, Ashok B.,Bhanage, Bhalchandra M.
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p. 8939 - 8942
(2014/03/21)
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- Copper-catalyzed double c-s bonds formation via different paths: Synthesis of benzothiazoles from n -benzyl-2-iodoaniline and potassium sulfide
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A new, highly efficient procedure for the synthesis of benzothiazoles from easily available N-benzyl-2-iodoaniline and potassium sulfide has been developed. The results show copper-catalyzed double C-S bond formation via a traditional cross-coupling reaction and an oxidative cross-coupling reaction.
- Zhang, Xiaoyun,Zeng, Weilan,Yang, Yuan,Huang, Hui,Liang, Yun
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supporting information
p. 876 - 879
(2014/03/21)
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