- 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 0049-0051
(2021/06/22)
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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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- TBHP/KI-Promoted Annulation of Anilines, Ethers, and Elemental Sulfur: Access to 2-Aryl-, 2-Heteroaryl-, or 2-Alkyl-Substituted Benzothiazoles
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An efficient TBHP/KI-promoted annulation of anilines with ethers and elemental sulfur has been developed through the selective C-O bond cleavage of ethers under transition-metal-free conditions. A wide range of 2-aryl-, 2-heteroaryl-, and 2-alkyl-substituted benzothiazoles were easily prepared with satisfactory yields and good functional group compatibility.
- Zhang, Jie,Zhao, Xin,Liu, Ping,Sun, Peipei
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p. 12596 - 12605
(2019/10/11)
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- Efficient 2-aryl benzothiazole formation from acetophenones, anilines, and elemental sulfur by iodine-catalyzed oxidative C(CO)-C(alkyl) bond cleavage
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A novel and efficient iodine-catalyzed one-pot reaction of aromatic amines, acetophenones, and elemental sulfur for the synthesis of 2-aryl benzothiazoles is described. The process involves sequential C?S and C-N bond formation followed by C(CO)?C bond cleavage from readily accessible starting materials. A wide range of functional groups is tolerated under oxidant and metal-free condition and moderate to good product yields are obtained.
- Liu, Yafeng,Yuan, Xinglong,Guo, Xin,Zhang, Xueguo,Chen, Baohua
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p. 6057 - 6062
(2018/09/11)
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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 0045; 0056
(2018/05/16)
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- Electrochemical intramolecular dehydrogenative C-S bond formation for the synthesis of benzothiazoles
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An external oxidant-free intramolecular dehydrogenative C-S cross-coupling has been developed under undivided electrolytic conditions. Various 2-aminobenzothiazoles could be synthesized with up to 99% yield from the direct combination of aryl isothiocyanates with amines. In the presence of a base, this reaction protocol is also applicable for the synthesis of benzothiazoles from N-aryl thioamides.
- Wang, Pan,Tang, Shan,Lei, Aiwen
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supporting information
p. 2092 - 2095
(2017/07/24)
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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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- Preparation method of 2-arylbenzothiazole compound
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The invention relates to a preparation method of a 2-arylbenzothiazole compound. The method comprises the steps that a benzothiazole compound, diaryliodonium salt, a catalyst, a phosphine ligand and alkali are added into an organic solvent, reacting is conducted for 20-36 hours at the temperature of 60 DEG C to 100 DEG C, and after complete reacting is achieved, reaction liquid is obtained; after the reaction liquid is sequentially subjected to conventional extraction, drying, concentration and column chromatography separation, the compound is obtained. The preparation method belongs to a two-component one-pot reaction, the conditions are mild, the raw materials are easy to prepare and obtain, operation is easy, the yield is high, green environmental protection and economic conservation are achieved, large-scale production can be achieved, and the good application potential on medicine, pesticides, organic synthesis and materials and the good industrial application prospect are achieved.
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Paragraph 0014; 0038; 0039; 0040
(2017/03/25)
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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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- External Oxidant-Free Oxidative Cross-Coupling: A Photoredox Cobalt-Catalyzed Aromatic C-H Thiolation for Constructing C-S Bonds
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An external oxidant-free oxidative coupling for aromatic C-H thiolation by visible-light photoredox cobalt-catalysis has been developed. Various substrates could afford benzothiazoles in good to excellent yields, and only H2 is generated as a side product. When catalytic TBAOH was used as the base, not only 2-aryl but also 2-alkylbenzothiazoles could be obtained through this novel dehydrogenative coupling reaction. This method could be scaled up and applied to the synthesis of biologically active molecules bearing benzothiazole structural scaffolds (potent antitumor agents). Furthermore, the unexpected oxidation byproduct amides, which are often generated in oxidative cyclization of thiobenzanilides, can be completely avoided. Mechanistic studies showed that the H2 originates from the substrates. The kinetic studies indicate that the interaction between the cobalt catalyst and proton might be involved in the rate-limiting process. (Chemical Equation Presented).
- Zhang, Guoting,Liu, Chao,Yi, Hong,Meng, Qingyuan,Bian, Changliang,Chen, Hong,Jian, Jing-Xin,Wu, Li-Zhu,Lei, Aiwen
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supporting information
p. 9273 - 9280
(2015/08/11)
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- Organocatalytic syntheses of benzoxazoles and benzothiazoles using aryl iodide and oxone via C-H functionalization and C-O/S bond formation
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An organocatalytic protocol for the syntheses of 2-substituted benzoxazoles and benzothiazoles is described from alkyl-/arylanilides and alkyl-/arylthioanilides using 1-iodo-4-nitrobenzene as catalyst and oxone as an inexpensive and environmentally safe terminal oxidant at room temperature in air via oxidative C-H functionalization and C-O/S bond formation. The procedure is simple and general and provides an effective route for the construction of functionalized 2-alkyl-/arylbenzoxazoles and 2-alkyl-/arylbenzothiazoles with moderate to high yields. The synthetic and mechanistic aspects have been described.
- Alla, Santhosh Kumar,Sadhu, Pradeep,Punniyamurthy, Tharmalingam
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p. 7502 - 7511
(2014/09/16)
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- Palladium-catalyzed C-H cyclization in water: A milder route to 2-arylbenzothiazoles
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Water was successfully employed as a reaction medium in palladium-catalyzed C-H cyclization of thiobenzanilides. Reactions efficiently proceeded under considerably mild conditions such as 40 °C in water, providing a more practical, greener method for the synthesis of 2-arylbenzothiazoles. For some substrates, the addition of an amphiphilic surfactant greatly enhanced the process. The method represents a rare example of palladium-catalyzed C-H functionalization processes performed in water. Georg Thieme Verlag Stuttgart · New York.
- Inamoto, Kiyofumi,Nozawa, Kanako,Kondo, Yoshinori
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scheme or table
p. 1678 - 1682
(2012/07/17)
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- Fe-catalysed oxidative C-H functionalization/C-S bond formation
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Iron was used as the catalyst for the direct C-H functionalization/C-S bond formation under mild conditions. Various substrates could afford benzothiazoles in moderate to excellent yields. Preliminary mechanistic studies revealed that pyridine played a crucial role for the high yields and selectivities.
- Wang, Haibo,Wang, Lu,Shang, Jinsai,Li, Xing,Wang, Haoyuan,Gui, Jie,Lei, Aiwen
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supporting information; experimental part
p. 76 - 78
(2012/01/05)
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- Efficient 2-aryl benzothiazole formation from aryl ketones and 2-aminobenzenethiols under metal-free conditions
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2-Aryl benzothiazole formation from aryl ketones and 2-aminobenzenethiols under metal- and I2-free conditions was described. Various 2-aryl benzothiazoles were selectively obtained in good yields using molecular oxygen as oxidant. DMSO played an important role in this transformation. Functional groups such as methyl, methoxy, fluoro, chloro, bromo and nitro groups were tolerated under the optimized reaction conditions.
- Liao, Yunfeng,Qi, Hongrui,Chen, Shanping,Jiang, Pengcheng,Zhou, Wang,Deng, Guo-Jun
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supporting information
p. 6004 - 6007
(2013/02/22)
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- Use of molecular oxygen as a reoxidant in the synthesis of 2-substituted benzothiazoles via palladium-catalyzed C-H functionalization/intramolecular C-S bond formation
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Molecular oxygen (O2) was successfully employed as a reoxidant in cyclizations of thiobenzanilides 1a-s through a palladium-catalyzed C-H functionalization/intramolecular C-S bond formation process, leading to an efficient, green method for the synthesis of 2-arylbenzothiazoles 2a-s. Addition of cesium fluoride (CsF) greatly enhanced the reactions, which produced variously substituted 2-arylbenzothiazoles with good functional group tolerance. Thioureas 4a-j were also found to be suitable substrates for the cyclization process using a palladium/O2 catalyst system, thus generating 2-aminobenzothiazoles 5a-j. One-pot syntheses of 2-aminobenzothiazoles 5a-j from aryl isothiocyanates 6 and amines 7 were also successful.
- Inamoto, Kiyofumi,Hasegawa, Chisa,Kawasaki, Junpei,Hiroya, Kou,Doi, Takayuki
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experimental part
p. 2643 - 2655
(2010/12/25)
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- Conversion of thiobenzamides to benzothiazoles via intramolecular cyclization of the aryl radical cation
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A new and general method has been developed for the intramolecular cyclization of thiobenzamides to benzothiazoles via aryl radical cations as reactive intermediates. The method utilizes phenyliodine(III) bis(trifluoroacetate) (PIFA) in trifluoroethanol or cerium ammonium nitrate (CAN) in aqueous acetonitrile at room temperature to effect cyclization within 30 min in moderate yields.
- Downer-Riley, Nadale K.,Jackson, Yvette A.
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p. 7741 - 7744
(2008/12/20)
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