- A chromatography-free and aqueous waste-free process for thioamide preparation with Lawesson's reagent
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After completing the thio-substitution with Lawesson's reagent, ethanol was found to be effective in the decomposition of the inherent stoichiometric six-membered-ring byproduct from the Lawesson's reagent to a highly polarized diethyl thiophosphonate. The treatment significantly simplified the following chromatography purification of the desired thioamide in a small scale preparation. As scaling up the preparation of two pincer-type thioamides, we have successfully developed a convenient process with ethylene glycol to replace ethanol during the workup, including a traditional phase separation, extraction, and recrystallization. The newly developed chromatography-free procedure did not generate P-containing aqueous waste, and only organic effluents were discharged. It is believed that the optimized procedure offers the great opportunity of applying the Lawesson's reagent for various thio-substitution reactions on a large scale.
- Wu, Ke,Ling, Yichen,Ding, An,Jin, Liqun,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Hu, Xinquan
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p. 805 - 812
(2021/05/03)
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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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- 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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- Transition metal-free α-Csp3-H oxidative sulfuration of benzyl thiosulfates with anilines to form N-aryl thioamides
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A metal-free approach to N-aryl thioamides from Bunte salts and anilines in DMSO has been developed. This method tolerated a wide range of functional groups on the aromatic ring, providing an ideal way to N-aryl thioamides in good to excellent yields from cheap and easily available starting materials. A plausible mechanism was also proposed based on the X-ray single crystal diffraction, NMR and MS analyses of DMSO-concerning intermediates.
- Qiao, Mengjun,Zhang, Jinli,Chen, Ling,Zhou, Fengyi,Zhang, Yali,Zhou, Lingfei,Wu, Yangjie
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supporting information
p. 3790 - 3796
(2019/04/17)
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- Sulfur-Catalyzed Oxidative Coupling of Dibenzyl Disulfides with Amines: Access to Thioamides and Aza Heterocycles
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In the presence of catalytic amounts of elemental sulfur, dibenzyl disulfide/DMSO was found to be an excellent thiobenzoylating agent of amines to provide a wide range of thioamides. The reaction becomes autocatalytic when anilines substituted by an o-cyclizable group were used as nucleophile, leading to the corresponding 2-aryl aza heterocycles. (Figure presented.).
- Nguyen, Thanh Binh,Nguyen, Le Phuong Anh,Nguyen, Thi Thu Tram
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supporting information
p. 1787 - 1791
(2019/02/26)
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- Organocatalytic, difluorocarbene-based S-difluoromethylation of thiocarbonyl compounds
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Upon treatment with trimethylsilyl 2,2-difluoro-2-fluorosulfonylacetate (TFDA) and a catalytic amount of N,N,N′,N′-tetramethyl-1,8-diaminonaphthalene, secondary thioamides and thiocarbamates undergo selective difluoromethylation on the sulfur atom to give S-difluoromethyl thioimidates and thioiminocarbonates in good yields, respectively. This is the first report on the synthesis of acyclic difluoromethyl thioimidates and thioiminocarbonates. The key for S-difluoromethylation is the organocatalytic generation of difluorocarbene (:CF2) under mild conditions, which prevents decomposition of the substrates. This process provides an efficient approach to pharmaceuticals and agrochemicals bearing a difluoromethylsulfanyl group, starting from widely available thiocarbonyl compounds.
- Fuchibe, Kohei,Bando, Masaki,Takayama, Ryo,Ichikawa, Junji
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p. 133 - 138
(2015/03/04)
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- Decomposition of benzoylthioureas into benzamides and thiobenzamides under solvent-free conditions using iodine-alumina as the catalyst and its mechanistic study by density functional theory
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The breaking down of benzoylthioureas to benzamides and thiobenzamides in a single route using iodine-alumina as the catalyst under solvent-free conditions is highlighted. Results show that when an electron donating group, such as the methyl or methoxy group, is at the para-position of the aryl group of 1, benzamide (2) is the favoured product. When an electron withdrawing group, such as the chlorine or nitro group, is at the para-position of the aryl group of 1, thiobenzamide (3) is the favoured product. From the study of the reaction mechanism, it may be postulated that the formation of benzamide is due to the migration of the aryl group, whereas the formation of thiobenzamide may be due to the migration of the phenyl group. Thus, a new method for the formation of benzamides and thiobenzamides was developed.
- Nahakpam, Lokendrajit,Chipem, Francis A. S.,Chingakham, Brajakishor S.,Laitonjam, Warjeet S.
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supporting information
p. 2240 - 2247
(2015/03/18)
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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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- Nano n -propylsulfonated magnetic γ-Fe2O3 as an efficient and reusable catalyst for the synthesis of thioamides
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One-pot three-component reactions of aldehydes, amines, and sulfur are carried out in the presence of nano n-propylsulfonated magnetic γ-Fe2O3 as a catalyst for the synthesis of biologically interesting thioamide derivatives. The value of this catalytic method lies in its mild reaction catalyst and conditions, good yields, and ease of handling.
- Yin, Zhikui,Zheng, Bin
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p. 527 - 531
(2013/10/21)
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- Sulfonic acid functionalized nano Γ-Al 2O 3: A new, efficient, and reusable catalyst for synthesis of thioamides
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Sulfonic acid functionalized nano γ-Al2O3 is easily prepared by the reaction of nano γ-Al2O3 with 1,3-propane sulfone. This reagent can be used as an eficient catalyst for the synthesis of thioamides. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be recovered for several times.
- Yin, Zhikui,Zheng, Bin,Ai, Fang
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p. 1412 - 1420
(2013/10/08)
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- Synthesis of thioamides by catalyst-free three-component reactions in water
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Three-component reactions involving amines, aldehydes, and elemental sulfur powder are reported to afford thioamides in a simple one-pot procedure in the absence of a catalyst. A variety of thioamides can be obtained in good to excellent yields up to 88 %. Three-component reactions involving amines, aldehydes, and sulfur powder afford thioamides in a simple one-pot procedure. A variety of substituted thioamides are obtained in good to excellent yields up to 88 %. Copyright
- Xu, Hualong,Deng, Hang,Li, Zhengkai,Xiang, Haifeng,Zhou, Xiangge
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supporting information
p. 7054 - 7057
(2013/11/06)
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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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supporting information; experimental part
p. 1678 - 1682
(2012/07/17)
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- Sulfated tungstate: An efficient catalyst for synthesis of thioamides via Kindler reaction
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New application of sulfated tungstate, a mildly acidic solid inorganic acid, as reusable heterogeneous catalyst for efficient Kindler reaction, a three component reactions of aldehydes, amines and sulfur, for synthesis of thioamides is discussed.
- Pathare, Sagar P.,Chaudhari, Pramod S.,Akamanchi, Krishnacharya G.
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experimental part
p. 125 - 129
(2012/07/03)
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- Palladium-catalyzed synthesis of 2-substituted benzothiazoles via a C-H functionalization/intramolecular C-S bond formation process
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(Chemical Equation Presented) Catalytic synthesis of 2-substituted benzothiazoles from thiobenzanilides was achieved in the presence of a palladium catalyst through C-H functionalization/C-S bond formation. This method features the use of a novel catalytic system consisting of 10 mol % of Pd(II), 50 mol % of Cu(I), and 2 equiv of Bu4NBr that produced variously substituted benzothiazoles in high yields with good functional group tolerance.
- Inamoto, Kiyofumi,Hasegawa, Chisa,Hiroya, Kou,Doi, Takayuki
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supporting information; experimental part
p. 5147 - 5150
(2009/05/30)
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- Facile preparation of amides from thioamides by ceric ammonium nitrate
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Ceric ammonium nitrate (CAN) is found to be a good oxidizing agent which converts thioamides into their oxygen analogues in aqueous acetic acid under very mild conditions.
- Movassagh, Barahman,Meibodi, Forhatosadat,Sobhani, Shahin
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p. 1296 - 1298
(2007/10/03)
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- Kinetics and mechanism of the aminolysis of phenyl dithiobenzoates
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The kinetics and mechanism of the reactions of phenyl dithiobenzoates with anilines in acetonitrile at 55.0 deg C have been studied.The large magnitude of βx(βnuc) and the signs of cross-interaction constants, ρeXY > 0, ρYZ XZ > 0, are all consistent with the carbonyl addition mechanism in which the breakdown of the tetrahedral intermediate, T+/-, is rate limiting.The thiocarbonyl group (C=S) is found to favour amine expulsion in contrast to the carbonyl group (C=O) which favours the S-bonded nucleofuge expulsion from T+/-.The signs of cross-interaction constants, ρXY, ρYZ and/or ρXZ, are shown to provide useful mechanistic criteria for distinguishing, especially, the carbonyl addition mechanism involving the rate-limiting breakdown of the tetrahedral intermediate (T+/- from the concerted SN2 mechanism.
- Oh, Hyuck Keun,Shin, Chul Ho,Lee, Ikchoon
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p. 1169 - 1174
(2007/10/02)
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- ANTIMYCOBACTERIAL THIOBENZANILIDES
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A group of 30 thiobenzanilides active against Mycobacterium kansasii have been synthesized and their 1H NMR and UV spectra and RM values (TLC on silica gel impregnated with methylsilicone oil) have been measured.From the correlation between the chemical shifts of the thioamide proton in the 1H NMR spectra and the Hammett constants it can be concluded that the substituents in both aromatic rings uniformly affect the electron density of the thioamide group.The antimycobacterial activity is probably connected with local molecular parameters and can be considered to be approximately additive with respect to both parts of the molecule.
- Waisser, Karel,Houngbedji, Nestor,Machacek, Milos,Sekera, Miroslav,Urban, Josef,Odlerova, Zelmira
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p. 307 - 316
(2007/10/02)
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- Reaction of N,N-Dimethyl-N'-thiobenzoylformamidine and N,N-Dimethyl-N'-phenylthiocarbamoylformamidine with N-Arylbenzimidoyl Chlorides
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The reactions of N,N-dimethyl-N'-thiobenzoylformamidine (1) and N,N-dimethyl-N'-phenylthiocarbamoylformamidine (4) with N-arylbenzimidoyl chlorides (2) have been studied.Compound 1 reacts with 2 in dry chloroform at room temperature to give dimidoyl sulphides (3) in good yields.However, the reaction of 2 with 4 in dry tetrahydrofuran under reflux results in the formation of a mixture of thiobenzanilides (5) and N-aryl-N'-phenylbenzamidines (6).Possible mechanistic pathways for these reactions have been suggested.
- Baruah, P. D.,Roy, G.,Satsangi, R.,Mahajan, M. P.
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p. 357 - 359
(2007/10/02)
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