- Disubstituted Ferrocenyl Iodo- And Chalcogenoalkynes as Chiral Halogen and Chalcogen Bond Donors
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Asymmetric catalysis based on halogen and chalcogen bonds (XB and ChB) is in its infancy, and the search for new chiral XB and ChB donors represents a crucial step toward its development. In this context, we designed and prepared new motifs containing three key substructures: namely, regions of electron charge density depletion centered on iodine and chalcogen atoms, the ethynyl functionality, and the planar chiral ferrocenyl platform. Nine ferrocenyl iodoalkynes were prepared as pure enantiomers by asymmetric synthesis. The XB donor property of racemic ferrocenyl iodoalkynes was demonstrated in solution in two benchmark reactions: the Ritter reaction and the benzoxazole synthesis from thioamides. In contrast, the ferrocenyl chalcogenoalkynes were far less active in these reactions. The potential of racemic and enantiopure ferrocenyl iodoalkynes as XB donors was also confirmed by X-ray diffraction analysis, showing I···C contacts between the electropositive σ-hole of the iodine atom and electron-rich πclouds for all crystal structures studied in the solid state.
- Aubert, Emmanuel,Cossu, Sergio,Mamane, Victor,Pale, Patrick,Peluso, Paola,Weiss, Robin,Wenger, Emmanuel
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- A case of competitive demethylation by boron tribromide-methyl sulfide complex. A new route to oxazoloquinolines
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Reaction of boron tribromide-methyl sulfide complex with 6-methoxy-5- amidoquinolines provides oxazolo(4,5-f) quinolines. In contrast under similar conditions boron tribromide gives only 6-hydroxy-5-amidoquinolines.
- Beviere, Corinne,Rocher, Richard,Chenault, Jacques
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Read Online
- Acid-promoted cleavage of the C–C double bond of N-(2-Hydroxylphenyl)enaminones for the synthesis of benzoxazoles
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An acid-mediated selective cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminones with formation a new C–O bond for the synthesis of 2-substituted benzoxazoles has been developed. This protocol proceeds under transition metal- and oxidant-free conditions with broad functional group tolerance. The oxidative cleavage of C–C double bond of N-(2-hydroxylphenyl)enaminone is also realized using NCS or NFSI as oxidants with release of 2,2-dihalogen-acetophenone fragments.
- Ge, Bailu,Peng, Yanling,Liu, Jing,Wen, Si,Peng, Cheng,Cheng, Guolin
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- Reusable Palladium Nanoparticles Catalyzed Oxime Ether Directed Mono Ortho-Hydroxylation under Phosphine Free Neutral Condition
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An efficient, reusable and stable binaphthyl stabilized Pd-nanoparticles (Pd-BNP) catalyzed the direct ortho-C?H hydroxylation of acetophenone oxime ethers under neutral and phosphine ligand-free condition has been developed. A readily available, economic, safe and greener oxidant oxone has been used in this direct ortho-hydroxylation. The scope of the reaction has been studied with various acetophenone oxime ethers including electron rich to electron deficient system and the reaction afforded only mono hydroxylated products in a highly regioselective manner. Several control experiment results confirmed that the oxone is the hydroxyl source. The Pd-BNP catalyst has been reused up to five times. The heterogeneous test confirmed that the reaction is catalyzed by the heterogeneous Pd-BNP catalyst. (Figure presented.).
- Saha, Rajib,Perveen, Naziya,Nihesh, Naorem,Sekar, Govindasamy
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supporting information
p. 510 - 519
(2018/12/11)
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- Method for synthesizing benzoxazole through microwave radiation of benzamide compound in water phase
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The invention discloses a method for synthesizing benzoxazole through microwave radiation of a benzamide compound in a water phase. The benzamide compound is added into the water phase under the microwave condition to be subjected to a cyclization reaction for generating the benzoxazole under the alkali condition, and the method for preparing the benzoxazole is environmentally friendly, easy and convenient to operate, safe, low in cost and efficient. Compared with the prior art, the method can be applied to a large number of functional groups, the yield is high, the number of by-products is small, and the method is easy to operate, safe, low in cost and environmentally friendly. (Please see the specifications for the formula).
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Paragraph 0014
(2019/03/08)
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- A 2 - substituted benzoxazole derivative of the preparation method
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The invention discloses a 2 - substituted benzoxazole derivative of the preparation method, its reaction as follows: . The present invention can be 2 - substituted pyrrole derivatives, acetophenone derivatives can be obtained and at the same time 2, 2 - dihalo acetophenone derivatives; and through the C (sp2 ) - C (sp2 ) At the same time selectively fracture of the aromatization. The method of the invention the resulting raw materials are easy, high yield, mild reaction conditions, the reaction time is short, wide substrate range, reaction specificity is strong, easy post treatment and green environmental protection.
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Paragraph 0070-0073
(2019/07/04)
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- Palladium-Catalyzed Methylation of Aryl, Heteroaryl, and Vinyl Boronate Esters
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A method for the direct methylation of aryl, heteroaryl, and vinyl boronate esters is reported, involving the reaction of iodomethane with aryl-, heteroaryl-, and vinylboronate esters catalyzed by palladium and PtBu2Me. This transformation occurs with a remarkably broad scope and is suitable for late-stage derivatization of biologically active compounds via the boronate esters. The unique capabilities of this method are demonstrated by combining carbon-boron bond-forming reactions with palladium-catalyzed methylation in a tandem transformation.
- Haydl, Alexander M.,Hartwig, John F.
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supporting information
p. 1337 - 1341
(2019/02/26)
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- Eco-friendly syntheses of 2-substituted benzoxazoles and 2-substituted benzothiazoles from 2-aminophenols, 2-aminothiophenols and DMF derivatives in the presence of imidazolium chloride
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A simple, economical and metal-free approach to the synthesis of 2-substituted benzoxazoles and 2-substituted benzothiazoles from 2-aminophenols, 2-aminothiophenols and DMF derivatives, only using imidazolium chloride (50% mmol) as promoter without any other additive, was reported. Various 2-substituted benzoxazoles and 2-substituted benzothiazoles were thus prepared in moderate to excellent yields.
- Tian, Qingqiang,Luo, Wen,Gan, Zongjie,Li, Dan,Dai, Zeshu,Wang, Huajun,Wang, Xuetong,Yuan, Jianyong
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supporting information
(2019/01/21)
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- Synthesis method of 2-substituted benzoxazole, 2-substituted benzothiazole and derivatives thereof
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The invention provides a synthesis method of 2-substituted benzoxazole, 2-substituted benzothiazole and derivatives thereof. In the method, through ortho-aminophenol/2-aminothiophenol cyclization catalyzed by imidazole hydrochloride, synthesis of functionalized 2-substituted benzoxazole and 2-substituted benzothiazole is realized; the method is simple, economical and high in practicality. No othercatalysts or additives are used, the synthesis method ensures good functional group tolerance and excellent yield and purity, the reaction time is short, no harsh reaction conditions are needed, andthe method is suitable for industrial production.
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Paragraph 0040; 0052-0053
(2019/02/10)
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- Metal free montmorillonite KSF clay catalyzed practical synthesis of benzoxazoles and benzothiazoles under aerobic conditions
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An efficient method for the synthesis of benzoxazoles and benzothiazoles via montmorillonite KSF clay catalyzed condensation reaction between 2-aminophenols or 2-aminothiophenols and β-diketones is reported. The efficiency of the reaction reflects from the wide substrate scope with electronic differentiation on aryls. The reaction is metal free and proceeds without the exclusion of air or moisture, and further the catalyst can be recycled up to 3–5 catalytic cycles.
- Kummari, Vijaya Babu,Chiranjeevi, Kalavakuntla,Suman Kumar, Alleni,Kumar, Rathod Aravind,Yadav, Jhillu Singh
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supporting information
p. 3335 - 3342
(2019/11/11)
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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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- Sodium dichloroiodate promoted C-C bond cleavage: An efficient synthesis of 1,3-Benzazoles via condensation of o -amino/mercaptan/hydroxyanilines with β -diketones
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An efficient aqueous sodium dichloroiodate (NaICl 2) mediated protocol is developed for the synthesis of benzofused azoles by the cyclization of 2-amino anilines/thiophenols/phenols with β-diketone compounds. The reactions gave moderate to good yield of the corresponding 2-substituted benzimidazoles/benzothiazoles/benzoxazoles under mild conditions. This tandem process involved a C-C bond cleavage and C-N bond formation. Graphical Abstract?: SYNOPSIS A facile and single protocol for the synthesis of three versatile 1,3-benzazoles viz 2-substituted 1H-benzimidazoles, benzoxazoles and benzothiazoles from readily available starting materials, 1,3-diketones and corresponding o-amino anilines/thiophenols/phenols, by aqueous sodium dichloroiodate (NaICl 2) mediated C—C bond cleavage has been developed. The reaction provides a rapid access to these 1, 3-benzazoles in good yields, thus speeding up the drug discovery process.[Figure not available: see fulltext.].
- Bhagat, Saket B,Ghodse, Shrikant M,Telvekar, Vikas N
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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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- Direct Detection of the Open-Shell Singlet Phenyloxenium Ion: An Atom-Centered Diradical Reacts as an Electrophile
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A new photoprecursor to the phenyloxenium ion, 4-methoxyphenoxypyridinium tetrafluoroborate, was investigated using trapping studies, product analysis, computational investigations, and laser flash photolysis experiments ranging from the femtosecond to the millisecond time scale. These experiments allowed us to trace the complete arc of the photophysics and photochemistry of this photoprecursor beginning with the initially populated excited states to its sequential formation of transient intermediates and ultimate formation of stable photoproducts. We find that the excited state of the photoprecursor undergoes heterolysis to generate the phenyloxenium ion in ～2 ps but surprisingly generates the ion in its open-shell singlet diradical configuration (1A2), permitting an unexpected look at the reactivity of an atom-centered open-shell singlet diradical. The open-shell phenyloxenium ion (1A2) has a much shorter lifetime (τ ～ 0.2 ns) in acetonitrile than the previously observed closed-shell singlet (1A1) phenyloxenium ion (τ ～ 5 ns). Remarkably, despite possessing no empty valence orbitals, this open-shell singlet oxenium ion behaves as an even more powerful electrophile than the closed-shell singlet oxenium ion, undergoing solvent trapping by weakly nucleophilic solvents such as water and acetonitrile or externally added nucleophiles (e.g., azide) rather than engaging in typical diradical chemistry, such as H atom abstraction, which we have previously observed for a triplet oxenium ion. In acetonitrile, the open-shell singlet oxenium ion is trapped to generate ortho and para Ritter intermediates, one of which (para) is directly observed as a longer-lived species (τ ～ 0.1 ms) in time-resolved resonance Raman experiments. The Ritter intermediates are ultimately trapped by either the 4-methoxypyridine leaving group (in the case of para addition) or trapped internally via an essentially barrierless rearrangement (in the case of ortho addition) to generate a cyclized product. The expectation that singlet diradicals react similarly to triplet or uncoupled diradicals needs to be reconsidered, as a recent study by Perrin and Reyes-Rodríguez (J. Am. Chem. Soc. 2014, 136, 15263) suggested the unsettling possibility that singlet p-benzyne could suffer nucleophilic attack to generate a naked phenyl anion. Now, this study provides direct spectroscopic observation of this phenomenon, with an atom-centered open-shell singlet diradical reacting as a powerful electrophile. To the question of whether a nucleophile can attack a singly occupied molecular orbital, the answer is apparently yes, at least if another partially occupied orbital is available to avoid violation of the rules of valence.
- Du, Lili,Qiu, Yunfan,Lan, Xin,Zhu, Ruixue,Phillips, David Lee,Li, Ming-De,Dutton, Andrew S.,Winter, Arthur H.
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p. 15054 - 15059
(2017/11/03)
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- 2-substituted benzoxazole preparation method of compound
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The invention relates to a preparing method of 2-substituted benzoxazole compounds. The compounds are obtained by reaction of products obtained by reaction of acyl chloride and o-nitrophenol or derivatives thereof under catalyzing of reducing agent ammonium formate, a solvent and palladium-containing agents. According to the method, the reaction condition is mild, environment is protected, raw materials are rich and easy to obtain, operation is easy, yield is high, and various kinds of performance are optimized.
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- Copper-catalyzed synthesis of benzoxazoles: Via tandem cyclization of 2-halophenols with amidines
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This work reports a simple, efficient and alternative synthetic route for the preparation of benzoxazoles via tandem cyclization of 2-halophenols with amidines. The developed methodology is free from ligands and uses inexpensive and easily available CuCl as a catalyst. This protocol avoids the use of any oxidant or inorganic acids. Various benzoxazole derivatives were synthesized in good to excellent yields. To the best of our knowledge, this is the first time that the synthesis of benzoxazoles from 2-halophenols with both aromatic and aliphatic amidines is reported. Owing to the simplicity of this protocol, the preparation of benzoxazoles could be achieved at a gram scale level.
- Tiwari, Abhishek R.,Bhanage, Bhalchandra M.
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p. 7920 - 7926
(2016/08/30)
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- Iodoalkyne-Based Catalyst-Mediated Activation of Thioamides through Halogen Bonding
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Halogen bonding catalysis has recently gained increasing attention as a powerful tool to activate organic molecules. However, the variety of the catalyst structure has been quite limited so far. Herein, we report the first example of the use of an iodoalkyne as a halogen bond donor catalyst. By using an iodoalkyne bearing a pentafluorophenyl group as a catalyst, thioamides were efficiently activated and reacted with 2-aminophenol to generate benzoxazoles in good yield. Mechanistic studies, including 13C NMR spectroscopic analysis and several control experiments, provided concrete evidence that this catalytic activation is based on halogen bonding. Thus, the results obtained in this study demonstrate that iodoalkynes can serve as a new scaffold for future development of halogen bonding catalysis.
- Matsuzawa, Akinobu,Takeuchi, Shiho,Sugita, Kazuyuki
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supporting information
p. 2863 - 2866
(2016/10/25)
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- Cu-Pd/γ-Al2O3 catalyzed the coupling of multi-step reactions: Direct synthesis of benzimidazole derivatives
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The coupling of multi-step reactions catalyzed by a heterogeneous catalyst is an important path to accomplish some unconventional chemical transformations. Since the starting materials generated from previous steps were adsorbed on the catalyst, the activation energy of following steps was largely decreased, and thus the reaction conditions were more mild and environmental friendly. Catalyzed by a multifunctional Cu-Pd/γ-Al2O3 catalyst, the transfer hydrogenation and successive cyclization coupling reaction from o-nitroaniline and alcohol to afford benzimidazole derivatives in high yield was realized. The catalyst could be reused several times without loss of activity. The synergies of reforming hydrogenation of Cu-Pd bimetal and support acidity of γ-Al2O3 were responsible for this catalytic transformation.
- Feng, Feng,Ye, Jia,Cheng, Zheng,Xu, Xiaoliang,Zhang, Qunfeng,Ma, Lei,Lu, Chunshan,Li, Xiaonian
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p. 72750 - 72755
(2016/08/09)
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- Silylated derivatives of N-(2-hydroxyphenyl)acetamide: Synthesis and structure
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The N-(2-(trimethylsilyloxy)phenyl)acetamide 1 was synthesized via reaction of N-(2-hydroxyphenyl)acetamide with chlorotrimethylsilane. Transsilylation of new compound 1 by chloro(chloromethyl)dimethylsilane leads to 4-acetyl-2,2-dimethyl-3,4-dihydro-2H-1,4,2-benzoxazasiline 3. The structures of the new compounds were investigated by 1H, 13C and 29Si NMR spectroscopy, X-ray single-crystal analysis, FTIR spectroscopy and DFT methods.
- Nikonov, Alexey Yu.,Sterkhova, Irina V.,Lazarev, Igor M.,Albanov, Alexander I.,Lazareva, Natalya F.
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- Ligand-promoted, copper nanoparticles catalyzed one-pot synthesis of substituted benzoxazoles from 2-bromoanilines and acyl chlorides
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A facile, highly efficient, and practical one-pot synthetic strategy for benzoxazoles was developed by using copper nanoparticles as a catalyst with o-bromoanilines and acyl chlorides as starting materials. With the promotion of 1,10-phenanthroline ligand, the copper nanoparticles catalyst showed highly catalytic activity under mild conditions. This methodology is tolerant of a wide variety of functional groups and gives good to excellent yields in most examples. Furthermore, the solid catalyst could be recovered and reused conveniently several times with satisfactory yields.
- Wang, Yong,Wu, Chaolong,Nie, Shoujie,Xu, Dingjian,Yu, Min,Yao, Xiaoquan
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supporting information
p. 6827 - 6832
(2015/11/27)
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- Acid Catalyzed Direct-Amidation-Dehydrocyclization of 2-Hydroxy-acetophenones to Benzoxazoles by a One-Pot Sustainable Synthesis
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A series of 2-methyl-benzoxazoles have been synthesized starting from 2-hydroxy-acetophenones via a one-pot three steps reaction. Hydroxylamonium salt has been used as amidation agent. The reaction occurs with different anions, but the best results is achieved with hydroxylamonium hydrchloride. Despite the number of consecutive stages, the reaction is highly selective. Mild reaction conditions and various solvents can be used, but trifluoroacetic acid is the preferred. Almost, complete recovery of the trifluoroacetic acid can be achieved by vacuum distillation. The role of trifluoroacetic acid, as well as, of the hydroxylamonium salt suggests a cooperative effect leading to high selective formation of 2-methyl-benzoxazoles. Graphical Abstract: One-pot TFA catalyzed synthesis of benzoxazoles starting from 2-hydroxyacetophenones. (Chemical Equation Presented).
- Rancan, Elia,Aric, Fabio,Quartarone, Giuseppe,Ronchin, Lucio,Vavasori, Andrea
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p. 939 - 946
(2015/08/06)
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- Utility of Nitrogen Extrusion of Azido Complexes for the Synthesis of Nitriles, Benzoxazoles, and Benzisoxazoles
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The utility of the nitrogen extrusion reaction of azido complexes, generated in situ from the corresponding aldehydes or ketones with TMSN3 in the presence of ZrCl4 or TfOH, has been described. These azido complexes could undergo three different pathways, depending on the substrates. First, azido methanolate complexes or imine diazonium ions could lead to benzisoxazole products via an intramolecular nucleophilic substitution. Second, imine diazonium ions could also undergo either the elimination of proton to provide nitrile products in good to excellent yields or an aryl migration, followed by an intramolecular nucleophilic addition, to give benzoxazole products in good yields.
- Nimnual, Phongprapan,Tummatorn, Jumreang,Thongsornkleeb, Charnsak,Ruchirawat, Somsak
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p. 8657 - 8667
(2015/09/15)
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- Ag@TiO2 nanocomposite; Synthesis, characterization and its application as a novel and recyclable catalyst for the one-pot synthesis of benzoxazole derivatives in aqueous media
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In the present study, we use a Ag@TiO2 nanocomposite for the efficient synthesis of benzoxazole derivatives via the one-pot condensation of 2-aminophenol and several aromatic aldehydes or orthoesters or carboxylic acids or amides or acyl chlorides in water at room temperature. In all situations the preferred products were synthesized with excellent yields. The short reaction times, high yields, safety and mild conditions, simplicity, non-toxicity and easy workup are the main merits of this protocol.
- Maleki, Behrooz,Baghayeri, Mehdi,Vahdat, Seyed Mohammad,Mohammadzadeh, Abbas,Akhoondi, Somaieh
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p. 46545 - 46551
(2015/06/16)
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- Benzimidazoles and benzoxazoles via the nucleophilic addition of anilines to nitroalkanes
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PPA-induced umpolung triggers efficient nucleophilic addition of unactivated anilines to nitroalkanes to produce N-hydroxyimidamides. The latter undergo sequential acid-promoted cyclocondensation with ortho-OH or ortho-NHR moieties to afford benzoxazoles
- Aksenov, Alexander V.,Smirnov, Alexander N.,Aksenov, Nicolai A.,Bijieva, Asiyat S.,Aksenova, Inna V.,Rubin, Michael
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p. 4289 - 4295
(2015/04/14)
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- Graphene oxide as a heterogeneous reagent promoted synthesis of 2-substituted 1,3-benzazoles in water
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An efficient chemical method for the synthesis of benzimidazoles, benzothiazoles, and benzoxazoles has been developed through the condensation of various aldehydes with o-phenylenediamine, o-aminothiophenol, and o-aminophenol using graphene oxide (GO) as an oxidant in water. These benzazoles are also prepared through a one-pot oxidation/condensation tandem process by reacting alcohols with 2-amino-(thio)phenol/aniline in the presence of GO in poly(ethylene glycol) as a safe media. Moreover, this carbonaceous material could be readily separated using a simple filtration.
- Khalili, Dariush,Banazadeh, Ali Reza
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p. 1693 - 1706
(2016/01/26)
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- Hypervalent iodine-mediated synthesis of benzoxazoles and benzimidazoles via an oxidative rearrangement
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A Beckmann-type rearrangement of o-hydroxy and o-aminoaryl N-H ketimines has been developed to prepare benzoxazoles and N-Ts benzimidazoles, respectively. The ketimine derivatives were easily prepared by condensation of ammonia with the corresponding ketones and (diacetoxyiodo)benzene was found to act as an efficient oxidant to trigger the [1,2]-aryl migration towards the formation of the desired heterocycles. Depending on the substitution pattern, the results revealed another mechanistic pathway through which benzisoxazoles or 1H-indazoles could be formed. The Beckmann-type rearrangement strategy was applied to the synthesis of benzimidazole-containing biorelevant targets such as chlormidazole and clemizole.
- Zhang, Xiaohui,Huang, Ruofeng,Marrot, Jér?me,Coeffard, Vincent,Xiong, Yan
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p. 700 - 708
(2015/02/02)
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- Facile synthesis of benzimidazole, benzoxazole, and benzothiazole derivatives catalyzed by sulfonated rice husk ash (RHA-SO3H) as an efficient solid acid catalyst
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A mild, simple, and efficient solvent-free method, with sulfonated rice husk ash as solid acid catalyst, has been developed for preparation of benzimidazole, benzoxazole, and benzothiazole derivatives. The products are obtained in good to high yields after very short reaction times, and the catalyst can be reused five times without loss of its catalytic activity.
- Shirini, Farhad,Mamaghani, Manouchehr,Seddighi, Mohadeseh
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p. 5611 - 5619
(2015/07/08)
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- DAST-promoted Beckmann rearrangement/intramolecular cyclization of acyclic ketoximes: Access to 2-oxazolines, benzimidazoles and benzoxazoles
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The first example of DAST-promoted Beckmann rearrangement/intramolecular cyclization of acyclic ketoximes is described. This unique protocol represents a direct and effective pathway to 2-oxazolines, benzimidazoles and benzoxazoles in moderate to good yields.
- Li, Huiqin,Qin, Jian,Yang, Zonglian,Guan, Xiaoxue,Zhang, Lin,Liao, Peiqiu,Li, Xingqi
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supporting information
p. 8637 - 8639
(2015/05/20)
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- Synthesis of benzoxazoles from 2-aminophenols and β-diketones using a combined catalyst of br?nsted acid and copper iodide
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Cyclization reactions of 2-aminophenols with β-diketones catalyzed by a combination of Br?nsted acid and CuI are presented. Various 2-substituted benzoxazoles were obtained through these reactions. Different substituents such as methyl, chloro, bromo, nitro, and methoxy on 2-aminophenol are tolerated under the optimized reaction conditions.
- Mayo, Muhammad Shareef,Yu, Xiaoqiang,Zhou, Xiaoyu,Feng, Xiujuan,Yamamoto, Yoshinori,Bao, Ming
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p. 6310 - 6314
(2014/07/21)
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- A ball-milling strategy for the synthesis of benzothiazole, benzimidazole and benzoxazole derivatives under solvent-free conditions
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A convenient solvent-free method for the synthesis of benzothiazole, benzimidazole, and benzoxazole derivatives has been developed using recyclable ZnO-NPs via a ball-milling strategy. The method affords environmentally friendly reaction conditions that score high on the ecoscale with the low E-factor. The process is also highly efficient even on a multi-gram scale and provides easy product isolation.
- Sharma, Hemant,Singh, Narinder,Jang, Doo Ok
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p. 4922 - 4930
(2015/01/08)
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- Ruthenium-catalyzed synthesis of benzoxazoles using acceptorless dehydrogenative coupling reaction of primary alcohols with 2-aminophenol under heterogeneous conditions
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An efficient ruthenium-catalyzed acceptorless dehydrogenative coupling reaction of primary alcohols with 2-aminophenol for one-pot synthesis of benzoxazoles is introduced. The phosphine-functionalized magnetic nanoparticles (PFMNPs; Fe3O4@SiO2@PPh2) as a magnetic recyclable phosphorus ligand in the presence of Ru2Cl 4(CO)6 was found to be an efficient heterogeneous catalytic system for promotion of the designed protocol. The reaction was carried out efficiently with a variety of substrates to give the corresponding products in moderate to good yields.
- Khalafi-Nezhad, Ali,Panahi, Farhad
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p. 1686 - 1692
(2014/06/24)
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- Self-catalyzed direct amidation of ketones: A sustainable procedure for acetaminophen synthesis
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High yielding amination of ketones and benzaldehyde in acid-less conditions has been conducted on several ketones to achieve amides and nitriles. The reactivity of the selected substrates showed to depend on both oximation and Beckmann rearrangement reaction rates. Oximation allows the in-situ production of hydrochloric acid that enables Beckmann rearrangement of the oxime to form the corresponding amide or nitrile. It is noteworthy that, using this one-pot synthetic approach, N-acetyl-4-aminophenol (acetaminophen drug), can be easily synthesized starting from 4-hydroxy-acetophenone in high yield. Acetanilide and ε-caprolactam can be also efficiently synthesized employing this synthetic procedure.
- Rancan, Elia,Aricò, Fabio,Quartarone, Giuseppe,Ronchin, Lucio,Tundo, Pietro,Vavasori, Andrea
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- One-pot oximation-Beckmann rearrangement of ketones and aldehydes to amides of industrial interest: Acetanilide, caprolactam and acetaminophen
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High yielding one-pot oximation-Beckmann rearrangement of ketones to amides in ktrifluoroacetic acid has been conducted on several ketones and aldehydes. The substrate reactivity showed to depend on both oximation and Beckmann rearrangement reaction rate. In this synthetic procedure, trifluoroacetic acid acts as solvent, acid catalyst and organocatalyst and can be easily recycled.
- Aricò, Fabio,Quartarone, Giuseppe,Rancan, Elia,Ronchin, Lucio,Tundo, Pietro,Vavasori, Andrea
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- Self-catalyzed direct amidation of ketones: A sustainable procedure for acetaminophen synthesis
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High yielding amination of ketones and benzaldehyde in acid-less conditions has been conducted on several ketones to achieve amides and nitriles. The reactivity of the selected substrates showed to depend on both oximation and Beckmann rearrangement reaction rates. Oximation allows the in-situ production of hydrochloric acid that enables Beckmann rearrangement of the oxime to form the corresponding amide or nitrile. It is noteworthy that, using this one-pot synthetic approach, N-acetyl-4-aminophenol (acetaminophen drug), can be easily synthesized starting from 4-hydroxy-acetophenone in high yield. Acetanilide and ε-caprolactam can be also efficiently synthesized employing this synthetic procedure.
- Rancan, Elia,Aricò, Fabio,Quartarone, Giuseppe,Ronchin, Lucio,Tundo, Pietro,Vavasori, Andrea
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- Hydrogen-bond-supported dimeric boron complexes of potentially tetradentate β-diketiminate ligands
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Two dimeric boron complexes of potentially tetradentate and trianionic β-diketiminate ligands bearing phenol substituents were prepared and characterized. The synthetic routes employed were designed to circumvent the undesirable formation of β-ketimines and 2-methylbenzoxazoles observed when traditional synthetic routes toward the target β-diketiminate ligands were attempted. The title complexes were isolated via demethylation of β-diketimine ligands and boron difluoride complexes bearing 2-anisole N-aryl substituents using boron tribromide. The resulting complexes were found to contain a unique hydrogen-bond-supported boron-oxygen-boron bridge, as confirmed by X-ray crystallography. The stability of the resulting dimeric structures relative to the corresponding monomeric, tetradentate boron complexes was studied computationally, and theory confirmed that the dimeric structures were strongly favored. The absorption spectra of the dimers were red-shifted relative to the parent β-diketimine ligands. The complexes were irreversibly oxidized and reduced electrochemically and were weakly emissive at low concentrations (Stokes shifts between 23 and 31 nm), showing little solvent dependence.
- Barbon, Stephanie M.,Staroverov, Viktor N.,Boyle, Paul D.,Gilroy, Joe B.
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p. 240 - 250
(2014/01/06)
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- Application of nano SnO2 as a green and recyclable catalyst for the synthesis of 2-aryl or alkylbenzoxazole derivatives under ambient temperature
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Application of nano SnO2 as an efficient and benign catalyst has been explored for the synthesis of 2-aryl or alkylbenzoxazole derivatives via condensation reaction of aldehyde with 2-aminophenol. The reactions proceed under heterogeneous and mild conditions in ethanol at room temperature to provide 2-aryl or alkylbenzoxazoles in high yields.
- Vahdat, Seyed Mohammad,Raz, Shima Ghafouri,Baghery, Saeed
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p. 579 - 585
(2014/07/07)
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- Gold nanoparticles supported on titanium dioxide: An efficient catalyst for highly selective synthesis of benzoxazoles and benzimidazoles
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A highly efficient and selective reaction for the synthesis of 2-substituted benzoxazoles and benzimidazoles catalyzed by Au/TiO2 has been developed via two hydrogen-transfer processes. This reaction has a good tolerance to air and water, a wide substrate scope, and represents a new avenue for practical C-N and C-O bond formation. More importantly, no additional additives, oxidants and reductants are required for the reaction and the catalyst can be recovered and reused readily. This journal is the Partner Organisations 2014.
- Tang, Lin,Guo, Xuefeng,Yang, Yu,Zha, Zhenggen,Wang, Zhiyong
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supporting information
p. 6145 - 6148
(2014/06/09)
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- C-H oxygenation and N-trifluoroacylation of arylamines under metal-free conditions: A convenient approach to 2-aminophenols and N-trifluoroacyl-ortho- aminophenols
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Direct ortho-hydroxylation through C-H oxygenation and N-trifluoroacylation of anilines was achieved in a single step under metal-free conditions by using a combination of TFA and oxone. The method allowed the formation of functionalised amino phenolic compounds such as ortho-hydroxy-N- trifluoroacetanilides in good yields with broad substrate scope.
- Venkateswarlu, Vunnam,Kumar, K. A. Aravinda,Balgotra, Shilpi,Reddy, G. Lakshma,Srinivas,Vishwakarma, Ram A.,Sawant, Sanghapal D.
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supporting information
p. 6641 - 6645
(2014/06/09)
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- Catalytic Staudinger/aza-Wittig sequence by in situ phosphane oxide reduction
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A Staudinger/aza-Wittig reaction sequence is described that is catalytic in phosphorus. Towards this end, the phosphane oxide is reduced in situ by diphenylsilane, which allows for substoichiometric amounts of the catalyst 5-phenyldibenzophosphole to be used. The substrate scope is investigated and benzoxazoles, benzodiazepine imidates and a 2-methoxypyrrole were successfully synthesized. These investigations show that a fast aza-Wittig reaction is required to obtain high yields. A catalytic Staudinger/aza-Wittig reaction sequence, involving in situ phosphane oxide reduction, was successfully developed. Benzoxazoles, benzodiazepine imidates and 2-methoxypyrrole were synthesized without phosphane oxide waste products. Copyright
- Van Kalkeren, Henri A.,Te Grotenhuis, Colet,Haasjes, Frank S.,Hommersom,Rutjes, Floris P. J. T.,Van Delft, Floris L.
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p. 7059 - 7066
(2013/11/06)
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- Tungstate sulfuric acid as an efficient catalyst for the synthesis of benzoxazoles and benzothiazoles under solvent-free conditions
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Tungstate sulfuric acid (TSA) has been found to be an efficient and reusable catalyst for the synthesis of benzoxazole and benzothiazole derivatives via reactions of orthoesters with o-aminophenols or o-aminothiophenols in high yields.
- Farahi, Mahnaz,Karami, Bahador,Azari, Masume
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p. 1029 - 1034
(2013/11/06)
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- A green and efficient protocol for the synthesis of quinoxaline, benzoxazole and benzimidazole derivatives using heteropolyanion-based ionic liquids: As a recyclable solid catalyst
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In this paper, we introduce two nonconventional ionic liquid compounds which are composed of propane sulfonate functionalized organic cations and heteropolyanions as green solid acid catalysts for the highly efficient and green synthesis of 2,3-disubstitutedquinoxaline derivatives. These ionic liquids are in the solid state at room temperature and the synthesis is carried out via the one-pot condensation reaction of various o-phenylenediamine with 1,2-diketone derivatives. Benzoxazole and benzimidazole derivatives were also synthesized by these novel catalysts via the one-pot condensation from reaction orthoester with o-aminophenol (synthesis of benzoxazole derivatives) and ophenylenediamine (synthesis of benzimidazole derivatives). All experiments successfully resulted in the desired products. The described novel synthesis method has several advantages of safety, mild condition, high yields, short reaction times, simplicity and easy workup compared to the traditional method of synthesis.
- Vahdat, Seyed Mohammad,Baghery, Saeed
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p. 618 - 627
(2013/09/12)
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- Intramolecular O-arylation route to 2-substituted benzoxazoles mediated by ferrocene tethered polymer supported ionic liquid phase catalyst
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A novel ferrocene tethered polymer supported ionic liquid phase catalyst has been synthesized and successfully applied for intramolecular O-arylation of o-iodoanilides to corresponding benzoxazoles. The catalyst was easily recovered by simple filtration that greatly simplified the purification step and resulted in quantitative yields, without ionic liquid impurities in the products.
- Jadhav, Jagannath,Gaikwad, Vipul,Kurane, Rajanikant,Salunkhe, Rajashri,Rashinkar, Gajanan
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p. 2920 - 2926
(2013/04/10)
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- Amberlyst-15-catalyzed synthesis of 2-substituted 1,3-benzazoles in water under ultrasound
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A clean and general method has been developed for the synthesis of benzothiazole, benzoxazole, and benzimidazoles using Amberlyst-15 as a recyclable catalyst under ultrasound irradiation in water. The methodology is operationally simple, free from the use of hazardous organic solvents, and does not require the use of inert or anhydrous atmosphere. A number of 1,3-benzazole derivatives were prepared in good to excellent yields by using this methodology.
- Rambabu,Murthi, P. Radha Krishna,Dulla, Balakrishna,Basaveswara Rao,Pal, Manojit
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supporting information
p. 3083 - 3092
(2013/09/12)
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- LRRK2 INHIBITORS
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Provided herein are compounds that inhibit or partially inhibit the activity of leucine rich repeat kinases. Also provided herein are methods of treatment of CNS disorders comprising administration of inhibitors of leucine rich repeat kinases.
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- New approaches to photocatalytic reaction of low concentrations of arylamines in alcohols
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Photocatalytic interactions of a series of arylamines, for example 1,4- phenylenediamine, 1,2-phenylenediamine, 4-aminophenol, and 2-aminophenol, at low concentrations in typical primary alcohols have been investigated in the presence of anatase TiO2 nanopowder. GC-MS analysis of the irradiated solutions showed that, except for 1,2-phenylenediamine, 10 mmol/l alcoholic solutions of the arylamines gave predominately the corresponding imines. Irradiation of 2-aminophenol under these conditions, led to oxidation and dimerization to 2-amino-3Hphenoxazin- 3-one. Springer Science+Business Media B.V. 2012.
- Hosseinnia, Azarmidokht,Keyanpour-Rad, Mansoor
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p. 1411 - 1420
(2012/11/07)
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- Synthesis of benzoxazoles by the copper triflate catalysed reaction of nitriles and o-aminophenols
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An efficient procedure for the synthesis of benzoxazoles by the heteroannulation of nitriles and o-aminophenols in the presence of a catalytic amount of copper(II) trifluoromethanesulfonate, has been developed. This method represents a practical and attractive alternative for the synthesis of both 2-arylbenzoxazoles and 2-alkylbenzoxazoles.
- Tan, Heng,Pan, Cheng-Xue,Xu, Yan-Li,Wang, Heng-Shan,Pan, Ying-Ming
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experimental part
p. 370 - 373
(2012/09/21)
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- The efficient o-benzenedisulfonimide catalysed synthesis of benzothiazoles, benzoxazoles and benzimidazoles
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O-Benzenedisulfonimide has been used to efficiently catalyse the reaction between 2-aminothiophenol, 2-aminophenol, o-phenylenediamine and various ortho esters (28 examples; average yield 90%) or aldehydes (17 examples; average yield 72%) giving the corresponding benzofused azoles in excellent yields. Reaction conditions were very simple. In addition, other carboxylic acid derivatives have been tested and gave good results. The catalyst was easily recovered and reused. ARKAT-USA, Inc.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano
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p. 262 - 279
(2013/02/25)
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- Titanium cation-exchanged montmorillonite as an active heterogeneous catalyst for the Beckmann rearrangement under mild reaction conditions
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Titanium cation-exchanged montmorillonite acts as an efficient heterogeneous catalyst for the Beckmann rearrangement of a wide range of ketoximes including aromatic, aliphatic, and alicyclic ketoximes under mild reaction conditions. After the rearrangement reaction, titanium cation-exchanged montmorillonite is easily separated by simple filtration, and can be reused with retention of high efficiency.
- Mitsudome, Takato,Matsuno, Tsuyoshi,Sueoka, Shoichiro,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 5211 - 5214
(2012/11/07)
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