- BF3·Et2O as a metal-free catalyst for direct reductive amination of aldehydes with amines using formic acid as a reductant
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A versatile metal- and base-free direct reductive amination of aldehydes with amines using formic acid as a reductant under the catalysis of inexpensive BF3·Et2O has been developed. A wide range of primary and secondary amines and diversely substituted aldehydes are compatible with this transformation, allowing facile access to various secondary and tertiary amines in high yields with wide functional group tolerance. Moreover, the method is convenient for the late-stage functionalization of bioactive compounds and preparation of commercialized drug molecules and biologically relevant N-heterocycles. The procedure has the advantages of simple operation and workup and easy scale-up, and does not require dry conditions, an inert atmosphere or a water scavenger. Mechanistic studies reveal the involvement of imine activation by BF3and hydride transfer from formic acid.
- Fan, Qing-Hua,Liu, Xintong,Luo, Zhenli,Pan, Yixiao,Xu, Lijin,Yang, Ji,Yao, Zhen,Zhang, Xin
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supporting information
p. 5205 - 5211
(2021/07/29)
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- Iron(0)-Catalyzed Transfer Hydrogenative Condensation of Nitroarenes with Alcohols: A Straightforward Approach to Benzoxazoles, Benzothiazoles, and Benzimidazoles
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The iron-catalyzed hydrogen transfer strategy has been applied to the redox condensation of o-hydroxynitrobenzene with alcohol, leading to the formation of benzoxazole derivatives. A wide range of 2-substituted benzoxazoles were synthesized in good to excellent yields without the addition of an external redox agent. A series of control experiments provided a plausible mechanism. Furthermore, the reaction system was successfully extended to the synthesis of benzothiazoles and benzimidazoles.
- Putta, Ramachandra Reddy,Chun, Simin,Choi, Seung Hyun,Lee, Seok Beom,Oh, Dong-Chan,Hong, Suckchang
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p. 15396 - 15405
(2020/12/02)
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- Design, Synthesis, and Biological Activity of New N -(Phenylmethyl)-benzoxazol-2-thiones as Macrophage Migration Inhibitory Factor (MIF) Antagonists: Efficacies in Experimental Pulmonary Hypertension
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Macrophage migration inhibitory factor (MIF) is a key pleiotropic mediator and a promising therapeutic target in cancer as well as in several inflammatory and cardiovascular diseases including pulmonary arterial hypertension (PAH). Here, a novel series of N-(phenylmethyl)-benzoxazol-2-thiones 5-32 designed to target the MIF tautomerase active site was synthesized and evaluated for its effects on cell survival. Investigation of structure-activity relationship (SAR) particularly at the 5-position of the benzoxazole core led to the identification of 31 that potently inhibits cell survival in DU-145 prostate cancer cells and pulmonary endothelial cells derived from patients with idiopathic PAH (iPAH-ECs), two cell lines for which survival is MIF-dependent. Molecular docking studies helped to interpret initial SAR related to MIF tautomerase inhibition and propose preferred binding mode for 31 within the MIF tautomerase active site. Interestingly, daily treatment with 31 started 2 weeks after a subcutaneous monocrotaline injection regressed established pulmonary hypertension in rats.
- Le Hiress, Morane,Akagah, Bernardin,Bernadat, Guillaume,Tu, Ly,Thuillet, Rapha?l,Huertas, Alice,Phan, Carole,Fadel, Elie,Simonneau, Gérald,Humbert, Marc,Jalce, Ga?l,Guignabert, Christophe
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p. 2725 - 2736
(2018/04/23)
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- One-pot synthesis of secondary amine via photoalkylation of nitroarenes with benzyl alcohol over Pd/monolayer H1.07Ti1.73O4·H2O nanosheets
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The photoalkylation of nitroarenes with benzyl alcohols in one pot at room temperature and 1 atm N2 was achieved over the Pd/H1.07Ti1.73O4·H2O nanosheets. The sample shows efficient photocatalytic activity with high conversion of nitrobenzene (99%) and selectivity of secondary amine (85%). This flexible photocatalytic system is also applicable to other nitroarenes with high efficiency. Results of in situ FTIR, DRS, and in situ ESR revealed that the benzyl alcohol and nitrobenzene molecules can bind with the surface Lewis and Br?nsted acid sites in the catalyst via the H–O?Ti and NO2?H–O–Ti species. The formation of surface coordination species results in not only the activation of reactant molecules via surface electron transfer, but also the expanded visible light absorption of the catalyst. Moreover, in situ ESR suggested that the surface coordination can also facilitate the formation of oxygen vacancies in catalysts, which can greatly promote the exposure of Lewis sites and enhance the activation of reactant molecules. Finally, a possible hydrogen transfer strategy over the sample is proposed on a molecular level.
- Song, Yujie,Wang, Hao,Liang, Shijing,Yu, Yan,Li, Liuyi,Wu, Ling
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p. 105 - 115
(2018/03/22)
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- Diethylenetriamine-Mediated Direct Cleavage of Unactivated Carbamates and Ureas
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Diethylenetriamine is effective for the direct cleavage of unactivated carbamates and ureas without additional reagents and catalysts. Various carbamates and ureas were cleaved to afford products in good yield, and the reactions were not affected by air or moisture. Unique chemoselective cleavage of carbamate and urea in the presence of amides was also achieved.
- Noshita, Megumi,Shimizu, Yuhei,Morimoto, Hiroyuki,Ohshima, Takashi
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supporting information
p. 6062 - 6065
(2016/12/09)
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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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p. 1770 - 1774
(2016/07/07)
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- Magnetic nanoparticle-supported phosphine gold(i) complex: A highly efficient and recyclable catalyst for the direct reductive amination of aldehydes and ketones
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The direct reductive amination of aldehydes and ketones has been achieved in dichloromethane at room temperature by using a magnetic nanoparticle-supported phosphine gold(i) complex [Fe3O4@SiO2-P-AuCl] as the catalyst and ethyl Hantzsch ester as the hydrogen source, yielding a variety of secondary amines in excellent yields under neutral conditions. The new heterogeneous gold catalyst can be prepared by a simple procedure from commercially readily available reagents and can easily be separated from the reaction mixture by applying an external magnet and recycled at least 10 times without any loss of activity.
- Yang, Weisen,Wei, Li,Yi, Feiyan,Cai, Mingzhong
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p. 4554 - 4564
(2016/07/06)
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- Nano-sized NiLa2O4 spinel-NaBH4-mediated reduction of imines to secondary amines
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Nano-sized NiLa2O4 spinel was produced by thermal decomposition of Ni-La compounds via a sol-gel method. The well-crystallized spinel structure was formed after calcination at 750 °C. The physicochemical properties of the spinel were investigated using differential thermal analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and particle size distribution analysis. The results show that the nanoparticles have regular shapes with well-defined crystal faces and consist of uniform quasi-spherical crystallites of average size 40 nm. The refined unit cell parameters are a = 3.861205 ? and c = 12.6793 ?. This new nano-sized NiLa2O4 spinel is an efficient heterogeneous catalyst for the selective conversion of imines to the corresponding secondary amines in the presence of NaBH4 as a reducing agent, in good to excellent yields. All the reactions were completely chemoselective at room temperature and had relatively short reaction times. Secondary amines with different aryl groups, including those bearing electron-withdrawing or electron-donating groups, were obtained under the optimum reaction conditions. The catalyst was readily recovered and was recycled four times with no significant loss of catalytic activity.
- Shiri, Ali,Soleymanpour, Faezehy,Eshghi, Hossein,Khosravi, Iman
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p. 1191 - 1196
(2015/09/01)
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- Metal-free reductive amination of aldehydes for the synthesis of secondary and tertiary amines
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Reductive amination of aldehydes to produce secondary amines at room-temperature by in situ generated benzimidazoline is discussed. The bonus of the reaction is the formation of pharmaceutically important benzimidazole as a by-product in good yield, which can be recovered from the reaction mixture by simple filtration. The product, secondary amine, is transformed to tertiary amine in the same pot.
- Ambica,Khajuria, Rajni,Saini, Yeshwinder,Kapoor, Kamal K
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p. 1252 - 1259
(2015/11/25)
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- Metal-free TEMPO-promoted C(sp3)-H amination to afford multisubstituted benzimidazoles
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An efficient TEMPO-air/cat. TEMPO-O2 oxidative protocol was developed to synthesize multisubstituted or fused tetracyclic benzimidazoles via a metal-free oxidative C-N coupling between the sp3 C-H and free N-H of readily available N1-benzyl/alkyl-1,2-phenylenediamines.
- Xue, Ding,Long, Ya-Qiu
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p. 4727 - 4734
(2014/06/09)
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- A Pd-catalyzed cascade reaction of N-H insertion and oxidative dehydrogenative aromatization: A new entry to 2-amino-phenols
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A palladium-catalyzed cascade reaction of N-H insertion (NHI) and oxidative dehydrogenative aromatization (ODA) has been developed, which affords a straightforward and efficient way to access the carbazole precursors (2-arylamino-phenols) as well as to prepare 2-alkylamino-phenols from non-aromatic substrates. This journal is the Partner Organisations 2014.
- Ding, Dong,Lv, Xiaobing,Li, Jian,Qiu, Lin,Xu, Guangyang,Sun, Jiangtao
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supporting information
p. 4084 - 4088
(2014/06/10)
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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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p. 6145 - 6148
(2014/06/09)
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- Oxidative transformation of N-substituted 2-aminophenols to 2-substituted benzoxazoles catalyzed by polymer-incarcerated and carbon-stabilized platinum nanoclusters
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The preparation of 2-substituted benzoxazoles was achieved through a sequential aerobic oxidation-enolization-oxidative cyclization reaction of N-substituted 2-aminophenols catalyzed by platinum nanoclusters supported on a polymer/carbon black composite material.
- Yoo, Woo-Jin,Yuan, Hao,Miyamura, Hiroyuki,Kobayashi, Shu
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experimental part
p. 306 - 313
(2012/04/17)
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- Two Component Recyclable Heterogeneous Catalyst, Process for Preparation Thereof and its Use for Preparation of Amines
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The invention describes the development of highly efficient, recyclable two component system, CuAl-hydrotalcite/rac 1,1′-Binaphthalene-2,2′-diol catalytic system for the N-alkylation of electron deficient aryl chlorides in presence of potassium carbonate as a base at room temperature in 3-6 h, wherein the process is provided for the preparation of various secondary amines via C—N coupling reaction of aliphatic amines(aliphatic open chain, acyclic, benzyl amines and heterocyclic amines) with various aryl chlorides.
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Page/Page column 5
(2012/01/13)
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- Diastereospecific coupling of imines by low-valent titanium: An experimental and Computational study
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The reaction of phenylsilane (PhSiH3) and titanium(IV) isopropoxide [Ti(OiPr)4] generates low-valent titanium alkoxides that reduce and reductively couple imines. The C-C coupling reaction is diastereospecific, with exclusive formati
- Kumar, Akshai,Samuelson, Ashoka G.
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supporting information; experimental part
p. 951 - 959
(2011/04/15)
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- Asymmetric synthesis of tetrahydroquinolines with quaternary stereocenters through the Povarov reaction
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The asymmetric Povarov reaction with α-alkyl styrenes as dienophiles was catalyzed by an N,N′-dioxide L4-Sc(OTf)3 complex. Enantiopure tetrahydroquinoline derivatives with a quaternary stereocenter at the C4 position were synthesized for the fi
- Xie, Mingsheng,Liu, Xiaohua,Zhu, Yin,Zhao, Xiaohu,Xia, Yong,Lin, Lili,Feng, Xiaoming
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p. 13800 - 13805
(2012/01/12)
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- Selective alkylation of aminophenols
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O-or N-Alkylated derivatives of aminophenols are important synthetic intermediates in organic synthesis. A series of aminophenols were selectively alkylated on their hydroxyl group in good yields via benzaldehyde protection of the amino group, subsequent alkylation, and hydrolysis; or on their amino group via imination and following reduction. ARKAT USA, Inc.
- Wang, Renchao,Xu, Jiaxi
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experimental part
p. 293 - 299
(2010/10/02)
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- Diastereoselection in the formation of spirocyclic oxindoles by the intramolecular heck reaction
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Diastereoselective double Heck cyclizations of cyclohexene diamides 1 and 3 form contiguous quaternary stereocenters, with diastereoselection being controlled by the trans-diol protecting group. In this, the first in a series of two papers, the origin of
- Overman, Larry E.,Watson, Donald A.
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p. 2587 - 2599
(2007/10/03)
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- A selective reductive amination of aldehydes by the use of Hantzsch dihydropyridines as reductant
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Direct reductive amination of an aldehyde was carried out using a Hantzsch dihydropyridine as the reductant in the presence of a catalytic amount of scandium triflate. The reaction was highly selective towards aldehydes over ketones, and other reducible functional groups did not affect the reaction.
- Itoh, Takashi,Nagata, Kazuhiro,Miyazaki, Michiko,Ishikawa, Hiroyuki,Kurihara, Ayako,Ohsawa, Akio
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p. 6649 - 6655
(2007/10/03)
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- A Facile Reduction Procedure for N,N′-bis[5-Substituted Salicylidene]-m/p-phenylenediamines with Sodium Borohydride-Silica Gel System
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An easy approach involving sodium borohydride/silica gel system offers a fast method of reduction for N,N′-bis[5-substituted salicylidene] m/p-phenylenediamines to the corresponding amines with excellent yield. The observed formation of boron chelates in
- Sridharan,Muthusubramanian,Sivasubramanian
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p. 1087 - 1096
(2007/10/03)
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- Aziridines as a Protecting and Directing Group. Stereoselective Synthesis of (+)-Bromoxone
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(Equation presented) The directing ability of an aziridine group for the epoxidation of adjacent double bonds is demonstrated. The aziridine group is also used to effectively protect a double bond in a cycloenone system for a short synthesis of the title
- Barros, M. Teresa,Matias, Pedro M.,Maycock, Christopher D.,Ventura, M. Rita
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p. 4321 - 4323
(2007/10/03)
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- Utilization of lithium triethylborohydride as a selective N-acyl deprotecting agent
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Lithium triethylborohydride has been found to be a superior and selective reagent for the removal of tertiary N-acyl protecting groups. The reagent selectively removes tertiary amide acyl functionality without affecting secondary amide functionality even when they are present in the same molecule. Some tertiary carbamates may be also removed under the same conditions.
- Tanaka, Hideyuki,Ogasawara, Kunio
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p. 4417 - 4420
(2007/10/03)
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- New substituted 1,4-benzoxazine derivatives with potential intracellular calcium activity
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Substituted 1,4-benzoxazines bearing an amino side chain at the 2- position were prepared and were found to have a moderate activity on intracellular calcium. Of the compounds studied it was found that those which possess a homoveratrylamino moiety exhibi
- Bourlot, Anne-Sophie,Sánchez, Isabel,Dureng, Georges,Guillaumet, Gérald,Massingham, Roy,Monteil, André,Winslow, Eileen,Pujol, M. Dolors,Mérour, Jean-Yves
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p. 3142 - 3158
(2007/10/03)
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- Synthesis of 3-Substitued Benzoxazoline-2-thiones
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Several methods for the preparation of 3-substitued benzoxazoline-2-hiones (1) were examined.Method B via the thiation of 3-substitued benzoxazoline-2-one (5) with phosphorus pentasulfide was found to be applicable to the preparation of most analogs of 1, with a few expections.Method C via the cyclization of 2-(alkylamino)phenol (7) with potassium O-methyldithiocarbonate was suitable for the preparation of analogs with a group sensitive to high temperature of with an aryl- (including aromatic heterocyclic ring) methyl group.In addition, the reaction of benzoxazoline-2-thione (2) with acetals such as 1-ethoxyisochroman, 2-ethoxytetrahydrofuran, and ethoxytetraydropyran, or with Michael acceptors such as 2,3-dihydrofuran and 2H-3,4-dihydropyran, gave 3-substitued benzoxazoline-2-thione (1d-f).
- Yamato, Masatoshi,Takeuchi, Yasuo,Hashigaki, Kuniko,Hattori, Kyoko,Muroga, Eiko,Hirota, Takashi
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p. 1733 - 1737
(2007/10/02)
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- Method of topically treating inflammation
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This invention describes a method of treating inflammation in warmblooded animals by topically administering an effective amount of benzylamine and its derivatives.
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