- A NOVEL ROUTE TO QUINOLINE DERIVATIVES FROM 1,3-PROPANEDIOL AND AMINOARENES: RUTHENIUM CATALYZED HETEROCYCLIZATION UNDER NON-ACIDIC CONDITIONS
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Ruthenium trichloride hydrate combined with tributylphosphine catalyzes the reaction between 1,3-propanediol and an aminoarene at 180 deg C, providing a novel route to quinoline derivatives under non-acidic conditions.
- Tsuji, Yashushi,Nishimura, Hideo,Huh, Keun-Tae,Watanabe, Yoshihisa
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- Organocatalytic Enantioselective Functionalization of Hydroxyquinolines through an Aza-Friedel-Crafts Alkylation with Isatin-derived Ketimines
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A highly enantioselective addition of hydroxyquinolines to isatin-derived ketimines has been realized using a quinine-derived thiourea organocatalyst. The reaction affords chiral 3-amino-2-oxindoles bearing a quinoline moiety with a quaternary stereocenter in high yields (up to 98%) and excellent enantioselectivities (up to 99%). Moreover, we can extend this methodology for the enantioselective functionalization of 5-hydroxyisoquinoline. This methodology represents, to the best of our knowledge, the first enantioselective addition of hydroxyquinolines to imines. (Figure presented.).
- Vila, Carlos,Rendón-Pati?o, Alejandra,Montesinos-Magraner, Marc,Blay, Gonzalo,Mu?oz, M. Carmen,Pedro, José R.
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- Picomole-Scale Real-Time Photoreaction Screening: Discovery of the Visible-Light-Promoted Dehydrogenation of Tetrahydroquinolines under Ambient Conditions
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The identification of new photocatalytic pathways expands our knowledge of chemical reactivity and enables new environmentally friendly synthetic applications. However, the development of miniaturized screening procedures/platforms to expedite the discovery of photochemical reactions remains challenging. Herein, we describe a picomole-scale, real-time photoreaction screening platform in which a handheld laser source is coupled with nano-electrospray ionization mass spectrometry. By using this method, we discovered an accelerated dehydrogenation pathway for the conversion of tetrahydroquinolines into the corresponding quinolines. This transformation is readily promoted by an off-the-shelf [Ru(bpy)3]Cl2?6 H2O complex in air at ambient temperature in direct sunlight, or with the aid of an energy-saving lamp. Moreover, radical cations and trans-dihydride intermediates captured by the screening platform provided direct evidence for the mechanism of the photoredox reaction.
- Chen, Suming,Wan, Qiongqiong,Badu-Tawiah, Abraham K.
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- Method for realizing oxidative dehydrogenation of nitrogen-containing heterocyclic ring by using biomass-based carbon material
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The invention provides a method for realizing oxidative dehydrogenation of a nitrogen-containing heterocyclic ring by using a biomass-based carbon material, and belongs to the field of organic synthesis. According to the method, the raw materials of the biomass-based carbon material comprise wheat, sorghum, rice, corn straw, wheat straw, peanut shells, sesame shells, bean shells and the like, and are crushed and then ground into powder, the powder is fully mixed with an inorganic alkali, and calcination is performed in an inert gas atmosphere to prepare the biomass-based carbon material; and by using air as an oxygen source, at a temperature of 50-120 DEG C, oxidative dehydrogenation of nitrogen-containing heterocyclic compounds to synthesize quinoline compounds, isoquinoline compounds, acridine compounds, quinazoline compounds, indole compounds, imine compounds, and even quinoline compounds with pharmaceutical activity can be achieved. According to the present invention, easily available wheat flour is adopted as a raw material to prepare a non-metal catalyst, the alkali is not added during the reaction process, and a remarkable industrial application prospect is achieved.
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Paragraph 0010-0011; 0022-0023
(2021/06/26)
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- Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
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The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
- Fiorio, Jhonatan L.,Rossi, Liane M.
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p. 312 - 318
(2021/01/29)
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- Metal-Free Deoxygenation of Amine N-Oxides: Synthetic and Mechanistic Studies
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We report herein an unprecedented combination of light and P(III)/P(V) redox cycling for the efficient deoxygenation of aromatic amine N-oxides. Moreover, we discovered that a large variety of aliphatic amine N-oxides can easily be deoxygenated by using only phenylsilane. These practically simple approaches proceed well under metal-free conditions, tolerate many functionalities and are highly chemoselective. Combined experimental and computational studies enabled a deep understanding of factors controlling the reactivity of both aromatic and aliphatic amine N-oxides.
- Lecroq, William,Schleinitz, Jules,Billoue, Mallaury,Perfetto, Anna,Gaumont, Annie-Claude,Lalevée, Jacques,Ciofini, Ilaria,Grimaud, Laurence,Lakhdar, Sami
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p. 1237 - 1242
(2021/06/01)
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- Highly Chemoselective Deoxygenation of N-Heterocyclic N-Oxides Using Hantzsch Esters as Mild Reducing Agents
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Herein, we disclose a highly chemoselective room-temperature deoxygenation method applicable to various functionalized N-heterocyclic N-oxides via visible light-mediated metallaphotoredox catalysis using Hantzsch esters as the sole stoichiometric reductant. Despite the feasibility of catalyst-free conditions, most of these deoxygenations can be completed within a few minutes using only a tiny amount of a catalyst. This technology also allows for multigram-scale reactions even with an extremely low catalyst loading of 0.01 mol %. The scope of this scalable and operationally convenient protocol encompasses a wide range of functional groups, such as amides, carbamates, esters, ketones, nitrile groups, nitro groups, and halogens, which provide access to the corresponding deoxygenated N-heterocycles in good to excellent yields (an average of an 86.8% yield for a total of 45 examples).
- An, Ju Hyeon,Kim, Kyu Dong,Lee, Jun Hee
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supporting information
p. 2876 - 2894
(2021/02/01)
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- Copper-Catalyzed Methoxylation of Aryl Bromides with 9-BBN-OMe
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A Cu-catalyzed cross-coupling reaction between aryl bromides and 9-BBN-OMe to provide aryl methyl ethers under mild conditions is reported. The oxalamide ligand BHMPO plays a key role in the transformation. Various functional groups on bromobenzenes are well tolerated, providing the desired anisole products in moderate to high yields.
- Li, Chen,Song, Zhi-Qiang,Wang, Dong-Hui,Wang, Jing-Ru
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supporting information
p. 8450 - 8454
(2021/11/17)
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- CgPhen-DalPhos Enables the Nickel-CatalyzedO-Arylation of Tertiary Alcohols with (Hetero)Aryl Electrophiles
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While the Ni-catalyzed cross-coupling of primary or secondary aliphatic alcohols and (hetero)aryl electrophiles is known, related cross-couplings involving tertiary aliphatic alcohols, with a broad scope, are challenging. Herein we disclose that a NiIIprecatalyst featuring the ligand CgPhen-DalPhos is unusual in its ability to promote the C-O cross-coupling of tertiary aliphatic alcohols with (hetero)aryl halides (Cl, Br, and I) or phenol derivatives (OMs and OPiv). An exploration of substrate scope and competition experiments help to shed light on the capabilities and reactivity preferences of this catalyst system.
- Morrison, Kathleen M.,McGuire, Ryan T.,Ferguson, Michael J.,Stradiotto, Mark
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p. 10878 - 10884
(2021/09/08)
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- Iron(II)-Catalyzed Aerobic Biomimetic Oxidation of N-Heterocycles
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Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydrogenation process, involving several electron-transfer steps, is inspired by oxidations occurring in the respiratory chain. An environmentally friendly and inexpensive iron catalyst together with a hydroquinone/cobalt Schiff base hybrid catalyst as electron-transfer mediator were used for the substrate-selective dehydrogenation reaction of various N-heterocycles. The method shows a broad substrate scope and delivers important heterocycles in good-to-excellent yields.
- Manna, Srimanta,Kong, Wei-Jun,B?ckvall, Jan-E.
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supporting information
p. 13725 - 13729
(2021/09/08)
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- Visible light mediated selective oxidation of alcohols and oxidative dehydrogenation of N-heterocycles using scalable and reusable La-doped NiWO4nanoparticles
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Visible light-mediated selective and efficient oxidation of various primary/secondary benzyl alcohols to aldehydes/ketones and oxidative dehydrogenation (ODH) of partially saturated heterocycles using a scalable and reusable heterogeneous photoredox catalyst in aqueous medium are described. A systematic study led to a selective synthesis of aldehydes under an argon atmosphere while the ODH of partially saturated heterocycles under an oxygen atmosphere resulted in very good to excellent yields. The methodology is atom economical and exhibits excellent tolerance towards various functional groups, and broad substrate scope. Furthermore, a one-pot procedure was developed for the sequential oxidation of benzyl alcohols and heteroaryl carbinols followed by the Pictet-Spengler cyclization and then aromatization to obtain the β-carbolines in high isolated yields. This methodology was found to be suitable for scale up and reusability. To the best of our knowledge, this is the first report on the oxidation of structurally diverse aryl carbinols and ODH of partially saturated N-heterocycles using a recyclable and heterogeneous photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Balasubramaniam, K. K.,Baskar, B.,Divya, P.,Mani Rahulan, K.,Rahman, Abdul,Sridhar, R.,Srinath, S.
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p. 5990 - 6007
(2021/08/24)
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- Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
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Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.
- Liu, Shuyang,Tian, Miao,Bu, Xiubin,Tian, Hua,Yang, Xiaobo
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supporting information
p. 7738 - 7744
(2021/05/07)
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- Monomeric vanadium oxide: A very efficient species for promoting aerobic oxidative dehydrogenation of N-heterocycles
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Monomeric active species are very interesting in heterogeneous catalysis. In this work, we proposed a method to prepare VOx-NbOy@C catalysts, which involve the one-pot hydrothermal synthesis of inorganic/organic hybrid materials containing V/Nb followed by thermal treatment under a reducing atmosphere. The prepared catalysts were characterized using different techniques, such as high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy. It was shown that monomeric VOx species were dispersed homogeneously in the catalysts. The VOx-NbOy@C catalysts displayed high performance in the aerobic oxidative dehydrogenation of N-heterocycles to aromatic heterocycles. It was demonstrated that the selectivity of reaction over the catalyst with a very small amount of V (0.07 wt%) was much higher than that over the NbOy@C, and the catalyst also exhibited excellent stability in the reaction. The detailed study indicated that monomeric VO2 species were the most effective for promoting the reaction. This journal is
- Xie, Zhenbing,Chen, Bingfeng,Zheng, Lirong,Peng, Fangfang,Liu, Huizhen,Han, Buxing
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p. 431 - 437
(2021/01/11)
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- Geometric and electronic effects on the performance of a bifunctional Ru2P catalyst in the hydrogenation and acceptorless dehydrogenation of N-heteroarenes
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The development of bifunctional catalysts for the efficient hydrogenation and acceptorless dehydrogenation of N-heterocycles is a challenge. In this study, Ru2P/AC effectively promoted reversible transformations between unsaturated and saturated N-heterocycles affording yields of 98% and 99%, respectively. Moreover, a remarkable enhancement in the reusability of Ru2P/AC was observed compared with other Ru-based catalysts. According to density functional theory calculations, the superior performance of Ru2P/AC was ascribed to specific synergistic factors, namely geometric and electronic effects induced by P. P greatly reduced the large Ru-Ru ensembles and finely modified the electronic structures, leading to a low reaction barrier and high desorption ability of the catalyst, further boosting the hydrogenation and acceptorless dehydrogenation processes.
- Shao, Fangjun,Yao, Zihao,Gao, Yijing,Zhou, Qiang,Bao, Zhikang,Zhuang, Guilin,Zhong, Xing,Wu, Chuan,Wei, Zhongzhe,Wang, Jianguo
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p. 1185 - 1194
(2021/02/16)
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- Catalytic Deoxygenation of Amine and Pyridine N-Oxides Using Rhodium PCcarbeneP Pincer Complexes
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Rhodium PCcarbeneP pincer complexes 1-L (L = PPh3, PPh2(C6F5), PCy3) readily facilitate deoxygenation of amine and pyridine N-oxides. The resulting complexes exhibit δ2-C= O coordination of the resulting keto POP pincer ligand. These δ2-Ca? O linkages in the metalloepoxide complexes are readily reduced by isopropyl alcohol and various benzylic alcohols. Thus, efficient catalytic deoxygenation of amine and pyridine N-oxides is possible using complexes 1-L and isopropyl alcohol. This represents a pioneering example of PCcarbeneP pincer complexes being used as catalysts for catalytic deoxygenation.
- Tinnermann, Hendrik,Sung, Simon,Cala, Beatrice A.,Gill, Hashir J.,Young, Rowan D.
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p. 797 - 803
(2020/03/13)
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- Catalyst-Free N-Deoxygenation by Photoexcitation of Hantzsch Ester
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A mild and operationally simple protocol for the deoxygenation of a variety of heteroaryl N-oxides and nitroarenes has been developed. A mixture of substrate and Hantzsch ester is proposed to result in an electron donor-acceptor complex, which upon blue-light irradiation undergoes photoinduced electron transfer between the two reactants to afford the products. N-oxide deoxygenation is demonstrated with 22 examples of functionally diverse substrates, and the chemoselective reduction of nitroarenes to the corresponding hydroxylamines is also shown.
- Cardinale, Luana,Jacobi Von Wangelin, Axel,Konev, Mikhail O.
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supporting information
(2020/02/15)
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- Superhydrophobic nickel/carbon core-shell nanocomposites for the hydrogen transfer reactions of nitrobenzene and N-heterocycles
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In this work, catalytic hydrogen transfer as an effective, green, convenient and economical strategy is for the first time used to synthesize anilines and N-heterocyclic aromatic compounds from nitrobenzene and N-heterocycles in one step. Nevertheless, how to effectively reduce the possible effects of water on the catalyst by removal of the by-product water, and to further introduce water as the solvent based on green chemistry are still challenges. Since the structures and properties of carbon nanocomposites are easily modified by controllable construction, a one step pyrolysis process is used for controllable construction of micro/nano hierarchical carbon nanocomposites with core-shell structures and magnetic separation performance. Using various characterization methods and model reactions the relationship between the structure of Ni?NCFs (nickel-nitrogen-doped carbon frameworks) and catalytic performance was investigated, and the results show that there is a positive correlation between the catalytic performance and hydrophobicity of catalysts. Besides, the possible catalytically active sites, which are formed by the interaction of pyridinic N and graphitic N in the structure of nitrogen-doped graphene with the surfaces of Ni nanoparticles, should be pivotal to achieving the relatively high catalytic performance of materials. Due to its unique structure, the obtained Ni?NCF-700 catalyst with superhydrophobicity shows extraordinary performances toward the hydrogen transfer reaction of nitrobenzene and N-heterocycles in the aqueous state; meanwhile, it was also found that Ni?NCF-700 still retained its excellent catalytic activity and structural integrity after three cycles. Compared with traditional catalytic systems, our catalytic systems offer a highly effective, green and economical alternative for nitrobenzene and N-heterocycle transformation, and may open up a new avenue for simple construction of structure and activity defined carbon nanocomposite heterogeneous catalysts with superhydrophobicity.
- Duan, Zhiying,Liu, Fangfang,Pang, Shaofeng,Su, Qiong,Wang, Yanbin,Xie, Xin,Zhang, Ping,Zhang, Yujing,Zhou, Feng
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p. 1996 - 2010
(2020/04/07)
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- Catalytic Aerobic Dehydrogenatin of N-Heterocycles by N-Hydoxyphthalimide
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Catalytic methods for the aerobic dehydrogenation of N-heterocycles are reported. In most cases, indoles are accessed efficiently from indolines using catalytic N-hydroxyphthalimide (NHPI) as the sole additive under air. Further studies revealed an improved catalytic system of NHPI and copper for the preparation of other heteroaromatics, for example quinolines. (Figure presented.).
- Chen, Weidong,Tang, Hao,Wang, Weilin,Fu, Qiang,Luo, Junfei
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supporting information
p. 3905 - 3911
(2020/08/10)
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- Method for preparation of quinoline compounds
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The invention discloses a green preparation method of quinoline compounds. According to the method, cheap and easily available copper salt and N-hydroxyphthalimide are used as catalysts, oxygen is used as an oxidizing agent, oxidation of tetrahydroquinoline compounds is performed in an organic solvent, and synthesis of quinoline compounds is realized. The method has the advantages of simple reaction operation, low reaction cost, high yield, low metal pollution and the like.
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Paragraph 0067-0069
(2020/11/12)
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- Reusable, homogeneous water soluble photoredox catalyzed oxidative dehydrogenation of N-heterocycles in a biphasic system: Application to the synthesis of biologically active natural products
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Herein, a simple and efficient method for the oxidative dehydrogenation (ODH) of tetrahydro-β-carbolines, indolines and tetrahydro-(iso)quinolines is described using a reusable, homogeneous cobalt-phthalocyanine photoredox catalyst in a biphasic medium. A biphasic system offers an advantage of easy separation of the product and an efficient reusability of the homogeneous photoredox catalyst. Also, the current system significantly helps to overcome the solubility issue of the substrate and catalyst at room temperature. Its potential applications to organic transformations are demonstrated by the synthesis of various biologically active N-heterocycles such as indoles, (iso)quinolines and β-carbolines and natural products such as eudistomin U, norharmane, and harmane and precursors to perlolyrine and flazin. Without isolation and purification, the catalyst solution can be reused up to 5 times with almost comparable reactivity. Furthermore, the efficiency of the reaction was demonstrated on a gram scale. To the best of our knowledge, this is the first report on ODH reactions using a non noble, reusable and homogeneous cobalt photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Baskar, B.,Mariappan, M.,Prasanth, Arun,Sridhar, R.,Srinath, S.
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p. 2575 - 2587
(2020/05/13)
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- Visible-Light-Promoted Efficient Aerobic Dehydrogenation of N-Heterocycles by a Tiny Organic Semiconductor Under Ambient Conditions
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An efficient reusable catalytic system has been developed based on perylene diimide (PDI) organic semiconductor for the aerobic dehydrogenation of N-heterocycles with visible light. This practical catalytic system without any additives proceeds under ambient conditions. The minute aggregates of PDI molecules on the surface of SiO2 nanospheres form tiny organic semiconductors, resulting in high-efficiency photo-oxidative activity. Notably, the robustness of this method is demonstrated by the synthesis of a wide range of N-heteroarenes, gram-scale experiments as well as reusability tests.
- Su, Chenliang,Yu, Kunyi,Zhang, Hanjie,Zhu, Yongfa
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supporting information
p. 1956 - 1960
(2020/04/10)
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- Rh/TiO2-Photocatalyzed Acceptorless Dehydrogenation of N-Heterocycles upon Visible-Light Illumination
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TiO2 is an effective and extensively employed photocatalyst, but its practical use in visible-light-mediated organic synthesis is mainly hindered by its wide band gap energy. Herein, we have discovered that Rh-photodeposited TiO2 nanoparticles selectively dehydrogenate N-heterocyclic amines with the concomitant generation of molecular hydrogen gas in an inert atmosphere under visible light (λmax = 453 nm) illumination at room temperature. Initially, a visible-light-sensitive surface complex is formed between the N-heterocycle and TiO2. The acceptorless dehydrogenation of N-heterocycles is initiated by direct electron transfer from the HOMO energy level of the amine via the conduction band of TiO2 to the Rh nanoparticle. The reaction condition was optimized by examining different photodeposited noble metals on the surface of TiO2 and solvents, finding that Rh0 is the most efficient cocatalyst, and 2-propanol is the optimal solvent. Structurally diverse N-heterocycles such as tetrahydroquinolines, tetrahydroisoquinolines, indolines, and others bearing electron-deficient as well as electron-rich substituents underwent the dehydrogenation in good to excellent yields. The amount of released hydrogen gas evinces that only the N-heterocyclic amines are oxidized rather than the dispersant. This developed method demonstrates how UV-active TiO2 can be employed in visible-light-induced synthetic dehydrogenation of amines and simultaneous hydrogen storage applications.
- Bahnemann, Detlef W.,Balayeva, Narmina O.,Dillert, Ralf,Mamiyev, Zamin,Zheng, Nan
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p. 5542 - 5553
(2020/08/25)
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- DMSO/t-BuONa/O2-Mediated Aerobic Dehydrogenation of Saturated N-Heterocycles
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Aromatic N-heterocycles such as quinolines, isoquinolines, and indolines are synthesized via sodium tert-butoxide-promoted oxidative dehydrogenation of the saturated heterocycles in DMSO solution. This reaction proceeds under mild reaction conditions and has a good functional group tolerance. Mechanistic studies suggest a radical pathway involving hydrogen abstraction of dimsyl radicals from the N-H bond or α-C-H of the substrates and subsequent oxidation of the nitrogen or α-aminoalkyl radicals.
- Cai, Hu,Tan, Wei,Xie, Yongfa,Yang, Ruchun,Yue, Shusheng
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p. 7501 - 7509
(2020/07/07)
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- CONVERSION OF TETRAHYDROQUINOLINE DERIVATIVES TO QUINOLINE USING AZOCOMPOUND
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The present invention relates to a method of converting tetrahydroquinoline derivatives into quinoline using an azo compound and, more specifically, to a conversion method which is performed in a deuterium chloroform (CDCl_3) or chloroform (CHCl_3) solution including dialkyl azodicarboxylate, which is a method of producing quinoline through a dehydrogenation reaction of 1,2,3,4-tetrahydroquinoline. According to the present invention, a dehydrogenation reaction rate is dependent on the electronic and steric properties of used dialkyl azodicarboxylate; and chloroform shows better results than other substances in solvents screened with diethyl azodicarboxylate. Various types of 1,2,3,4-tetrahydroquinoline undergo the dehydration reaction of the present invention to produce the corresponding quinoline in a yield of at least 90%; and diethyl hydrazo dicarboxylate, which is a reduced form of diethyl azodicarboxylate, is readily separated and recyclable.COPYRIGHT KIPO 2020
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Paragraph 0041-0042; 0065; 0112-0116
(2020/03/10)
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- Visible-Light-Mediated Photocatalytic Aerobic Dehydrogenation of N-heterocycles by Surface-Grafted TiO2 and 4-amino-TEMPO
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Herein, the visible-light-induced dehydrogenation of N-heterocycles such as tetrahydroquinolines, tetrahydroisoquinolines, and indolines in O2-containing suspensions of a commercially available titanium dioxide photocatalyst yielding the corresponding heteroarenes is presented. 4-Amino-2,2,6,6-tetramethylpipiridinyloxyl (4-amino-TEMPO) was found to exhibit a beneficial role, as it increased the yield and improved the selectivity of the dehydrogenation reaction. Both the selectivity and the yield are further enhanced by grafting 0.1 wt % of Ni(II) ions onto the TiO2 surface. It is proposed that the basic reactant adsorbs at Lewis acid sites present at the TiO2 surface. The dehydrogenation reaction is initiated by visible-light excitation of the resulting surface complex and a subsequent single-electron transfer from the excited N-heterocycle via the conduction band of TiO2 to O2. Ni(II) ions possibly serve as an electron transfer bridge between the conduction band of TiO2 and O2, while the TEMPO derivative is assumed to act as a selective redox mediator involved in reactions of the generated reactive oxygen species.
- Balayeva, Narmina O.,Zheng, Nan,Dillert, Ralf,Bahnemann, Detlef W.
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p. 10694 - 10704
(2019/11/14)
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- A Reusable Cobalt Catalyst for Reversible Acceptorless Dehydrogenation and Hydrogenation of N-Heterocycles
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The development of robust catalytic systems based on base-metals for reversible acceptorless dehydrogenation (ADH) and hydrogenation of feedstock chemicals is very important in the context of ‘hydrogen storage’. Herein, we report a highly efficient reusable cobalt-based heterogeneous catalyst for reversible dehydrogenation and hydrogenation of N-heterocycles. Both the ADH and the hydrogenation processes operate under mild, benign conditions.
- Jaiswal, Garima,Subaramanian, Murugan,Sahoo, Manoj K.,Balaraman, Ekambaram
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p. 2449 - 2457
(2019/05/10)
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- Room temperature catalytic dehydrogenation of cyclic amines with the liberation of H2 using water as a solvent
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Catalytic dehydrogenation of cyclic amines, in particular partially saturated N-heterocycles to N-heterocyclic arenes, with the removal of molecular hydrogen as the sole byproduct in water is reported. This dehydrogenation reaction proceeds smoothly under very mild and benign conditions and operates at room temperature. This distinctive reactivity has been achieved under dual catalytic conditions by merging the visible-light active [Ru(bpy)3]2+ as the photoredox catalyst and a newly synthesized cobalt complex as the proton-reduction catalyst. A detailed mechanistic study (control experiments, electrochemical studies, UV-visible experiments) is presented for the present dual catalysis.
- Sahoo, Manoj K.,Balaraman, Ekambaram
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supporting information
p. 2119 - 2128
(2019/04/26)
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- Corrigendum: Organo-Photoredox Catalyzed Oxidative Dehydrogenation of N-Heterocycles (Chemistry - A European Journal, (2017), 23, 57, (14167-14172), 10.1002/chem.201703642)
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The authors have been alerted to an error that was unfortunately missed at the time of publication. Table was duplicated with Table 4. The correct version of Table 2 is shown below. The authors apologise for any inconvenience caused. Organo-photoredox catalyzed oxidative dehydrogenation of tetrahydroquinolines (THQ).[a,b] (Table presented.) [a] Reaction conditions: 1 (0.5 mmol), rose bengal (1.0 mol %), N,N-dimethylacetamide (2.0 mL), open air atmosphere under visible-light irradiation at room temperature for 24 h. [b] Isolated yields. [c] 0.1 mol % of photoredox catalyst for 28 h.
- Sahoo, Manoj K.,Jaiswal, Garima,Rana, Jagannath,Balaraman, Ekambaram
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p. 7038 - 7038
(2019/05/17)
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- Nitrogen-coordinated cobalt nanocrystals for oxidative dehydrogenation and hydrogenation of N-heterocycles
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To endow non-noble metals with the high catalytic activity that is typically exhibited by noble metals is the central yet challenging aim for substituting noble metals. In this regard, by exploiting the coordination effect of nitrogen, we prepared cobalt nanocrystals stabilized by nitrogen-doped graphitized carbon (Co NCs/N-C). The obtained Co NC/N-C catalyst showed extraordinary performances toward both oxidative dehydrogenation of N-heterocycles and its reverse hydrogenation process under extremely mild conditions. A nearly quantitative conversion could be achieved for oxidative dehydrogenation even at room temperature (25 °C), for which the coordination effect of nitrogen is responsible: the interaction of Co-N induces a partial positive charge on the Co surface, thereby promoting the reaction. In contrast, cobalt nanocrystals supported by pristine carbon (Co NCs/C) proved to be inactive for oxidative dehydrogenation, owing to the lack of nitrogen. Moreover, in Co NCs/N-C, the N-doped graphitized carbon formed a protective layer for Co NCs, which preserved the active valence of Co species and prevented the catalyst from leaching. It was found that the catalyst still retained its excellent catalytic activity after five regeneration cycles; in comparison, its cobaltous oxide counterpart (CoOx/N-C) was barely active. As for the mechanism, electron paramagnetic resonance (EPR) analysis revealed the formation of superoxide anion radicals during the dehydrogenation process. Interestingly, the pressure of feed hydrogen had little effect on the hydrogenation process. Our Co NC/N-C catalyst is capable of activating molecular oxygen and hydrogen as effectively as noble metals; the coordination effect of nitrogen and the protection by the carbon layer in combination confer tremendous potential on the Co NCs/N-C for substituting noble-metal-based catalysts and soluble catalysts for homogeneous reactions.
- Wu, Yue,Chen, Zheng,Cheong, Weng-Chon,Zhang, Chao,Zheng, Lirong,Yan, Wensheng,Yu, Rong,Chen, Chen,Li, Yadong
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p. 5345 - 5352
(2019/05/29)
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- Visible-Light Photocatalyzed Deoxygenation of N-Heterocyclic N-Oxides
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A scalable and operationally simple method is described that allows for the chemoselective deoxygenation of a wide range of N-heterocyclic N-oxides (a total of 36 examples). This visible-light-induced protocol features the use of only commercially available reagents, room-temperature conditions, and unprecedented chemoselective removal of the oxygen atom in a quinoline N-oxide in the presence of a pyridine N-oxide in the same molecule through the judicious selection of a photocatalyst.
- Kim, Kyu Dong,Lee, Jun Hee
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supporting information
p. 7712 - 7716
(2019/01/03)
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- Exploiting ancillary ligation to enable nickel-catalyzed c-o cross-couplings of aryl electrophiles with aliphatic alcohols
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The use of (L)Ni(o-tolyl)Cl precatalysts (L = PAd-DalPhos or CyPAd-DalPhos) enables the C(sp2)-O cross-coupling of primary, secondary, or tertiary aliphatic alcohols with (hetero)aryl electrophiles, including unprecedented examples of such nickel-catalyzed transformations employing (hetero)aryl chlorides, sulfonates, and pivalates. In addition to offering a competitive alternative to palladium catalysis, this work establishes the feasibility of utilizing ancillary ligation as a complementary means of promoting challenging nickel-catalyzed C(sp2)-O cross-couplings, without recourse to precious-metal photoredox catalytic methods.
- MacQueen, Preston M.,Tassone, Joseph P.,Diaz, Carlos,Stradiotto, Mark
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supporting information
p. 5023 - 5027
(2018/04/24)
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- High efficiency microwave-assisted synthesis of quinoline from acrolein diethyl acetal and aniline utilizing Ni/Beta catalyst
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A facile and solvent-free microwave-assisted approach to quinoline was developed by utilizing both acrolein diethyl acetal and aniline as reagents, firstly employing Ni/Beta zeolite as mild, ecofriendly and low-cost solid catalyst. As high as 83% yield of quinoline was quickly achieved at a short microwave time. The results indicated that the effect of Ni on Beta zeolite not only significantly promoted conversion of acrolein diethyl acetal to effective intermediate but also dramatically accelerated dehydrogenation rate of tetrahydroquinoline/dihydroquinoline to quinoline.
- Li, An,Yang, Zan,Yang, Tao,Luo, Cai-Wu,Chao, Zi-Sheng,Zhou, Cong-Shan
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- Efficient dehydrogenation of 1,2,3,4-tetrahydroquinolines mediated by dialkyl azodicarboxylates
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Various dialkyl azodicarboxylates were investigated for the dehydrogenation of 1,2,3,4-tetrahydroquinolines to quinolines. The dehydrogenation rates varied according to the electronic and steric nature of the used dialkyl azodicarboxylates. Among solvents screened with diethyl azodicarboxylate, chloroform exhibited superior results to others. A variety of 1,2,3,4-tetrahydroquinolines underwent the present dehydrogenation to produce the corresponding quinolines. Diethyl hydrazodicarboxylate, which is a reduced species of diethyl azodicarboxylate, was easily separated for recycle.
- Bang, Saet Byeol,Kim, Jinho
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supporting information
p. 1291 - 1298
(2018/04/05)
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- Acceptorless Dehydrogenation of N-Heterocycles and Secondary Alcohols by Ru(II)-NNC Complexes Bearing a Pyrazoyl-indolyl-pyridine Ligand
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Ruthenium(II) hydride complexes bearing a pyrazolyl-(2-indol-1-yl)-pyridine ligand were synthesized and structurally characterized by NMR analysis and X-ray single crystal crystallographic determinations. These complexes efficiently catalyzed acceptorless dehydrogenation of N-heterocycles and secondary alcohols, respectively, exhibiting highly catalytic activity with a broad substrate scope. The present work has established a strategy to construct highly active transition metal complex catalysts and provides an atom-economical and environmentally benign protocol for the synthesis of aromatic N-heterocyclic compounds and ketones.
- Wang, Qingfu,Chai, Huining,Yu, Zhengkun
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p. 584 - 591
(2018/03/08)
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- Oxidation Potential Tunable Organic Molecules and Their Catalytic Application to Aerobic Dehydrogenation of Tetrahydroquinolines
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In this work, oxidation potential tunable organic molecules, alkyl 2-phenyl hydrazocarboxylates, were disclosed. The exquisite tuning of their oxidation potentials facilitated a catalytic dehydrogenation of 1,2,3,4-tetrahydroquinolines in the presence of Mn(Pc) and O2.
- Jung, Dahyeon,Jang, Seol Heui,Yim, Taeeun,Kim, Jinho
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supporting information
p. 6436 - 6439
(2018/10/15)
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- Aerobic oxidative dehydrogenation of N-heterocycles catalyzed by cobalt porphyrin
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An efficient catalytic procedure has been developed for the aerobic oxidative dehydrogenation of N-heterocycles by cobalt porphyrin in the absence of any additives. The catalytic system could tolerate various 1,2,3,4-tetrahydroquinoline derivatives and some other N-heterocycles. The corresponding N-heteroaromatics could be obtained in 59–86% yields. The mechanism investigation suggested that the aerobic oxidative dehydrogenation might proceed with imine intermediate through radical paths.
- Zhou, Weiyou,Chen, Dongwei,Sun, Fu'an,Qian, Junfeng,He, Mingyang,Chen, Qun
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supporting information
p. 949 - 953
(2018/02/09)
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- Vanadium-Catalyzed Dehydrogenation of N-Heterocycles in Water
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In this paper, the dehydrogenation of tetrahydroquinolines using oxovanadium(V) catalysts under mild conditions in water and oxygen atmosphere is described. This catalytic technology was successfully applied to a range of other structurally related N-heterocycles, and a reaction mechanism is proposed.
- Zumbr?gel, Nadine,Sako, Makoto,Takizawa, Shinobu,Sasai, Hiroaki,Gr?ger, Harald
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supporting information
p. 4723 - 4727
(2018/08/23)
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- Molybdenum-Catalyzed Deoxygenation of Heteroaromatic N-Oxides and Hydroxides using Pinacol as Reducing Agent
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A molybdenum-catalyzed deoxygenation of pyridine N-oxides and N-hydroxybenzotriazoles, as well as other azole N-oxides, has been developed using pinacol as an environmentally friendly oxo-acceptor. The only by-products are acetone and water making the process a convenient alternative to established protocols in terms of waste generation. The reaction is highly chemoselective and a variety of functional groups are tolerated. The processes are usually very clean allowing the isolation of the pure deoxygenated products after a simple extraction in most cases. (Figure presented.).
- Rubio-Presa, Rubén,Fernández-Rodríguez, Manuel A.,Pedrosa, María R.,Arnáiz, Francisco J.,Sanz, Roberto
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supporting information
p. 1752 - 1757
(2017/05/22)
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- Assembly of Diversely Substituted Quinolines via Aerobic Oxidative Aromatization from Simple Alcohols and Anilines
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An aerobic oxidative aromatization of simple aliphatic alcohols and anilines under the Pd(OAc)2/2,4,6-Collidine/Br?nsted acid catalytic system has been established, providing a direct approach for the preparation of diverse substituted quinoline derivatives in high yields with wide functional group tolerance. Practically, the protocol can be easily scaled up to gram-scale and was utilized in the concise formal synthesis of a promising herbicide candidate.
- Li, Jixing,Zhang, Jinlong,Yang, Huameng,Jiang, Gaoxi
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supporting information
p. 3284 - 3290
(2017/03/23)
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- Preparation method of quinoline derivative
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The invention provides a preparation method of a quinoline derivative. The method includes the steps of: in the presence of an oxidizing agent, adding a catalyst, then adding aniline or aromatic amine with different substituents, at the same time adding alcohol for reaction so as to prepare the quinoline derivative by one step. Specifically, the catalyst comprises a metal catalyst, an assistant catalyst I and an assistant catalyst II; the metal catalyst is a transition metal catalyst; the assistant catalyst I is an alkaline nitrogen-containing ligand; and the assistant catalyst II is an acidic compound. The quinoline derivative prepared by the method provided by the invention has stable performance and high purity. And the preparation method of the quinoline derivative can prepare quinoline, 2-methylquinoline, 8-hydroxyquinoline quinoline and other derivatives by one-step reaction, and the preparation method is simple and practicable. The preparation process does not produce new "three wastes", is environment-friendly, and provides a green and environment-friendly synthesis method. The preparation method has the characteristics of few raw material variety, little reaction equipment, few preparation step and low cost, and is more suitable for industrial production.
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Paragraph 0107; 0108
(2017/06/02)
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- Regioselective bromination: Synthesis of brominated methoxyquinolines
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Simple synthetic methods are described for the synthesis of valuable polyfunctional brominated methoxyquinolines 10–13, 20–21, and 24–25. Three regioselective routes are described for convenient preparation of brominated methoxyquinolines at the C-2, C-3,
- ?akmak, Osman,?kten, Salih
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p. 5389 - 5396
(2017/08/11)
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- Continuous niobium phosphate catalysed Skraup reaction for quinoline synthesis from solketal
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Solketal is derived from the reaction of acetone with glycerol, a by-product of the biodiesel industry. We report here the continuous reaction of solketal with anilines over a solid acid niobium phosphate (NbP), for the continuous generation of quinolines in the well-established Skraup reaction. This study shows that NbP can catalyse all the stages of this multistep reaction at 250 °C and 10 MPa pressure, with a selectivity for quinoline of up to 60%. We found that the catalyst eventually deactivates, most probably via a combination of coking and reduction processes but nevertheless we show the promise of this approach. We demonstrate here the application of our approach to synthesize both mono- and bis-quinolines from the commodity chemical, 4,4′-methylenedianiline.
- Jin, Jing,Guidi, Sandro,Abada, Zahra,Amara, Zacharias,Selva, Maurizio,George, Michael W.,Poliakoff, Martyn
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supporting information
p. 2439 - 2447
(2017/07/17)
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- Method for preparing quinoline derivative by catalyzing oxidative dehydrogenation of nitrogen-containing heterocyclic ring through carbon nitride material
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The invention belongs to the field of chemical synthesis, and particularly relates to a method for preparing a quinoline derivative by catalyzing oxidative dehydrogenation of a nitrogen-containing heterocyclic ring through a carbon nitride material. The carbon nitride material is prepared by using a nitrogen-containing organic macrocyclic compound as a precursor and calcining in an inert atmosphere. During a reaction, oxygen or air is used as an oxidant, and in the presence or absence of a solvent, the reaction is performed at 50-120 DEG C and the carbon nitrogen material can convert the nitrogen-containing heterocyclic ring into the corresponding quinoline derivative. According to the invention, no metal is introduced into a reaction system, and the method is easy to amplify; after being recycled for at least 9 times, a catalyst still maintain good selectivity and activity; therefore, the method has a significant practical prospect during industrial production.
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Paragraph 0012; 0013
(2017/08/29)
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- Organo-Photoredox Catalyzed Oxidative Dehydrogenation of N-Heterocycles
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We report here for the first time the catalytic oxidative dehydrogenation of N-heterocycles by a visible-light organo-photoredox catalyst with low catalyst loading (0.1–1 mol %). The reaction proceeds efficiently under base- and additive-free conditions with ambient air at room temperature. The utility of this benign approach is demonstrated by the synthesis of various pharmaceutically relevant N-heteroarenes such as quinoline, quinoxaline, quinazoline, acridine, and indole.
- Sahoo, Manoj K.,Jaiswal, Garima,Rana, Jagannath,Balaraman, Ekambaram
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supporting information
p. 14167 - 14172
(2017/10/16)
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- Heterogeneous mesoporous manganese oxide catalyst for aerobic and additive-free oxidative aromatization of N-heterocycles
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Herein, we report a heterogeneous, aerobic, additive-free and environmentally benign catalytic protocol for oxidative aromatization of saturated nitrogen-heterocycles using a mesoporous manganese oxide material. The aromatized products can be separated by easy filtration and the catalyst is reusable for at least four cycles. Mechanistic investigation provides evidence for radical intermediates, a multi-electron redox cycle between Mn centers, and an oxygen exchange mechanism.
- Mullick, Kankana,Biswas, Sourav,Angeles-Boza, Alfredo M.,Suib, Steven L.
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supporting information
p. 2256 - 2259
(2017/02/23)
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- Method for catalyzing nitrogen heterocyclic ring compound for oxidative dehydrogenation with hydrotalcite-like material
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The invention relates to a method for catalyzing a nitrogen heterocyclic ring compound for oxidative dehydrogenation with a hydrotalcite-like material, and belongs to the application aspect of a hydrotalcite-like component. The hydrotalcite-like component can be expressed as: A-MxM-LDHs (A=OH or CO3; M=Ni, Co, Cu, Mg or Zn; M=Fe, Mn, Al; M/M=(2 to 4)). Under existence of the catalyst and without adding any additives, oxidative dehydrogenation reaction is performed on the heterocyclic ring compound under a mild condition to prepare a corresponding aromatic compound. According to the method provided by the invention, the hydrotalcite-like material is based on non-noble metal, can be synthesized largely, and can be recycled; the method has the advantages of being high in catalytic reaction efficiency, mild in reaction condition, low in cost, easy to industrialize and the like.
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Paragraph 0048; 0049; 0050; 0051; 0053
(2017/10/27)
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- Palladium Nanoparticles Stabilized by Metal–Carbon Covalent Bonds as an Expeditious Catalyst for the Oxidative Dehydrogenation of Nitrogen Heterocycles
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The first method for the dehydrogenation of nitrogen heterocycles catalyzed by a palladium nanocatalyst was developed. Carbon–metal covalent-bond-stabilized nanoparticles were found to be efficient for the dehydrogenation process in the presence of tert-butyl hydroperoxide. A variety of N-heterocycles were transformed into functionalized quinolines in medium to excellent yields in water as the solvent under mild conditions by a simple operation.
- Sun, Xiao-Tao,Zhu, Jie,Xia, Yun-Tao,Wu, Lei
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p. 2463 - 2466
(2017/07/12)
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- MAGNETICALLY SEPARABLE IRON-BASED HETEROGENEOUS CATALYSTS FOR DEHYDROGENATION OF ALCOHOLS AND AMINES
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The present invention discloses an iron-based nitrogen doped graphene catalyst, process for preparation thereof and use of said catalyst in oxidant-free catalytic dehydrogenation of alcohols and amines to the corresponding carbonyl compounds, amines and N-heterocylic compounds with extraction of molecular hydrogen as the only by-product.
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Page/Page column 19; 20; 21; 23
(2016/12/22)
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- Highly Enantioselective Direct Synthesis of Endocyclic Vicinal Diamines through Chiral Ru(diamine)-Catalyzed Hydrogenation of 2,2′-Bisquinoline Derivatives
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An asymmetric hydrogenation of 2,2′-bisquinoline and bisquinoxaline derivatives, catalyzed by chiral cationic ruthenium diamine complexes, was developed. A broad range of chiral endocyclic vicinal diamines were obtained in high yields with excellent diastereo- and enantioselectivity (up to 93:7 dl/meso and >99 % ee). These chiral diamines could be easily transformed into a new class of chiral N-heterocyclic carbenes (NHCs), which are important but difficult to access.
- Ma, Wenpeng,Zhang, Jianwei,Xu, Cong,Chen, Fei,He, Yan-Mei,Fan, Qing-Hua
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supporting information
p. 12891 - 12894
(2016/10/04)
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- 6-methoxy quinoline synthesis method
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The invention relates to the technical field of pharmaceutical chemical industry and discloses a method for synthetizing 6-methoxyquinoline. The method comprises the following steps: (1) in terms of molar ratio, adding 4.3-4.5 parts of glycerol, 0.50-0.54 part of p-methoxy nitrobenzene, 0.20-0.25 part of ferrous sulfate and 1.0-1.3 parts of boric acid into 1 part of p-methoxyaniline and slowly dropwise adding concentrated sulfuric acid; (2) adding the concentrated sulfuric acid, heating to 140 DEG C and back flowing for 8-8.5 hours; (3) naturally cooling to room temperature and neutralizing a reaction liquid by using a sodium hydroxide solution till the pH is 5.5; (4) removing upwards-floating resin by using a pouring method, carrying out suction filtration, washing solid by using distilled water, washing the solid again by using ethyl acetate after the distilled water is pumped out, combining organic phases, extracting water phase by using the ethyl acetate and combining all the organic phases; and (5) removing the ethyl acetate through reduced pressure distillation, thereby obtaining the 6-methoxyquinoline. The method disclosed by the invention has the beneficial effects that inhibitors i.e. the ferrous sulfate and the boric acid are added, so that the reaction is effectively prevented from being too intense and the yield is increased; the whole process is simple in operation; and the raw materials are easy to get.
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Paragraph 0018; 0019
(2017/03/24)
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- Cu-Catalyzed Aerobic Oxidation of Di-tert-butyl Hydrazodicarboxylate to Di-tert-butyl Azodicarboxylate and Its Application on Dehydrogenation of 1,2,3,4-Tetrahydroquinolines under Mild Conditions
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A new class of co-catalytic system was developed with homogeneous CuI and di-tert-butyl azodicarboxylate for aerobic dehydrogenation of 1,2,3,4-tetrahydroquinolines under mild conditions. The developed co-catalytic system is consisting of di-tert-butyl azodicarboxylate-mediated dehydrogenation of 1,2,3,4-tetrahydroquinoline and aerobic oxidative regeneration of di-tert-butyl azodicarboxylate from di-tert-butyl hydrazodicarboxylate using molecular oxygen as a terminal oxidant. A variety of quinolines were efficiently synthesized by the developed Cu and di-tert-butyl azodicarboxylate co-catalytic system.
- Jung, Dahyeon,Kim, Min Hye,Kim, Jinho
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supporting information
p. 6300 - 6303
(2016/12/23)
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