- Microwaves under pressure for the continuous production of quinoline from glycerol
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Abstract Microwave heating is an interesting technology for chemical engineering, since it can provide effective volumetric heating of the reaction medium and reduce energy costs. Many commercially available laboratory-scale microwave reactors have already been used to carry out chemical reactions on a small scale (a few milliliters), and at high temperatures and pressures. Some research has been undertaken to scale-up microwave processes and make them suitable for a larger scale production. Indeed, combining wave propagation through the walls of a reactor with resistance toward high pressure and temperature as well, is not an easy task. For these reasons, this work focuses on the development of a pilot scale microwave apparatus used for the heating of larger reaction volumes under pressure, and under controlled conditions. The specially designed microwave apparatus allows chemical reactions in batch or continuous mode. The applicator operates in single mode enabling a uniform electromagnetic field, and well controlled operating conditions. The main advantage of the setup is the quite large reactor volume that permits either relatively long residence times or relatively high mass flowrates (up to 1 kg/h). The developed microwave apparatus was then used for quinoline synthesis from glycerol via a modified Skraup reaction. The major advantage of our system is the ability to carry out continuous chemical synthesis, at a large pilot scale, and high temperatures (200-220 °C), while ensuring a better control of the pressure (max. 19 bar) through the control of the power absorbed by the reaction medium.
- Saggadi,Polaert,Luart,Len,Estel
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- Reversible dehydrogenation-hydrogenation of tetrahydroquinoline-quinoline using a supported copper nanoparticle catalyst
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Copper nanoparticles synthesized on a titania surface (Cu/TiO2) act as an efficient heterogeneous catalyst for the reversible dehydrogenation and hydrogenation of tetrahydroquinoline-quinoline under an atmospheric pressure of H2. The Japan Institute of Heterocyclic Chemistry.
- Mikami, Yusuke,Ebata, Kaori,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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- Copper-Catalyzed Direct Oxidative α-Functionalization of Tetrahydroquinoline in Water under Mild Conditions
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An efficient one-step α-functionalization of tetrahydroquinoline under mild conditions is achieved. The direct oxidative copper-catalyzed dehydrogenative cross C(sp3)?C(sp2) couplings of tetrahydroquinolines and indoles produced the products in aqueous and open air medium. The use of inexpensive copper catalyst, water solvent, easy to operate open air condition combined with the most step and atom economic features qualify the CDC reaction for a green process. (Figure presented.).
- Ramana, Daggupati V.,Chandrasekharam, Malapaka
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- Copper(ii)/amine synergistically catalyzed enantioselective alkylation of cyclic N-acyl hemiaminals with aldehydes
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The first catalytic asymmetric alkylation of N-acyl quinoliniums with aldehydes has been described. A copper/amine synergistic catalytic system has been developed, allowing the addition of functionalized aldehydes to a wide range of electronically varied N-acyl quinoliniums in good yields with excellent enantiocontrol. The synergistic catalytic system was also effective for N-acyl dihydroisoquinoliniums and β-caboliniums, demonstrating the general applicability of the protocol in the enantioselective alkylation of diverse cyclic N-acyl hemiaminals. This journal is
- Sun, Shutao,Mao, Ying,Lou, Hongxiang,Liu, Lei
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- A Novel Gemini Sulfonic Ionic Liquid Immobilized MCM-41 as Efficient Catalyst for Doebner-Von Miller Reaction to Quinoline
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A novel 2,2′-bipyridine-based gemini sulfonic ionic liquid was first synthesized and then immobilized on MCM-41 support (named IL1/MCM-41), which was further characterized using XRD, FT-IR, SEM, TEM, N2-physisorption, XPS and TG techniques. These characterization results revealed that the IL1/MCM-41 presented a whole ordered mesoporous structure, excellent thermal stability as well as the interaction between ionic liquid with MCM-41. Catalytic activity of the obtained IL1/MCM-41 was systematically evaluated for the Doebner-Von Miller reaction to generate quinoline. Compared to conventional imidazole-type single sulfonic ionic liquid supported on MCM-41 (named IL2/MCM-41), IL1/MCM-41 exhibited higher catalytic activity and better reusability, which was probably due to the synergistic catalytic effect of the dual sulfonic acid group on IL2 and the stronger interaction between dipyridine ring of ionic liquid with MCM-41 support, respectively. Meanwhile, a plausible reaction routes for the synergistic catalytic action of dual sulfonic acid to quinoline over the IL1/MCM-41 catalyst was also proposed in this paper.
- Li, An,Wang, Xinyang,Li, Yuhang,Luo, Caiwu,Zhang, Jiance,Liu, Kun,Zhang, Cen,Zhou, Congshan
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- Zn-promoted Hβ zeolite for gas-phase catalyzed aza-heterocyclic-aromatization of acrolein dimethyl acetal and aniline to quinolines
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Catalytic activities of Zn-promoted Hβ zeolite for gas-phase aza-heterocyclic-aromatization of acrolein dimethyl acetal and aniline to quinolines were investigated. the Zn/Hβ catalyst showed better selectivity to quinoline than the parent Hβ one. Characterization results demonstrated that the Zn/Hβ catalyst prepared via deposition precipitation method existed the isolated Zn2+ cations as well as the highly dispersed ZnO clusters, which not only decreased concentration of strong acid sites but also enhanced enhance aromatization process. As a result, the decrease of strong acid sites restrained the cracking of acrolein to acetaldehyde as well as the alkylation of quinoline to ethylquinoline effectively; and the Zn species of catalyst further improved aromatization process of dihydroquinoline to quinoline. Moreover, the Zn/Hβ catalyst presented relatively enhanced ability of anti-activation and excellent regenerability, owing to decrease strong acid-induced polymerization of active intermediates to form the coking. Under the optimized operating conditions, more than 51 % yield of quinoline was achieved over Zn/Hβ catalyst; which far exceeded quinoline yield (28 %) over the pure Hβ one. Besides, a plausible reaction routes in vapor-phase acrolein diethyl acetal with aniline to quinolines were suggested in this paper.
- Li, An,Li, Lijun,Lin, Ying,Liu, Kun,Liu, Yong,Luo, Caiwu,Zhou, Congshan
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- Mesoporous HBeta zeolite obtained: Via zeolitic dissolution-recrystallization successive treatment for vapor-phase Doebner-Von Miller reaction to quinolines
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A reassembled HBeta zeolite (HBeta-Ct) was obtained via zeolitic dissolution-recrystallization successive treatment, and characterized by means of XRD, FT-IR, SEM, TEM, N2 adsorption-desorption as well as NH3-TPD techniques. The characterization results manifested that the HBeta-Ct zeolite possessed more mesopores and less acid than the parent one. Catalyst activities of the parent and reassembled HBeta catalysts were investigated in detail in the vapor-phase Doebner-Von Miller reaction to quinolines. The results demonstrated that the reassembled HBeta zeolite showed enhanced catalyst stability and improved anti-alkylation ability. This is probably due to the existence of mesopores on the catalyst which strengthened the diffusion of bulky products from pore channels in the zeolite. Meanwhile, the decreased acid amount over the catalyst can also retard the alkylation process to generate alkylquinolines as well as the acid-induced polymerization reaction to form coke. Besides, the HBeta-Ct catalyst also exhibited good regenerability in the Doebner-Von Miller reaction. This journal is
- Li, An,Luo, CaiWu,Wu, Fen,Zheng, ShuQin,Li, LiJun,Zhang, JianCe,Chen, Liang,Liu, Kun,Zhou, Congshan
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- Bioinspired Atomic Manganese Site Accelerates Oxo-Dehydrogenation of N-Heterocycles over a Conjugated Tri- s-Triazine Framework
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Herein, taking inspirations from metalloenzymes, we constructed atomically dispersed manganese sites anchored onto conjugated tri-s-triazine units of graphitic carbon nitride as a bioinspired photocatalyst (Mn1/tri-CN) for the oxo-dehydrogenation of N-heterocycles. The primary coordination sphere of atomic Mn-N2 sites (role i: oxygen activation) as well as the π-πstacking interactions between tri-s-triazine units and substrate mimicking the secondary coordination sphere (role ii: substrate adsorption) synergistically realized high-efficiency electron transfer/utilization in photocatalytic oxidation reactions, as was demonstrated experimentally and theoretically. The Mn1/tri-CN catalyst exhibited impressive oxo-dehydrogenation activity and selectivity toward a broad scope of N-heterocycles in an air atmosphere. The current work suggests that simultaneously engineering the metal active sites of catalysts and the adaptive local environment of the matrix may open an avenue for the synthesis of fine chemicals.
- Zhang, Zhou,Liu, Wengang,Zhang, Yuanyuan,Bai, Jingwen,Liu, Jian
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- A biomass-derived N-doped porous carbon catalyst for the aerobic dehydrogenation of nitrogen heterocycles
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N-doped porous carbon (NC) was synthesized from sugar cane bagasse, which is a sustainable and widely available biomass waste. The preferred NC sample had a well-developed porous structure, a graphene-like surface morphology and different N species. More
- Cui, Fu-Jun,Guo, Fu-Hu,Liu, Jing-Jiang,Liu, Xiao-Yu,Quan, Zheng-Jun,Ullah, Arif,Wang, Xi-Cun,Zhu, Ji-Hua
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supporting information
p. 1791 - 1799
(2022/01/31)
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- Dehydrogenation of N-Heterocyclic Compounds Using H2O2 and Mediated by Polar Solvents
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The oxidative dehydrogenation of N-heterocyclic compounds by using H2O2 as oxidant in combination with polar solvents such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and H2O is described. Among these two solvents, the best yields for the heteroaromatic compounds were generally achieved in HFIP. However, it is remarkable, that the use of a non toxic solvent such as H2O gave such good yields. Furthermore, the procedure was implemented in larger-scale and HFIP was distilled from the reaction mixture and reused (up to 5 cycles) without a significant detriment in the reaction outcome. (Figure presented.).
- Llopis, Natalia,Gisbert, Patricia,Baeza, Alejandro,Correa-Campillo, Jara
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supporting information
p. 1205 - 1210
(2022/02/25)
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- Solvothermal fabrication of Bi2MoO6 nanocrystals with tunable oxygen vacancies and excellent photocatalytic oxidation performance in quinoline production and antibiotics degradation
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Novel Bi2MoO6 nanocrystals with tunable oxygen vacancies have been developed via a facile low-cost approach with the assistance of a glyoxal reductant under solvothermal conditions. With the introduction of oxygen vacancies, the optical absorption of Bi2MoO6 is extended and its bandgap narrowed. Oxygen vacancies not only lead to the appearance of a defect band level in the forbidden band but can also result in a minor up-shift of the valence band maximum, promoting the mobility of photogenerated holes. Moreover, oxygen vacancies can act as electron acceptors, temporarily capturing electrons excited by light and reducing the recombination of electrons and holes. At the same time, oxygen vacancies help to capture oxygen, which reacts with the captured photogenerated electrons to generate more superoxide radicals (?O2?) to participate in the reaction, thereby significantly promoting the redox performance of the photocatalyst. From Bi2MoO6 containing these oxygen vacancies (OVBMO), excellent photocatalytic performance has been obtained for the oxidation of 1,2,3,4-tetrahydroquinoline to produce quinoline and cause antibiotic degradation. The reaction mechanism of the oxidation of 1,2,3,4-tetrahydroquinoline to quinoline over the OVBMO materials is elucidated in terms of heterogeneous Catal. via a radical pathway.
- Fan, Qizhe,Liu, Xingqiang,Liu, Zhen,Tian, Jian,Yu, Changlin
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p. 472 - 484
(2022/01/22)
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- Palladium-catalyzed aryl group transfer from triarylphosphines to arylboronic acids
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A study of Pd-catalyzed arylation of arylboronic acids with triarylphosphines is presented. Various parameters of this transformation, such as the oxygen presence, choice of solvent, temperature, palladium source, bases and oxidants, were tested and the optimal conditions of the aryl transfer were determined. The effect of electron-withdrawing and electron-donating substituents on the aryl groups of both reactants was also investigated. The unusual transfer of the acetate group from Pd(OAc)2 to p-nitrophenylboronic acid in the presence of PAr3 is reported. A plausible mechanism of the Pd-catalyzed aryl group transfer from PAr3 to the arylboronic acid is proposed.
- Enright, Dale R.,Gogate, Akash R.,Smoliakova, Irina P.,Vasireddy, Purna C. R.
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- Method for preparing 3 - arylquinoline
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The invention discloses a method for preparing 3 - arylquinoline, which is carried out in an oxygen-containing atmosphere, ortho-amine arylmethanol and aryl formaldehyde in DMSO-solution system containing an alkali to obtain 3 -arylquinoline compounds. In 3 - arylquinoline compound structure prepared by the method, 2 carbon atoms are provided by DMSO, aryl groups at 3 carbon atoms and 3 positions are provided by aryl formaldehyde, and all other atoms in the quinoline compound structure are provided by raw material o-amido aryl methanol. The method for synthesizing 3 - arylquinoline has the advantages of wide raw material sources, environmental friendliness, low price and simple operation, and is beneficial to industrial production.
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Paragraph 0047; 0048; 0051; 0053; 0054; 0132-0134
(2021/11/26)
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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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- Heterogeneous Hydrogenation of Quinoline Derivatives Effected by a Granular Cobalt Catalyst
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We communicate a convenient method for the pressure hydrogenation of quinolines in aqueous solution by using a particulate cobalt-based catalyst that is prepared in situ from simple Co(OAc)2 4H2O through reduction with abundant zinc powder. This catalytic protocol permits a brisk and atom-efficient access to a variety of 1,2,3,4-tetrahydroquinolines thereby relying solely on easy-to-handle reagents that are all readily obtained from commercial sources. Both the reaction setup assembly and the autoclave charging procedure are conducted on the bench outside an inert-gas-operated containment system, thus rendering the overall synthesis time-saving and operationally very simple.
- Timelthaler, Daniel,Topf, Christoph
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- Metal–Organic Layers Hierarchically Integrate Three Synergistic Active Sites for Tandem Catalysis
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We report the design of a bifunctional metal–organic layer (MOL), Hf12-Ru-Co, composed of [Ru(DBB)(bpy)2]2+ [DBB-Ru, DBB=4,4′-di(4-benzoato)-2,2′-bipyridine; bpy=2,2′-bipyridine] connecting ligand as a photosensitizer and Co(dmgH)2(PPA)Cl (PPA-Co, dmgH=dimethylglyoxime; PPA=4-pyridinepropionic acid) on the Hf12 secondary building unit (SBU) as a hydrogen-transfer catalyst. Hf12-Ru-Co efficiently catalyzed acceptorless dehydrogenation of indolines and tetrahydroquinolines to afford indoles and quinolones. We extended this strategy to prepare Hf12-Ru-Co-OTf MOL with a [Ru(DBB)(bpy)2]2+ photosensitizer and Hf12 SBU capped with triflate as strong Lewis acids and PPA-Co as a hydrogen transfer catalyst. With three synergistic active sites, Hf12-Ru-Co-OTf competently catalyzed dehydrogenative tandem transformations of indolines with alkenes or aldehydes to afford 3-alkylindoles and bisindolylmethanes with turnover numbers of up to 500 and 460, respectively, illustrating the potential use of MOLs in constructing novel multifunctional heterogeneous catalysts.
- Quan, Yangjian,Lan, Guangxu,Shi, Wenjie,Xu, Ziwan,Fan, Yingjie,You, Eric,Jiang, Xiaomin,Wang, Cheng,Lin, Wenbin
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supporting information
p. 3115 - 3120
(2020/12/09)
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- Iron-Catalyzed ?±,?-Dehydrogenation of Carbonyl Compounds
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An iron-catalyzed α,β-dehydrogenation of carbonyl compounds was developed. A broad spectrum of carbonyls or analogues, such as aldehyde, ketone, lactone, lactam, amine, and alcohol, could be converted to their α,β-unsaturated counterparts in a simple one-step reaction with high yields.
- Zhang, Xiao-Wei,Jiang, Guo-Qing,Lei, Shu-Hui,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 1611 - 1615
(2021/03/03)
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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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supporting information
p. 431 - 437
(2021/01/11)
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- Highly Ordered Mesoporous Cobalt Oxide as Heterogeneous Catalyst for Aerobic Oxidative Aromatization of N-Heterocycles
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N-heterocycles are key structures for many pharmaceutical intermediates. The synthesis of such units normally is conducted under homogeneous catalytic conditions. Among all methods, aerobic oxidative aromatization is one of the most effective. However, in homogeneous conditions, catalysts are difficult to be recycled. Herein, we report a heterogeneous catalytic strategy with a mesoporous cobalt oxide as catalyst. The developed protocol shows a broad applicability for the synthesis of N-heterocycles (32 examples, up to 99 % yield), and the catalyst presents high turnover numbers (7.41) in the absence of any additives. Such a heterogenous approach can be easily scaled up. Furthermore, the catalyst can be recycled by simply filtration and be reused for at least six times without obvious deactivation. Comparative studies reveal that the high surface area of mesoporous cobalt oxide plays an important role on the catalytic reactivity. The outstanding recycling capacity makes the catalyst industrially practical and sustainable for the synthesis of diverse N-heterocycles.
- Cao, Yue,Wu, Yong,Zhang, Yuanteng,Zhou, Jing,Xiao, Wei,Gu, Dong
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p. 3679 - 3686
(2021/06/18)
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- Electro-Descriptors for the Performance Prediction of Electro-Organic Synthesis
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Electrochemical organic synthesis has attracted increasing attentions as a sustainable and versatile synthetic platform. Quantitative assessment of the electro-organic reactions, including reaction thermodynamics, electro-kinetics, and coupled chemical pr
- Chen, Yuxuan,Tian, Bailin,Cheng, Zheng,Li, Xiaoshan,Huang, Min,Sun, Yuxia,Liu, Shuai,Cheng, Xu,Li, Shuhua,Ding, Mengning
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supporting information
p. 4199 - 4207
(2020/12/25)
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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 organoboron-catalysed metal-free dehydrogenation of N-heterocycles using molecular oxygen
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The surge of photocatalytic transformation not only provides unprecedented synthetic methods, but also triggers the enthusiasm for more sustainable photocatalysts. On the other hand, oxygen is an ideal oxidant in terms of atom economy and environmental friendliness. However, the poor reactivity of oxygen at the ground state makes its utilization challenging. Herein, a visible-light-induced oxidative dehydrogenative process is disclosed, which uses an organoboron compound as the photocatalyst and molecular oxygen as the sole oxidant.Viathis approach, an array of N-heterocycles have been accessed under metal-free mild conditions, in good to excellent yields.
- Wei, Lanfeng,Wei, Yu,Xu, Liang,Zhang, Jinli
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supporting information
p. 4446 - 4450
(2021/06/30)
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- Ruthenium-Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism
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The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox-active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system.
- Huang, Lin,Bismuto, Alessandro,Rath, Simon A.,Trapp, Nils,Morandi, Bill
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supporting information
p. 7290 - 7296
(2021/03/01)
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- Semi-Rational Engineering of Toluene Dioxygenase from Pseudomonas putida F1 towards Oxyfunctionalization of Bicyclic Aromatics
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Toluene dioxygenase (TDO) from Pseudomonas putida F1 was engineered towards the oxyfunctionalization of bicyclic substrates. Single and double mutant libraries addressing 27 different positions, located at the active site and entrance channel were generated. In total, 176 different variants were tested employing the substrates naphthalene, 1,2,3,4-tetrahydroquinoline, and 2-phenylpyridine. Introduced mutations in positions M220, A223 and F366, exhibited major influences in terms of product formation, chemo-, regio- and enantioselectivity. By semi-rational evolution, we lighted up the TDO capability to convert bulkier substrates than its natural substrate, at unprecedented reported conversions. Thus, the most active TDO variants were applied to biocatalytic oxyfunctionalizations of 1,2,3,4-tetrahydroquinoline, and 2-phenylpyridine, enabling the production of substantial amounts of (+)-(R)-1,2,3,4-tetrahydroquinoline-4-ol (71% isolated yield, 94% ee) and (+)-(1S,2R)-3-(pyridin-2-yl)cyclohexa-3,5-diene-1,2-diol (60% isolated yield, 98% ee), respectively. Here, we provide a set of novel TDO-based biocatalysts useful for the preparation of oxyfunctionalized bicyclic scaffolds, which are valuable to perform downstream synthetic processes. (Figure presented.).
- Wissner, Julian L.,Schelle, Jona T.,Escobedo-Hinojosa, Wendy,Vogel, Andreas,Hauer, Bernhard
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p. 4905 - 4914
(2021/05/05)
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- Cyclometalated Half-Sandwich Iridium(III) Complexes: Synthesis, Structure, and Diverse Catalytic Activity in Imine Synthesis Using Air as the Oxidant
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Four air-stable cyclometalated half-sandwich iridium complexes 1-4 with C,N-donor Schiff base ligands were prepared through C-H activation in moderate-to-good yields. These complexes have been well characterized, and their exact structure was elaborated on by single-crystal X-ray analysis. The iridium(III) complexes 1-4 showed good catalytic activity in the imine synthesis under open-flask conditions (air as the oxidant) from primary amine oxidative homocoupling, secondary amine dehydrogenation, and the cross-coupling reaction of amine and alcohol. Substituents bonded on the ligands of the iridium complexes displayed little effect on the catalytic efficiency. The stability and good catalytic efficiency of the iridium catalysts, mild reaction conditions, and substrate universality showed their potential application in industrial production.
- Li, Rong-Jian,Ling, Chun,Lv, Wen-Rui,Deng, Wei,Yao, Zi-Jian
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p. 5153 - 5162
(2021/05/04)
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- Manganese(III) Acetate Catalyzed Aerobic Dehydrogenation of Tertiary Indolines, Tetrahydroquinolines and an N-Unsubstituted Indoline
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A Mn(OAc)3 ? 2H2O-catalyzed aerobic dehydrogenation of five and six-membered N-heterocycles for the synthesis of N-heteroarenes is reported. Of note, this protocol can be applied to the dehydrogenation of tertiary indolines with various electron-deficient N-substituents. Preliminary mechanistic investigations support that a single-electron transfer pathway might be involved. (Figure presented.).
- Niu, Xiaokang,Yang, Lei
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supporting information
p. 4209 - 4215
(2021/08/06)
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- Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant
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A nickel-catalyzed reductive decyanation of aromatic nitriles has been developed, in which the readily available and abundant ethanol was applied as the hydride donor. Various functional groups on the aromatic rings, such as alkoxyl, amino, imino and amide, were compatible in this catalytic protocol. Heteroaryl, benzylic and alkenyl nitriles were also tolerated. Mechanistic investigation indicated that ethanol provided hydride efficientlyviaβ-hydride elimination in this reductive decyanation.
- Wu, Ke,Ling, Yichen,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Jin, Liqun,Hu, Xinquan
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supporting information
p. 2273 - 2276
(2021/03/09)
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- Unexpected Annulation between 2-Aminobenzyl Alcohols and Benzaldehydes in the Presence of DMSO: Regioselective Synthesis of Substituted Quinolines
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An unexpected annulation among 2-aminobenzyl alcohols, benzaldehydes, and DMSO to quinolines has been disclosed. For the reported annulation between 2-aminobenzyl alcohols and benzaldehydes, the change of the solvent from toluene to DMSO led to the change of the product from the diheteroatomic cyclic benzoxazines to monoheteroatomic cyclic quinolines. This annulation can be used to synthesize regioselectively different substituted quinolines by the choice of different 2-amino alcohols, aldehydes, and sulfoxides as substrates. Interestingly, introducing substituent groups to the α-position of sulfoxides resulted in the interchange of the positions between benzaldehydes and sulfoxides in the product quinolines. On the basis of the control experiments and literatures, a plausible mechanism for this annulation was proposed.
- Yang, Tonglin,Nie, Zhi-Wen,Su, Miao-Dong,Li, Hui,Luo, Wei-Ping,Liu, Qiang,Guo, Can-Cheng
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p. 15228 - 15241
(2021/10/25)
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- Acceptorless dehydrogenative condensation: synthesis of indoles and quinolines from diols and anilines
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The use of diols and anilines as reagents for the preparation of indoles represents a challenge in organic synthesis. By means of acceptorless dehydrogenative condensation, heterocycles, such as indoles, can be obtained. Herein we present an experimental and theoretical study for this purpose employing heterogeneous catalysts Pt/Al2O3and ZnO in combination with an acid catalyst (p-TSA) and NMP as solvent. Under our optimized conditions, the diol excess has been reduced down to 2 equivalents. This represents a major advance, and allows the use of other diols. 2,3-Butanediol or 1,2-cyclohexanediol has been employed affording 2,3-dimethyl indoles and tetrahydrocarbazoles. In addition, 1,3-propanediol has been employed to prepare quinolines or natural and synthetic julolidines.
- Bellezza, Delia,Zaragozá, Ramón J.,José Aurell,Ballesteros, Rafael,Ballesteros-Garrido, Rafael
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supporting information
p. 677 - 683
(2021/02/06)
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- Waste-minimized synthesis of C2 functionalized quinolines exploiting iron-catalysed C-H activation
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Herein we present an efficient and regioselective iron-catalyzed methodology for the external oxidant-free functionalization of quinoline-N-oxides. The protocol, based on the use of inexpensive and easily accessible FeSO4, showed broad applicability to a wide range of substrates. An additional green feature of this synthetic methodology is H2O being the only by-product. Experimental and computational investigations provide support to a mechanism based on a facile C-H activation event. The green efficiency of the process has also been carefully assessed using: (i) metrics related to the synthetic process (AE, Yield, 1/SF, MRP and RME); (ii) safety/hazard metrics (SHZI and SHI); and (iii) metrics related to the metal used as the catalyst (Abundance, OEL and ADP). In addition to the many advantages of this protocol related to the green iron catalyst used and the safety/hazard features of the process, an E-factor value of ca. 0.92 (84 to >99% reduction compared to known protocols) evidently confirms the sustainable efficiency of the procedure presented. Practical utility has also been demonstrated by performing the reaction efficiently on a multi-gram scale. This journal is
- Ferlin, Francesco,Zangarelli, Agnese,Lilli, Simone,Santoro, Stefano,Vaccaro, Luigi
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supporting information
p. 490 - 495
(2021/01/28)
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- Nickel-Catalyzed Hydrodeoxygenation of Aryl Sulfamates with Alcohols as Mild Reducing Agents
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The nickel-catalyzed hydrodeoxygenation of aryl sulfamates has been developed with alcohols as mild reductants. A variety of functional groups and heterocycles were tolerated in this reaction system to give the desired products in high yields. In addition, the gram-scale process and stepwise cine-substitution were also achieved with high efficiency.
- Matsuo, Kasumi,Kuriyama, Masami,Yamamoto, Kosuke,Demizu, Yosuke,Nishida, Koyo,Onomura, Osamu
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p. 4449 - 4460
(2021/08/25)
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- Heterogeneously Catalyzed Selective Decarbonylation of Aldehydes by CeO2-Supported Highly Dispersed Non-Electron-Rich Ni(0) Nanospecies
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Aldehyde decarbonylation has been extensively investigated, primarily using noble-metal catalysts; however, nonprecious-base-metal-catalyzed aldehyde decarbonylation has been hardly reported. We have established an efficient selective aldehyde decarbonylation reaction with a broad substrate scope and functional group tolerance utilizing a heterogeneous Ni(0) nanospecies catalyst supported on CeO2. The high catalytic performance is attributable to the highly dispersed and non-electron-rich Ni(0) nanospecies, which possibly suppress a side reaction producing esters and adsorbed CO-derived inhibition of the catalytic turnover, according to detailed catalyst characterization and kinetic evaluation.
- Matsuyama, Takehiro,Yatabe, Takafumi,Yabe, Tomohiro,Yamaguchi, Kazuya
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p. 13745 - 13751
(2021/11/17)
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- Catalytic Aldehyde and Alcohol Arylation Reactions Facilitated by a 1,5-Diaza-3,7-diphosphacyclooctane Ligand
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We report a catalytic method to access secondary alcohols by the coupling of aryl iodides. Either aldehydes or alcohols can be used as reaction partners, making the transformation reductive or redox-neutral, respectively. The reaction is mediated by a Ni catalyst and a 1,5-diaza-3,7-diphosphacyclooctane. This P2N2ligand, which has previously been unrecognized in cross-coupling and related reactions, was found to avoid deleterious aryl halide reduction pathways that dominate with more traditional phosphines and NHCs. An interrupted carbonyl-Heck type mechanism is proposed to be operative, with a key 1,2-insertion step forging the new C-C bond and forming a nickel alkoxide that may be turned over by an alcohol reductant. The same catalyst was also found to enable synthesis of ketone products from either aldehydes or alcohols, demonstrating control over the oxidation state of both the starting materials and products.
- Isbrandt, Eric S.,Nasim, Amrah,Newman, Stephen G.,Zhao, Karen
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supporting information
p. 14646 - 14656
(2021/09/18)
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- Ceramic boron carbonitrides for unlocking organic halides with visible light
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Photochemistry provides a sustainable pathway for organic transformations by inducing radical intermediates from substrates through electron transfer process. However, progress is limited by heterogeneous photocatalysts that are required to be efficient, stable, and inexpensive for long-term operation with easy recyclability and product separation. Here, we report that boron carbonitride (BCN) ceramics are such a system and can reduce organic halides, including (het)aryl and alkyl halides, with visible light irradiation. Cross-coupling of halides to afford new C-H, C-C, and C-S bonds can proceed at ambient reaction conditions. Hydrogen, (het)aryl, and sulfonyl groups were introduced into the arenes and heteroarenes at the designed positions by means of mesolytic C-X (carbon-halogen) bond cleavage in the absence of any metal-based catalysts or ligands. BCN can be used not only for half reactions, like reduction reactions with a sacrificial agent, but also redox reactions through oxidative and reductive interfacial electron transfer. The BCN photocatalyst shows tolerance to different substituents and conserved activity after five recycles. The apparent metal-free system opens new opportunities for a wide range of organic catalysts using light energy and sustainable materials, which are metal-free, inexpensive and stable. This journal is
- Yuan, Tao,Zheng, Meifang,Antonietti, Markus,Wang, Xinchen
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p. 6323 - 6332
(2021/05/19)
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- Synthesis of Pyridines and Quinolines by Heterogeneous Catalytic Condensation of Ammonia and Aniline with Glycerol and Its Isopropylidene Derivative
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Abstract: Synthesis of pyridines and quinolines by the condensation of ammonia and aniline with glycerol and its isopropylidene derivative on zeolite catalysts with micro- and micro-meso-macroporous structure has been studied for the first time. Effect of processing parameters (temperature, catalyst type, and initial reagent ratio) on product yield (pyridine and a mixture of o- and p-methylpyridines or quinoline and a mixture of o- and p-methylquinolines) has been studied.
- Bayburtli, A. V.,Grigorieva, N. G.,Kutepov, B. I.,Raskil’dina, G. Z.,Zlotsky, S. S.
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- A Mild Method for Electrochemical Reduction of Heterocyclic N-Oxides
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Deoxygenation of heteroaromatic N-oxides is commonly accomplished using chemical or enzymatic methods. In this work, we report on an expedient protocol for electrochemical reduction of pyridine N-oxide derivatives under mild conditions. A diverse range of mono- and bis N-oxides were converted into the corresponding nitrogen bases in good yields. Importantly, the method is highly selective towards N-oxides and tolerates challenging halo and nitro substituents in the heteroaromatic ring.
- Fukazawa, Yasuaki,Rubtsov, Aleksandr E.,Malkov, Andrei V.
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supporting information
p. 3317 - 3319
(2020/05/25)
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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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- Copper-Catalyzed ortho-Functionalization of Quinoline N-Oxides with Vinyl Arenes
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An efficient copper-catalyzed regioselective C?H alkenylation and borylative alkylation of quinoline N-oxides with vinyl arenes in the presence of pinacol diborane has been developed. The reaction proceeds through the borylcupration of the vinyl arenes followed by nucleophilic attack of the resulting alkyl copper species to the quinoline N-oxides. Benzoquinone and KOtBu were identified as the necessary additives at the second step of the reaction that are crucial for the success of the reaction. A wide range of C2-functionalizaed quinolines were obtained with good functional group tolerance, which may find utilities in pharmaceuticals and synthetic chemistry.
- Hu, Hui,Hu, Xiaoping,Liu, Yuanhong
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supporting information
p. 18975 - 18979
(2020/08/25)
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- Simple manganese carbonyl catalyzed hydrogenation of quinolines and imines
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Manganese-catalyzed hydrogenation of unsaturated molecules has made tremendous progresses recently benefiting from non-innocent pincer or bidentate ligands for manganese. Herein, we describe the hydrogenation of quinolines and imines catalyzed by simple manganese carbonyls, Mn2(CO)10 or MnBr(CO)5, thus eliminating the prerequisite pincer-type or bidentate ligands.
- Wang, Zelong,Chen, Lei,Mao, Guoliang,Wang, Congyang
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p. 1890 - 1894
(2020/03/04)
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- Experimental and computational evidence on gold-catalyzed regioselective hydration of phthalimido-protected propargylamines: An entry to β-amino ketones
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The results of our investigations on the Au-catalyzed regioselective hydration reaction of both alkyl- A nd aryl-substituted N-propargyl phthalimides directed to the selective formation of the corresponding β-phthalimido ketones are described. Experimental data, in particular the observed regioselectivity, have been qualitatively supported by quantum-chemical calculations carried out on model systems in the framework of Density Functional Theory (DFT) followed by quantum theory of atoms in molecules (QTAIMS). Our results suggest that the electronic features of the initial adduct between the propargyl triple bond and the Au(i) catalyst, in particular the character of the gold-triple bond interaction, are essential for the observed regioselectivity. Other effects, such as the presence of the solvent and the formation of a H-bond between the water molecule and the phthalimido moiety, although apparently irrelevant for the regioselectivity, have proven to be kinetically and catalytically rather important. This journal is
- Arcadi, Antonio,Aschi, Massimiliano,Marsicano, Vincenzo,Michelet, Véronique
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p. 9438 - 9447
(2020/12/15)
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- Metal–Organic Frameworks for the Exploitation of Distance between Active Sites in Efficient Photocatalysis
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Discoveries of the accurate spatial arrangement of active sites in biological systems and cooperation between them for high catalytic efficiency are two major events in biology. However, precise tuning of these aspects is largely missing in the design of artificial catalysts. Here, a series of metal–organic frameworks (MOFs) were used, not only to overcome the limit of distance between active sites in bio-systems, but also to unveil the critical role of this distance for efficient catalysis. A linear correlation was established between photocatalytic activity and the reciprocal of inter active-site distance; a smaller distance led to higher activity. Vacancies created at selected crystallographic positions of MOFs promoted their photocatalytic efficiency. MOF-525-J33 with 15.6 ? inter active-site distance and 33 % vacancies exhibited unprecedented high turnover frequency of 29.5 h?1 in visible-light-driven acceptorless dehydrogenation of tetrahydroquinoline at room temperature.
- Deng, Hexiang,Gong, Xuan,Jiang, Zhuo,Lu, Lingxiang,Shu, Yufei,Wang, Chao,Xu, Xiaohui
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supporting information
p. 5326 - 5331
(2020/02/18)
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- Nickel-Catalyzed Dehydrogenation of N-Heterocycles Using Molecular Oxygen
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Herein, an efficient and selective nickel-catalyzed dehydrogenation of five- and six-membered N-heterocycles is presented. The transformation occurs in the presence of alkyl, alkoxy, chloro, free hydroxyl and primary amine, internal and terminal olefin, trifluoromethyl, and ester functional groups. Synthesis of an important ligand and the antimalarial drug quinine is demonstrated. Mechanistic studies revealed that the cyclic imine serves as the key intermediate for this stepwise transformation.
- Banerjee, Debasis,Bera, Atanu,Bera, Sourajit
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supporting information
(2020/09/02)
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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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- MnOx/catechol/H2O: A cooperative catalytic system for aerobic oxidative dehydrogenation of N-heterocycles at room temperature
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Amorphous manganese oxide doped by Na+ ion (Na-AMO) was successfully prepared and found to be an efficient heterogeneous catalyst in aerobic oxidative dehydrogenation of N-heterocycles, cooperate with catechol. Na-AMO was fully characterized by XRD, XPS BET H2-TPR, CO2-TPD FT-IR, TEM, SEM and had rich amounts of surface absorbed active oxygen species which are responsible for superior catalytic performance. The synergistic interaction between Na-AMO and catechol makes catalytic system efficient and tolerant, which offers various N-heterocycles in good to excellent yields under mild conditions.
- Tang, Tao,Bi, Xiuru,Meng, Xu,Chen, Gexin,Gou, Mingxia,Liu, Xiang,Zhao, Peiqing
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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 0029-0036
(2020/11/12)
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- NCP-Type Pincer Iridium Complexes Catalyzed Transfer-Dehydrogenation of Alkanes and Heterocycles?
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A series of NCP-type pincer iridium complexes, (RNCCP)IrHCl (2a—2c) and (BQ-NCOP)IrHCl 3, have been studied for catalytic transfer alkane dehydrogenation. Complex 3 containing a rigid benzoquinoline backbone exhibits high activity and robustness in dehydrogenation of alkanes to form alkenes. Even more importantly, this catalyst system was also highly effective in the dehydrogenation of a wide range of heterocycles to furnish heteroarenes.
- Wang, Yulei,Qian, Lu,Huang, Zhidao,Liu, Guixia,Huang, Zheng
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supporting information
p. 837 - 841
(2020/05/18)
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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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- 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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- Development of Pd(OAc)2-catalyzed tandem oxidation of C[sbnd]N, C[sbnd]C, and C(sp3)–H bonds: Concise synthesis of 1-aroylisoquinoline, oxoaporphine, and 8-oxyprotoberberine alkaloids
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A catalytic tandem oxidation of C[sbnd]N, C[sbnd]C, and C(sp3)–H bonds is developed. This tandem oxidation is applied to two-step total syntheses of papaveraldine and pulcheotine A. Additionally, the total synthesis of liriodenine is achieved in six steps from homopiperonyl alcohol and 2-bromophenylacetonitrile by applying this catalytic tandem oxidation. Moreover, the direct conversion of xylopinine to 8-oxypseudopalmatine in a 76% yield demonstrates the versatility of this catalytic reaction.
- Nishimoto, Saeko,Nakahashi, Hiromichi,Toyota, Masahiro
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- Acceptorless dehydrogenation of amines and alcohols using simple ruthenium chloride
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A highly efficient, economic and environmental friendly catalyst system has been developed for the dehydrogenation of alcohols and amines using simple RuCl3·nH2O and N-benzylhexamethylenetetramine. The in situ catalyst system efficiently oxidized the primary and secondary amines and secondary alcohols into nitrile, imine and ketone products, respectively in moderate to excellent yields. The developed catalyst system was also found to be efficient for the dehydrogenation of N-heterocyles. A detailed mechanism study revealed the first example of N-benzylhexamethylenetetramine (HMTA-Bz) being simultaneously acting as base, reducing agent and hydride source to generate the [Ru(II)(H)2] species as the active catalyst. The mechanism studies also revealed both the alcohol and amine oxidation involves dehydrogenative pathway with the evolution of hydrogen as the only by-product. The developed catalyst system also provides possible platform for the release of hydrogen from liquid organic hydrogen carriers (LOHCs).
- Barteja, Parul,Devi, Preeti,Kannan, Muthukumar,Muthaiah, Senthilkumar
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- Iodine-catalyzed convergent aerobic dehydro-aromatization toward benzazoles and benzazines
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An iodine-catalyzed aerobic dehydro-aromatization has been developed, providing straightforward and efficient access to various benzoazoles and benzoazines. The present transition-metal-free protocol enables the dehydro-aromatization of tetrahydrobenzazoles and tetrahydroquinolines with molecular oxygen as the green oxidant, along with some other N-heterocycles. Hence, a broad range of heteroaromatic compounds are generated in moderate to good yields under facile reaction conditions.
- Chen, Shanping,Deng, Guo-Jun,Jiang, Pingyu,Ni, Penghui,Tuo, Xiaolong,Wang, Xiaodong
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p. 8348 - 8351
(2020/03/11)
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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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- Ir-Catalyzed Reversible Acceptorless Dehydrogenation/Hydrogenation of N-Substituted and Unsubstituted Heterocycles Enabled by a Polymer-Cross-Linking Bisphosphine
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The polystyrene-cross-linking bisphosphine ligand PS-DPPBz was effective for the Ir-catalyzed reversible acceptorless dehydrogenation/hydrogenation of N-heterocycles. Notably, this protocol is applicable to the dehydrogenation of N-substituted indoline derivatives with various N-substituents with different electronic and steric natures. A reaction pathway involving oxidative addition of an N-adjacent C(sp3)-H bond to a bisphosphine-coordinated Ir(I) center is proposed for the dehydrogenation of N-substituted substrates.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5240 - 5245
(2020/07/03)
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