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Pd/C-Catalyzed transfer hydrogenation ofN-H indoles with trifluoroethanol and tetrahydroxydiboron as the hydrogen source
Under the guidance of the known mechanism of the hydrogenation of indoles and transfer hydrogenation with tetrahydroxydiboron (B2(OH)4), Pd/C catalyzed transfer hydrogenation ofN-H indoles with trifluoroethanol and tetrahydroxydiborane as the hydrogen source has been developed. This provides an efficient strategy and catalytic system for the reduction of un-activatedN-H indoles, andN-H indolines are obtained with good to excellent yields. In addition, a series of the isotopic labelling experiments were carried out to probe the mechanism.
Zhou, Xiao-Yu,Chen, Xia
supporting information
p. 548 - 551
(2021/02/06)

Concerning the preparation of 6-bromotryptamine
Most of the previous syntheses of the marine natural product 6-bromotryptamine have almost certainly led to partial debromination resulting in an impure product containing tryptamine. We show that loss of bromine occurs when lithium aluminum hydride is employed as a reducing agent in the final reaction step leading to 6-bromotryptamine. Reductive-debromination is also likely to intrude during some of the syntheses of 6-bromoindole, the typical precursor to 6-bromotryptamine. None of the seven described syntheses of 6-bromotryptamine that involve a reduction sequence from 6-bromoindole have reported elemental analyses as a measure of purity.
Scott Wiens,Johnson, Jerry L.,Gribble, Gordon W.
(2021/03/15)

Organometallic Synthesis of Bimetallic Cobalt-Rhodium Nanoparticles in Supported Ionic Liquid Phases (CoxRh100?x@SILP) as Catalysts for the Selective Hydrogenation of Multifunctional Aromatic Substrates
The synthesis, characterization, and catalytic properties of bimetallic cobalt-rhodium nanoparticles of defined Co:Rh ratios immobilized in an imidazolium-based supported ionic liquid phase (CoxRh100?x@SILP) are described. Following an organometallic approach, precise control of the Co:Rh ratios is accomplished. Electron microscopy and X-ray absorption spectroscopy confirm the formation of small, well-dispersed, and homogeneously alloyed zero-valent bimetallic nanoparticles in all investigated materials. Benzylideneacetone and various bicyclic heteroaromatics are used as chemical probes to investigate the hydrogenation performances of the CoxRh100?x@SILP materials. The Co:Rh ratio of the nanoparticles is found to have a critical influence on observed activity and selectivity, with clear synergistic effects arising from the combination of the noble metal and its 3d congener. In particular, the ability of CoxRh100?x@SILP catalysts to hydrogenate 6-membered aromatic rings is found to experience a remarkable sharp switch in a narrow composition range between Co25Rh75 (full ring hydrogenation) and Co30Rh70 (no ring hydrogenation).
Rengshausen, Simon,Van Stappen, Casey,Levin, Natalia,Tricard, Simon,Luska, Kylie L.,DeBeer, Serena,Chaudret, Bruno,Bordet, Alexis,Leitner, Walter
(2020/12/22)

Heterogeneous Hydrogenation of Quinoline Derivatives Effected by a Granular Cobalt Catalyst
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
(2021/11/22)

Palladium-Catalyzed Direct and Specific C-7 Acylation of Indolines with 1,2-Diketones
The indole scaffold is a ubiquitous and useful substructure, and extensive investigations have been conducted to construct the indole framework and/or realize indole modification. Nevertheless, the direct selective functionalization on the benzenoid core must overcome the high activity of the C-3 position and still remains highly challenging. Herein, a palladium-catalyzed direct and specific C-7 acylation of indolines in the presence of an easily removed directing group was developed. This strategy usually is considered as a practical strategy for the preparation of acylated indoles because indoline can be easily converted to indole under oxidation conditions. In particular, our strategy greatly improved the alkacylation yield of indolines for which only an unsatisfactory yield could be achieved in the previous studies. Furthermore, the reaction can be scaled up to gram level in the standard reaction conditions with a much lower palladium loading (1 mol %).
Xie, Guilin,Zhao, Yuhan,Cai, Changqun,Deng, Guo-Jun,Gong, Hang
supporting information
p. 410 - 415
(2021/01/26)

Stereospecific N-acylation of indoles and corresponding microwave mediated synthesis of pyrazinoindoles using hexafluoroisopropanol
We envisioned a facile construction of diversified pyrazinoindoles by using 1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) as the solvent and catalyst, hence eliminating metal catalyzed routes for its development. The process is facilitated by HFIP that has emerged as a powerful tool for development of novel fused heterocycles. This cascade approach blends the asymmetric N-acylation with consecutive intramolecular cyclisation via Pictet-Spengler reaction as an efficient tool forming overall two stereogenic centers. Our approach deals with incorporation of L-amino acid on substituted indoles to provide the chiral N-acylated indole precursor followed by cyclisation to access pyrazinoindole derivatives in high enantiomeric excess up to >99% in good to excellent yields, which have great potential as molecular scaffolds in drug discovery. We have also described the mechanistic course of the reaction based on density functional theory.
Singh, Aarushi,Singh, Snigdha,Sewariya, Shubham,Singh, Nidhi,Singh, Prashant,Kumar, Ajay,Bandichhor, Rakeshwar,Chandra, Ramesh
(2021/02/27)

Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
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
supporting information
p. 7738 - 7744
(2021/05/07)

Green oxidation of amines by a novel cold-adapted monoamine oxidase mao p3 from psychrophilic fungi pseudogymnoascus sp. p3
The use of monoamine oxidases (MAOs) in amine oxidation is a great example of how biocatalysis can be applied in the agricultural or pharmaceutical industry and manufacturing of fine chemicals to make a shift from traditional chemical synthesis towards more sustainable green chemistry. This article reports the screening of fourteen Antarctic fungi strains for MAO activity and the discovery of a novel psychrozyme MAOP3 isolated from the Pseudogymnoascus sp. P3. The activity of the native enzyme was 1350 ± 10.5 U/L towards a primary (n-butylamine) amine, and 1470 ± 10.6 U/L towards a secondary (6,6-dimethyl-3-azabicyclohexane) amine. MAO P3 has the potential for applications in biotransformations due to its wide substrate specificity (aliphatic and cyclic amines, pyrrolidine derivatives). The psychrozyme operates at an optimal temperature of 30? C, retains 75% of activity at 20? C, and is rather thermolabile, which is beneficial for a reduction in the overall costs of a bioprocess and offers a convenient way of heat inactivation. The reported biocatalyst is the first psychrophilic MAO; its unique biochemical properties, substrate specificity, and effectiveness predispose MAO P3 for use in environmentally friendly, low-emission biotransformations.
Bia?kowska, Aneta M.,Jod?owska, Iga,Szymczak, Kamil,Twarda-Clapa, Aleksandra
supporting information

(2021/10/25)

Palladium supported on magnesium hydroxyl fluoride: An effective acid catalyst for the hydrogenation of imines and N-heterocycles
Palladium catalysts supported on acidic fluorinated magnesium hydroxide Pd/MgF2-x(OH)x were prepared through precipitation or impregnation methods. Applications to the hydrogenation of various aldimines and ketimines resulted in good catalytic activities at mild temperatures using one atmosphere of hydrogen. Quinolines, pyridines and other N-heterocycles were successfully hydrogenated at higher temperature and hydrogen pressure using low palladium loadings and without the use of any acid additive. Such reactivity trend confirmed the positive effect of the Br?nsted and Lewis acid sites from the fluorinated magnesium hydroxide support resulting in the effective pre-activation of N-heterocycle substrates and therefore in the good catalytic activity of the palladium nanoparticles during the hydrogenations. As demonstrated in the hydrogenation of imines, the catalyst was recycled up to 10 times without either loss of activity or palladium leaching. This journal is
Agbossou-Niedercorn, Francine,Corre, Yann,Dongare, Mohan K.,Kemnitz, Erhard,Kokane, Reshma,Michon, Christophe,Umbarkar, Shubhangi B.
supporting information
p. 19572 - 19583
(2021/11/04)

Utilization of renewable formic acid from lignocellulosic biomass for the selective hydrogenation and/or N-methylation
Lignocellulosic biomass is one of the most abundant renewable sources in nature. Herein, we have developed the utilization of renewable formic acid from lignocellulosic biomass as a hydrogen source and a carbon source for the selective hydrogenation and further N-methylation of various quinolines and the derivatives, various indoles under mild conditions in high efficiencies. N-methylation of various anilines is also developed. Mechanistic studies indicate that the hydrogenation occurs via a transfer hydrogenation pathway.
Zhou, Chao-Zheng,Zhao, Yu-Rou,Tan, Fang-Fang,Guo, Yan-Jun,Li, Yang
p. 4724 - 4728
(2021/09/06)

Aromatic compound hydrogenation and hydrodeoxygenation method and application thereof
The invention belongs to the technical field of medicines, and discloses an aromatic compound hydrogenation and hydrodeoxygenation method under mild conditions and application of the method in hydrogenation and hydrodeoxygenation reactions of the aromatic compounds and related mixtures. Specifically, the method comprises the following steps: contacting the aromatic compound or a mixture containing the aromatic compound with a catalyst and hydrogen with proper pressure in a solvent under a proper temperature condition, and reacting the hydrogen, the solvent and the aromatic compound under the action of the catalyst to obtain a corresponding hydrogenation product or/and a hydrodeoxygenation product without an oxygen-containing substituent group. The invention also discloses specific implementation conditions of the method and an aromatic compound structure type applicable to the method. The hydrogenation and hydrodeoxygenation reaction method used in the invention has the advantages of mild reaction conditions, high hydrodeoxygenation efficiency, wide substrate applicability, convenient post-treatment, and good laboratory and industrial application prospects.
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Paragraph 0094-0095; 0114-0122

(2021/05/29)

CO2-tuned highly selective reduction of formamides to the corresponding methylamines
We herein describe an efficient, CO2-tuned and highly selective C-O bond cleavage of N-methylated formanilides. With easy-to-handle and commercially available NaBH4 as the reductant, a variety of formanilides could be turned into the desired tertiary amines in moderate to excellent yields. The role of CO2 has been investigated in detail, and the mechanism is proposed on the basis of experiments.
Chao, Jianbin,Guo, Zhiqiang,Pang, Tengfei,Wei, Xuehong,Xi, Chanjuan,Yan, Leilei
supporting information
p. 7534 - 7538
(2021/10/12)

Zirconium-hydride-catalyzed site-selective hydroboration of amides for the synthesis of amines: Mechanism, scope, and application
Developing mild and efficient catalytic methods for the selective synthesis of amines is a longstanding research objective. In this respect, catalytic deoxygenative amide reduction has proven to be promising but challenging, as this approach necessitates selective C–O bond cleavage. Herein, we report the selective hydroboration of primary, secondary, and tertiary amides at room temperature catalyzed by an earth-abundant-metal catalyst, Zr-H, for accessing diverse amines. Various readily reducible functional groups, such as esters, alkynes, and alkenes, were well tolerated. Furthermore, the methodology was extended to the synthesis of bio- and drug-derived amines. Detailed mechanistic studies revealed a reaction pathway entailing aldehyde and amido complex formation via an unusual C–N bond cleavage-reformation process, followed by C–O bond cleavage.
Han, Bo,Jiao, Haijun,Wu, Lipeng,Zhang, Jiong
p. 2059 - 2067
(2021/09/02)

Discovery of tetrahydroquinolines and benzomorpholines as novel potent RORγt agonists
The retinoic acid receptor-related orphan receptor γt (RORγt) is an important nuclear receptor that regulates the differentiation of Th17 cells and production of interleukin 17(IL-17). RORγt agonists increase basal activity of RORγt and could provide a potential approach to cancer immunotherapy. Herein, hit compound 1 was identified as a weak RORγt agonist during in-house library screening. Changes in LHS core of 1 led to the identification of tetrahydroquinoline compound 6 as a partial RORγt agonist (max. act. = 39.3%). Detailed structure-activity relationship on substituent of the LHS core, amide linker and RHS arylsulfonyl moiety was explored and a novel series of tetrahydroquinolines and benzomorpholines was discovered as potent RORγt agonists. Tetrahydroquinoline compound 8g (EC50 = 8.9 ± 0.4 nM, max. act. = 104.5%) and benzomorpholine compound 9g (EC50 = 7.5 ± 0.6 nM, max. act. = 105.8%) were representative compounds with high RORγt agonistic activity in dual FRET assay, and they showed good activity in cell-based Gal4 reporter gene assay and Th17 cell differentiation assay (104.5% activation at 300 nM of 8g; 59.4% activation at 300 nM of 9g). The binding modes of 8g and 9g as well as the two RORγt inverse agonists accidentally discovered were also discussed.
Xia, Yuehan,Yu, Mingcheng,Zhao, Yunpeng,Xia, Li,Huang, Yafei,Sun, Nannan,Song, Meiqi,Guo, Huimin,Zhang, Yunyi,Zhu, Di,Xie, Qiong,Wang, Yonghui
(2020/12/04)

Near-infrared mitochondrial fluorescence probe and synthesis method thereof
The invention provides a near-infrared mitochondrial fluorescence probe and a synthesis method thereof. The structure of the fluorescent probe is malachite green modified by a nitrogen terminal of a rigid five-membered ring. The structure of the fluorescent probe is shown as (1), the emission wavelength of the fluorescent probe is 685 nm and reaches a near-infrared region, and the fluorescent probe is inhibited from rotating after entering mitochondria due to rapid quenching of rotating fluorescence in a solution, so that near-infrared light fluorescence is emitted, the signal-to-noise ratio is greatly improved, and the fluorescent probe has a wide application prospect in mitochondria wash-free marking.
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Paragraph 0031-0036; 0052-0056; 0065-0069

(2020/07/13)

Aerobic Dehydrogenation of N-Heterocycles with Grubbs Catalyst: Its Application to Assisted-Tandem Catalysis to Construct N-Containing Fused Heteroarenes
An aerobic dehydrogenation of nitrogen-containing heterocycles catalyzed by Grubbs catalyst is developed. The reaction is applicable to various nitrogen-containing heterocycles. The exceptionally high functional group compatibility of this method was confirmed by the oxidation of an unprotected dihydroindolactam V to indolactam V. Furthermore, by taking advantage of the oxygen-mediated structural change of the Grubbs catalyst, we integrated ring-closing metathesis and subsequent aerobic dehydrogenation to develop the novel assisted-tandem catalysis using molecular oxygen as a chemical trigger. The utility of the assisted-tandem catalysis was demonstrated by the concise synthesis of N-containing fused heteroarenes including a natural antibiotic, pyocyanine.
Kawauchi, Daichi,Noda, Kenta,Komatsu, Yoshiyuki,Yoshida, Kei,Ueda, Hirofumi,Tokuyama, Hidetoshi
supporting information
p. 15793 - 15798
(2020/10/12)

Hydrogenation or Dehydrogenation of N-Containing Heterocycles Catalyzed by a Single Manganese Complex
A highly chemoselective base-metal catalyzed hydrogenation and acceptorless dehydrogenation of N-heterocycles is presented. A well-defined Mn complex operates at low catalyst loading (as low as 2 mol %) and under mild reaction conditions. The described catalytic system tolerates various functional groups, and the corresponding reduced heterocycles can be obtained in high yields. Experimental studies indicate a metal-ligand cooperative catalysis mechanism.
Borghs, Jannik C.,Rueping, Magnus,Zubar, Viktoriia
supporting information

(2020/05/19)

Ir-Catalyzed Reversible Acceptorless Dehydrogenation/Hydrogenation of N-Substituted and Unsubstituted Heterocycles Enabled by a Polymer-Cross-Linking Bisphosphine
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
supporting information
p. 5240 - 5245
(2020/07/03)

Convenient synthesis of cobalt nanoparticles for the hydrogenation of quinolines in water
Easily accessible cobalt nanoparticles are prepared by hydrolysis of NaBH4 in the presence of inexpensive Co(ii) salts. The resulting material is an efficient catalyst for the hydrogenation of quinoline derivatives in water. The activity and chemoselectivity of this catalyst are comparable to other cobalt-based heterogeneous catalysts.
Beller, Matthias,Dorcet, Vincent,Fischmeister, Cedric,Hervochon, Julien,Junge, Kathrin
p. 4820 - 4826
(2020/08/14)

NHC-Palladium(II) Mononuclear and Binuclear Complexes Containing Phenylene-Bridged Bis(thione) Ligands: Synthesis, Characterization, and Catalytic Activities
A series of mono- and binuclear Pd(II) complexes with N-heterocyclic carbene (NHC) and phenylene-bridged bis(thione) (SCS) ligands were prepared and characterized by 1H and 13C NMR spectroscopy, IR, and mass spectrometry. The molecular structures of 1b, 2a, and 3b have been determined by the single-crystal X-ray diffraction method. The catalytic activities of the synthesized palladium complexes in the regioselective reduction of quinolines to the corresponding 1,2,3,4-tetrahydroquinolines were thoroughly investigated with ammonia-borane under mild reaction conditions. It is observed that the activities of the binuclear Pd(NHC) complexes were higher than those of the corresponding mononuclear complexes under the same conditions.
Jia, Wei-Guo,Gao, Li-Li,Wang, Zhi-Bao,Wang, Jing-Jing,Sheng, En-Hong,Han, Ying-Feng
p. 1790 - 1798
(2020/05/14)

Catalytic reduction of aromatic ring in aqueous medium
A method of reducing an aromatic ring under relatively mild condition using sub-nano particles of a transition metal supported on super paramagnetic iron oxide nanoparticles (SPIONs). The catalyst is efficient for catalyzing the reduction of both carbocyclic and heterocyclic compound. In compound comprising both carbocyclic and heterocyclic aromatic rings, the catalyst displays high regioselectivity for the heterocyclic ring.
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Page/Page column 10; 16-17

(2020/05/04)

Transition-Metal-Free Stereospecific Oxidative Annulative Coupling of Indolines with Aziridines
Tandem C-N bond formation for the oxidative annulation of indolines with aziridines is accomplished employing the combination of DDQ and NaOCl at ambient conditions. Optically active aziridine can be coupled with high enantiomeric purity (>99% ee). The substrate scope, stereocontrol with the enantioenriched substrate, and scale-up are the important practical advantages.
Karjee, Pallab,Sarkar, Tanumay,Kar, Subhradeep,Punniyamurthy, Tharmalingam
p. 8261 - 8270
(2020/07/25)

Efficient synthesis process of medical intermediate 5-bromoindole
The invention discloses an efficient synthesis process of a medical intermediate 5-bromoindole, comprising the following steps of: using an indole compound as a raw material, carrying out low-pressureliquid-phase hydrogenation to destroy five-membered ring conjugation of indole to obtain an indoline compound; enabling the indoline compound to react with an acylation reagent, and protecting nitrogen, so as to obtain an N-acyl indoline compound; carrying out bromination on the N-acyl indoline compound to obtain a 5-bromo-N-acyl indoline compound; carrying out deacylation protection on the 5-bromo-N-acyl indoline compound to obtain a 5-bromoindoline compound; and carrying out oxidative dehydrogenation on the 5-bromoindoline compound by using oxygen or air under the action of a cuprous catalyst and nitric oxide to obtain the target compound 5-bromoindole. The steps involved in the process are convenient to operate, the conditions are mild, and environmental pollution is reduced; finally,the prepared product is high in yield, high in purity and low in energy consumption.
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Paragraph 0036-0038; 0043-0045; 0050-0052

(2020/08/06)

Phyllosilicate-derived Nickel-cobalt Bimetallic Nanoparticles for the Catalytic Hydrogenation of Imines, Oximes and N-heteroarenes
The development of cost-effective, noble metal-free catalytic systems for the hydrogenation of unsaturated aliphatic, aromatic, and heterocyclic compounds is fundamental for future valorization of general feedstock. With this aim, we report here the preparation of highly dispersed bimetallic Ni/Co nanoparticles (NPs), by a one-pot deposition-precipitation of Ni and Co phases onto mesoporous SBA-15 silica. By adjusting the chemical composition in the starting mixture, three supported catalysts with different Ni to Co weight ratios were obtained, which were further subjected to treatments under reducing conditions at high temperatures. Characterization of the resulting solids evidenced a homogenous distribution of Ni and Co elements forming the NPs, the best results being obtained for Ni/Co-2 : 2 samples, for which 50 wt.percent Ni–50 wt.percent Co NPs are found located on the surface of the residual phyllosilicate. Ni/Co-2 : 2, presenting the best performances for the hydrogenation of 2-methyl-quinoline, was further evaluated in the catalytic hydrogenation of selected imines, oximes and N-heteroarenes. Due to the high dispersion of bimetallic Ni?Co NPs, excellent properties (activity and selectivity) in the conversion of the selected substrates are reported.
Ciotonea, Carmen,Hammi, Nisrine,Dhainaut, Jérémy,Marinova, Maya,Ungureanu, Adrian,El Kadib, Abdelkrim,Michon, Christophe,Royer, Sébastien
p. 4652 - 4663
(2020/08/19)

Dual-Active-Sites Design of Co@C Catalysts for Ultrahigh Selective Hydrogenation of N-Heteroarenes
The dual-active-sites Co@C catalyst provides a general powerful strategy to break the limitation of scaling relation on traditional metal surfaces and thus affords unprecedentedly selective hydrogenation of various N-heteroarenes as well as high activity and stability. A porous carbon shell not only allows H2 diffusion to Co sites for activation but also blocks accessibility of N-heteroarenes, and the hydrogenation of N-heteroarenes is achieved on carbon by the spilled hydrogen from Co sites. In addition, the presence of surface/subsurface carbon at the Co sites shows high anti-sulfur poisoning and anti-oxidant capability. Ideal heterogeneous metal hydrogenation catalysts are featured by simultaneously high activity, selectivity, and stability. Herein, we report a general yet powerful strategy to design and fabricate dual-active-sites Co@C core-shell nanoparticle for boosting selective hydrogenation of various N-heteroarenes. It can break the limitation of scaling relation on traditional metal surfaces, and thus afford unprecedentedly high selectivity, activity, and stability. Combining kinetics analysis and DFT calculations with multiple techniques directly unveil that the critical porous carbon shell with a pore size of 0.53 nm not only allows H2 diffusion to Co sites for activation and blocks accessibility of N-heteroarenes but also catalyzes hydrogenation of N-heteroarenes via hydrogen spillover from Co sites. In addition, the presence of surface/subsurface carbon at the Co sites shows high anti-sulfur poisoning and anti-oxidant capability. This work is valuable for guiding the design and manipulation of cost-effective and robust hydrogenation catalysts. Our research can provide an environmentally friendly approach to afford unprecedentedly selective N-heteroarenes hydrogenation, which will greatly reduce the resource and energy consumption and decrease the amount of waste discharge and water pollution. Therefore, these results could help in achieving the “Clean water and sanitation” goal in the 10 UN Sustainable Development Goals. Meanwhile, the products of N-heteroarenes hydrogenation are the core structural motifs in both fine and bulk chemicals, which will make our life more beautiful. Thus, our research also benefits the “Good health and well-being” goal.
Zhang, Sai,Gan, Jie,Xia, Zhaoming,Chen, Xiao,Zou, Yong,Duan, Xuezhi,Qu, Yongquan
supporting information
p. 2994 - 3006
(2020/09/04)

Reversible aerobic oxidative dehydrogenation/hydrogenation of N-heterocycles over AlN supported redox cobalt catalysts
N-heterocycles with quinoline and tetrahydroquinoline structures are highly important in pharmaceutical and chemical industries, and their highly efficient mutual transformations are vital but still challenging. In the present work, AlN supported redox cobalt catalysts (Co3O4/AlN and Co/AlN) were prepared, which could achieve the reversible aerobic oxidative dehydrogenation/hydrogenation of N-heterocycles with good performances. The catalytic performances were stem from the strong interaction between Co species with AlN support, which were confirmed by the characterizations of Raman, XPS, UV–vis DRS, and H2-TPR etc. Both of the catalysts showed good stabilities and reusabilities for the titled reactions. Besides, the gram-scale experiments achieved with good yields to corresponding products, revealing the present protocol possesses great potential applications in industry. The strategy of using redox Co-based catalyst not only provides a potential catalyst for the reversible hydrogenation/oxidative dehydrogenation reactions but also replenishes methods for constructing of other redox catalyst, especially with AlN as a carrier.
He, Zhen-Hong,Sun, Yong-Chang,Wang, Kuan,Wang, Zhong-Yu,Guo, Pan-Pan,Jiang, Chong-Shan,Yao, Man-Qing,Li, Zhu-Hui,Liu, Zhao-Tie
(2020/09/16)

A General Catalyst Based on Cobalt Core–Shell Nanoparticles for the Hydrogenation of N-Heteroarenes Including Pyridines
Herein, we report the synthesis of specific silica-supported Co/Co3O4 core–shell based nanoparticles prepared by template synthesis of cobalt-pyromellitic acid on silica and subsequent pyrolysis. The optimal catalyst material allows for general and selective hydrogenation of pyridines, quinolines, and other heteroarenes including acridine, phenanthroline, naphthyridine, quinoxaline, imidazo[1,2-a]pyridine, and indole under comparably mild reaction conditions. In addition, recycling of these Co nanoparticles and their ability for dehydrogenation catalysis are showcased.
Beller, Matthias,Chandrashekhar, Vishwas G.,Jagadeesh, Rajenahally V.,Kreyenschulte, Carsten,Murugesan, Kathiravan
supporting information
p. 17408 - 17412
(2020/08/21)

Regioselective Formation of Substituted Indoles: Formal Synthesis of Lysergic Acid
A Diels–Alder reaction-based strategy for the synthesis of indoles and related heterocycles is reported. An intramolecular cycloaddition of alkyne-tethered 3-aminopyrones gives 4-substituted indolines in good yield and with complete regioselectivity. Additional substitution is readily tolerated in the transformation, allowing synthesis of complex and non-canonical substitution patterns. Oxidative conditions give the corresponding indoles. The strategy also allows the synthesis of carbazoles. The method was showcased in a formal synthesis of lysergic acid.
Beaudry, Christopher M.,Points, Gary L.,Stout, Kenneth T.
supporting information
p. 16655 - 16658
(2020/12/01)

Base-assisted intramolecular c-n coupling reaction from nh2-bound cyclopalladated l -phenylalanine to indoline-2-carboxylic acid
The deprotonative intramolecular-amination reaction of phenylalanine-derived palladacycles has been investigated to highlight a facile carbonate-assisted N-H activation before the C-N bond formation. A major counterion effect led to divergent pathways whereby the SPhos-Pd complexes with iodine, triflate, or trifluoroacetate anions were key intermediates to afford access to (S)-2-indolinecarboxylic acid derivatives.
Afonso, Carlos,Brière, Jean-Fran?ois,Coufourier, Sébastien,Gandon, Vincent,Hoarau, Christophe,Jacquin-Labarre, Aurélien,Journot, Guillaume,Le Foll, Alexandra,Levacher, Vincent,Tamion, Rodolphe
p. 767 - 773
(2020/03/25)

Short time synthesis of titania modified-CMK-3 carbon mesostructure as support for Ir-catalyst applied in catalytic hydrotreating
Ti-CMK-3 carbon mesoporous was prepared using a novel synthesis method. This new method avoids the hard template synthesis used commonly. The method developed here, allows to reduce time, energy consumptionand cost. Structural and textural characterization of the titanium modified-mesoporous carbonwas performed by N2 adsorption, XRD, UV–vis-DRS, Raman spectroscopy and TEM. The characterization results indicated that the textural and structural properties of the material synthesized by the short time method are comparable with the properties of the material prepared by the hard template method. Ti modified-mesoporous carbon was used as support of the iridium nanoparticles, in order to prepare a catalyst to be tested in model hydrotreating reactions. The catalyst obtained by wet impregnation with iridium acetylacetonate were characterized by ICP-AES, H2 chemisorption, TEM, XPS and FTIR of adsorbed pyridine. The high Ir dispersion and small particle size, along with the moderate Lewis acidity generated by the presence of titanium in the support, were responsible for the good performance and stability of the catalyst in the hydrogenation of tetralin in presence of nitrogen compounds. Main advantage of the present study is the reduction of time and cost in the synthesis of the new material and the applicability for HDT reactions.
Beltramone, Andrea R.,Juárez, Juliana M.,Ledesma, Brenda C.
p. 210 - 216
(2018/04/17)

Homogeneous cobalt-catalyzed deoxygenative hydrogenation of amides to amines
The first general and efficient cobalt-catalyzed deoxygenative hydrogenation of amides to amines is presented. The optimal catalytic system based on a combination of [Co(NTf2)2] and (p-anisyl)triphos (L3) in the presence of [Me3SiOTf] as acidic co-catalyst facilitates the direct hydrogenation of a broad range of amides to the corresponding amines under mild conditions. A set of control experiments indicate that, after the initial reduction of the amide carboxylic group to the well-known hemiaminal intermediate, the reaction mainly proceeds through C-O bond cleavage though other pathways might be also involved to a minor extent. This journal is
Papa, Veronica,Cabrero-Antonino, Jose R.,Spannenberg, Anke,Junge, Kathrin,Beller, Matthias
p. 6116 - 6128
(2020/11/03)

Sodium Triethylborohydride-Catalyzed Controlled Reduction of Unactivated Amides to Secondary or Tertiary Amines
The first transition-metal-free catalytic protocol for controlled reduction of amide functions using cheap and bench-stable hydrosilanes as reducing agents has been established. By altering the hydrosilane and solvent, the new method enables the selective cleavage of unactivated C-O bonds in amides and allows the C-N bonds to selectively break via the deacylated cleavage. Overall, this novel process may offer a versatile alternative to current methodologies employing stoichiometric metal systems for the controlled reduction of carboxamides.
Yao, Wubing,He, Lili,Han, Deman,Zhong, Aiguo
(2019/11/14)

Sodium Triethylborohydride-Catalyzed Controlled Reduction of Unactivated Amides to Secondary or Tertiary Amines
The first transition-metal-free catalytic protocol for controlled reduction of amide functions using cheap and bench-stable hydrosilanes as reducing agents has been established. By altering the hydrosilane and solvent, the new method enables the selective cleavage of unactivated C-O bonds in amides and allows the C-N bonds to selectively break via the deacylated cleavage. Overall, this novel process may offer a versatile alternative to current methodologies employing stoichiometric metal systems for the controlled reduction of carboxamides.
Yao, Wubing,He, Lili,Han, Deman,Zhong, Aiguo
p. 14627 - 14635
(2019/12/02)

Ru subnanoparticles on N-doped carbon layer coated SBA-15 as efficient Catalysts for arene hydrogenation
The N-doped carbon layer coated SBA-15 support has been accomplished via a pyrolysis process. The ultra-low loading Ru nanoparticles (ca. 0.1 wt.%) was incorporated into the support by impregnation and the sequential reduction. The images of HAADF-STEM revealed that the Ru particles with sub-1-nm size (0.2-0.7 nm) were uniformly dispersed on the support. The ultrafine Ru particles displayed the excellent activity for the hydrogenation of olefins, arenes, phenol derivatives and heteroarenes in aqueous phase. The aliphatic or alicyclic compounds were produced selectively without the hydrogenolysis of C–O and C–N bonds. The high turnover frequency (TOF) values can reach up to 10,000 h?1. Notably, the activity of these catalysts improved dramatically with decreasing the sizes of Ru particles. Meanwhile, the N-doped carbon layer coating endowed the high stability of the Ru catalysts and prevented the leaching of the Ru species owning to the strong interaction between doped-N atoms and the ultrafine Ru particles. Overall, this work provides a highly attractive strategy to construct the supported sub-1-nm Ru particles utilized for the aqueous hydrogenation.
Qian, Wei,Lin, Lina,Qiao, Yunxiang,Zhao,Xu, Zichen,Gong, Honghui,Li,Chen,Huang, Rong,Hou, Zhenshan
(2019/08/12)

Iridium-Catalyzed Hydrogenation and Dehydrogenation of N-Heterocycles in Water under Mild Conditions
An efficient catalytic method is presented for the hydrogenation of N-heterocycles. The iridium-based catalyst operates under mild conditions in water without any co-catalyst or stoichiometric additives. The catalyst also promotes the reverse reaction of dehydrogenation of N-heterocycles, hence displaying appropriate characteristics for a future hydrogen economy based on liquid organic hydrogen carriers (LOHCs).
Wang, Shengdong,Huang, Haiyun,Bruneau, Christian,Fischmeister, Cédric
p. 2350 - 2354
(2019/05/21)

A Reusable Cobalt Catalyst for Reversible Acceptorless Dehydrogenation and Hydrogenation of N-Heterocycles
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
p. 2449 - 2457
(2019/05/10)

Dearomatization-Rearomatization Strategy for Reductive Cross-Coupling of Indoles with Ketones in Water
N-Alkylation of indoles is one of the important pathways for the construction of various biologically active indole molecules. Using ketones as N-alkylation reagent for indoles has been a great challenge not only because of the competing alkylation reaction of C-3 position but also because of the poor nucleophilicity of the nitrogen atom of indole, in addition to the steric hindrance and lower electrophilicity of the ketones. A dearomatization-rearomatization strategy has been developed for reductive cross-coupling of indoles with ketones in water. Various functional groups and other heterocyclic compounds are tolerated.
Wang, Zemin,Zeng, Huiying,Li, Chao-Jun
p. 2302 - 2306
(2019/04/10)

Re-Catalyzed Annulations of Weakly Coordinating N-Carbamoyl Indoles/Indolines with Alkynes via C?H/C?N Bond Cleavage
Described herein are rhenium-catalyzed [3+2] annulations of N-carbamoyl indoles with alkynes via C?H/C?N bond cleavage, which provide rapid access to fused-ring pyrroloindolone derivatives. For the first time, the weakly coordinating O-directing group was successfully employed in rhenium-catalyzed C?H activation reactions, enabled by the unique catalytic trio of Re2(CO)10, Me2Zn and ZnCl2. Mechanistic studies revealed that aminozinc species plays an important role in the reaction. Based on the mechanistic understanding, a more powerful catalytic trio of Re2(CO)10, [MeZnNPh2]2 and Zn(OTf)2 was devised and applied successfully in the [4+2] annulations of indolines and alkynes affording pyrroloquinolinone derivatives.
Yang, Yunhui,Wang, Congyang
supporting information
p. 8245 - 8248
(2019/05/28)

Design, synthesis and biological evaluation of novel 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole triazole derivatives as potent TRPV1 antagonists
Reported herein is the design, synthesis, and pharmacologic evaluation of a class of TRPV1 antagonists constructed on 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole as A-region and triazole as B-region. The SAR analysis indicated that 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole analogues displayed excellent antagonism of hTRPV1 activation by capsaicin and showed better potency compared to the corresponding dihydroindole analogues. Optimization of this design led to the eventual identification of 2-((1-(2-(trifluoromethyl)phenyl)-1H-1,2,3-triazol-4-yl)methyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (6g), a potent TRPV1 antagonist. In vitro, using cells expressing recombinant human TRPV1 channels, 6g displayed potent antagonism activated by capsaicin (IC50 = 0.075 μM) and only partially blocked acid activation of TRPV1. In vivo, 6g exhibited good efficacy in capsaicin-induced and heat-induced pain models and had almost no hyperthermia side-effect. Furthermore, pharmacokinetic studies revealed that compound 6g had a superior oral exposure after oral administration in rats. To understand its binding interactions with the receptor, the docking study of 6g was performed in rTRPV1 model and showed an excellent fit to the binding site. On the basis of its superior profiles, 6g could be considered as the lead candidate for the further development of antinociceptive drugs.
Li, Jinyu,Nie, Cunbin,Qiao, Yue,Hu, Jing,Li, Qifei,Wang, Qiang,Pu, Xiaohui,Yan, Lin,Qian, Hai
p. 433 - 445
(2019/06/18)

Hydrophobic Metal Halide Perovskites for Visible-Light Photoredox C?C Bond Cleavage and Dehydrogenation Catalysis
Two-dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1-hexadecylammonium (HDA) between the inorganic layers. We observed visible-light absorption, narrow-band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Owing to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline-2-carboxylic acids. (HDA)2PbI4 or (HDA)2SnI4 were investigated as photoredox catalysts for these reactions, and quantitative conversion and high yields were observed with the former.
Hong, Zonghan,Chong, Wee Kiang,Ng, Andrew Yun Ru,Li, Mingjie,Ganguly, Rakesh,Sum, Tze Chien,Soo, Han Sen
p. 3456 - 3460
(2019/02/13)

B(C6F5)3-Catalyzed Deoxygenative Reduction of Amides to Amines with Ammonia Borane
The first B(C6F5)3-catalyzed deoxygenative reduction of amides into the corresponding amines with readily accessible and stable ammonia borane (AB) as a reducing agent under mild reaction conditions is reported. This metal-free protocol provides facile access to a wide range of structurally diverse amine products in good to excellent yields, and various functional groups including those that are reduction-sensitive were well tolerated. This new method is also applicable to chiral amide substrates without erosion of the enantiomeric purity. The role of BF3 ? OEt2 co-catalyst in this reaction is to activate the amide carbonyl group via the in situ formation of an amide-boron adduct. (Figure presented.).
Pan, Yixiao,Luo, Zhenli,Han, Jiahong,Xu, Xin,Chen, Changjun,Zhao, Haoqiang,Xu, Lijin,Fan, Qinghua,Xiao, Jianliang
supporting information
p. 2301 - 2308
(2019/01/30)

Ru-Catalyzed Deoxygenative Transfer Hydrogenation of Amides to Amines with Formic Acid/Triethylamine
A ruthenium(II)-catalyzed deoxygenative transfer hydrogenation of amides to amines using HCO2H/NEt3 as the reducing agent is reported for the first time. The catalyst system consisting of [Ru(2-methylallyl)2(COD)], 1,1,1-tris(diphenylphosphinomethyl) ethane (triphos) and Bis(trifluoromethane sulfonimide) (HNTf2) performed well for deoxygenative reduction of various secondary and tertiary amides into the corresponding amines in high yields with excellent selectivities, and exhibits high tolerance toward functional groups including those that are reduction-sensitive. The choice of hydrogen source and acid co-catalyst is critical for catalysis. Mechanistic studies suggest that the reductive amination of the in situ generated alcohol and amine via borrowing hydrogen is the dominant pathway. (Figure presented.).
Pan, Yixiao,Luo, Zhenli,Xu, Xin,Zhao, Haoqiang,Han, Jiahong,Xu, Lijin,Fan, Qinghua,Xiao, Jianliang
supporting information
p. 3800 - 3806
(2019/07/12)

STABILIZATION OF ACTIVE METAL CATALYSTS AT METAL-ORGANIC FRAMEWORK NODES FOR HIGHLY EFFICIENT ORGANIC TRANSFORMATIONS
Metal-organic framework (MOFs) compositions based on post?synthetic metalation of secondary building unit (SBU) terminal or bridging OH or OH2 groups with metal precursors or other post-synthetic manipulations are described. The MOFs provide a versatile family of recyclable and reusable single-site solid catalysts for catalyzing a variety of asymmetric organic transformations, including the regioselective boryiation and siiylation of benzyiic C—H bonds, the hydrogenation of aikenes, imines, carbonyls, nitroarenes, and heterocycles, hydroboration, hydrophosphination, and cyclization reactions. The solid catalysts can also be integrated into a flow reactor or a supercritical fluid reactor.
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Paragraph 0349

(2019/01/07)

Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation
Titania (TiO2) is widely used in the chemical industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying molecular mechanism is not understood due to the presence of multiple catalytic species on the TiO2 surface. This challenge can be addressed with metal-organic frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti8(μ2-O)8(μ2-OH)4 node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO2 support to enable CoII-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported CoII-hydride is strongly dependent on the reduction of the Ti-oxo cluster, definitively proving the pivotal role of TiIII in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understating the strong metal-support interaction of TiO2-supported heterogeneous catalysts.
Ji, Pengfei,Song, Yang,Drake, Tasha,Veroneau, Samuel S.,Lin, Zekai,Pan, Xiandao,Lin, Wenbin
p. 433 - 440
(2018/01/17)

Secondary amine salt catalyzed controlled activation of 2-deoxy sugar lactols towards alpha-selective dehydrative glycosylation
A new organocatalytic glycosylation method exploiting the lactol functionality has been disclosed. The catalytic generation of glycosyl oxacarbenium ions from lactols under forcible conditions via weakly Br?nsted-acidic, readily available secondary amine salts affects the diastereoselective glycosylation of 2-deoxypyranoses and furanoses. This operationally simple iminium catalyzed activation of 2-deoxy hemi-acetals is a potential alternative to the existing cumbersome methods that need specialized handling. The mechanisms for this unique transformation and kinetic/thermodynamic effects have been discussed based on both experimental evidence and theoretical studies.
Ghosh, Titli,Mukherji, Ananya,Srivastava, Hemant Kumar,Kancharla, Pavan K.
supporting information
p. 2870 - 2875
(2018/05/03)

Aerobic oxidative dehydrogenation of N-heterocycles catalyzed by cobalt porphyrin
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
supporting information
p. 949 - 953
(2018/02/09)

Sustainable Radical Cascades to Synthesize Difluoroalkylated Pyrrolo[1,2-a]indoles
We disclose herein a photocatalytic difluoroalkylation and cyclization cascade reaction of N-(but-2-enoyl)indoles with broad substrate scopes in up to 90% isolated yield. This method provides sustainable and efficient access to synthesize difluoroalkylated pyrrolo[1,2-a]indoles with a quaternary carbon center under mild conditions.
Huang, Honggui,Yu, Menglin,Su, Xiaolong,Guo, Peng,Zhao, Jia,Zhou, Jiabing,Li, Yi
p. 2425 - 2437
(2018/02/23)

Ru(ii)-Catalyzed C7-acyloxylation of indolines with carboxylic acids
Ruthenium(ii)-catalyzed site-selective C7-acyloxylation of indolines with carboxylic acids is presented. The substrate scope and functional group tolerance are important practical features. The kinetic isotope studies suggest that C-H bond activation may be the rate-determining step.
De, Pinaki Bhusan,Banerjee, Sonbidya,Pradhan, Sourav,Punniyamurthy, Tharmalingam
p. 5889 - 5898
(2018/08/21)

Expedient cobalt(II)-catalyzed site-selective C7-arylation of indolines with arylboronic acids
Cobalt(ii)-catalyzed pyrimidyl directing group-assisted C7 arylation of indolines with arylboronic acids has been developed using Mn(OAc)2·4H2O as an oxidant. The use of cobalt(ii)-PCy3 as a catalyst and broad substrate scope are the important practical features.
De, Pinaki Bhusan,Pradhan, Sourav,Banerjee, Sonbidya,Punniyamurthy, Tharmalingam
supporting information
p. 2494 - 2497
(2018/03/21)

Facile hydrogenation of N-heteroarenes by magnetic nanoparticle-supported sub-nanometric Rh catalysts in aqueous medium
The hydrogenation of nitrogen-containing heterocyclic precursors in aqueous medium at low temperature without imposing molecular hydrogen pressure is quite challenging. Herein, we report the synthesis and performance of a novel catalyst capable of facile hydrogenation (employing tetrahydroxydiboron (THDB) as the reductant) of N-heteroarenes in water at 80 °C with good recyclability. Rhodium particles in the sub-nano range (3O4), using aqueous ammonia as a reducing agent at 50 °C. HRTEM and elemental mapping images reveal a homogeneous distribution of 3O4 nanoparticles having an average size within a narrow range of 7-9 nm. The superparamagnetic nature of the composite was confirmed by VSM analysis. The Rh@Fe3O4 catalyst was found to be highly efficient in the heterogeneous hydrogenation of nitrogen-containing heterocyclic compounds with quantitative conversion. It showed selectivity towards the hydrogenation of 1,2,3,4-tetrahydroquinoline (py-THQ) in water using THDB with a high TOF of 1632 h-1. These results are compared with the conversion and selectivity data obtained from reduction with molecular hydrogen gas pressure. The catalytic activity is extended to the successful hydrogenation of simple aromatics like benzene, toluene etc. Isotopic labelling studies were performed to determine the source of hydrogen in quinoline hydrogenation in the presence of THDB. It was found that it could be used for 16 consecutive cycles with gaseous hydrogen, without any undesired by-products; it also retained its original crystallinity.
Nasiruzzaman Shaikh,Aziz, Md. Abdul,Kalanthoden, Abdul Nasar,Helal, Aasif,Hakeem, Abbas S.,Bououdina, Mohamed
p. 4709 - 4717
(2018/09/29)