- Transformations of 1-(2-Aminophenyl)propan-2-ol to 2-Methylindoline
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The transformation reaction of 1-(2-aminophenyl)propan-2-ol was studied at 200 °C under argon pressure. A range of catalysts was applied including carbon, titania and zeolite supported Ru, Pd, Pt, Rh, and Ir, as well as metal free zeolites. The highest conversion was obtained with H-Beta-150 and H-Beta-25 and the highest selectivity to 2-methylindoline was achieved with 0.3 % Ir-H-Beta-150 and H-Beta-25. Although the selectivity to 2-methylindole was high for all catalysts, formation of the final product 2-methylindoline only took place over the most acidic catalysts.
- Bernas, Heidi,Demidova, Yuliya S.,Aho, Atte,Simakova, Irina L.,Kumar, Narendra,Laribi, Yosra,Perrichon, Philippe,Leino, Reko,Murzin, Dmitry Yu.
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- Pd/C-Catalyzed transfer hydrogenation ofN-H indoles with trifluoroethanol and tetrahydroxydiboron as the hydrogen source
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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
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supporting information
p. 548 - 551
(2021/02/06)
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- Palladium-Catalyzed Direct and Specific C-7 Acylation of Indolines with 1,2-Diketones
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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
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supporting information
p. 410 - 415
(2021/01/26)
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- Palladium supported on magnesium hydroxyl fluoride: An effective acid catalyst for the hydrogenation of imines and N-heterocycles
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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.
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supporting information
p. 19572 - 19583
(2021/11/04)
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- 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
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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
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- Aerobic Dehydrogenation of N-Heterocycles with Grubbs Catalyst: Its Application to Assisted-Tandem Catalysis to Construct N-Containing Fused Heteroarenes
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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
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supporting information
p. 15793 - 15798
(2020/10/12)
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- Catalytic reduction of aromatic ring in aqueous medium
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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)
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- Asymmetric Transfer Hydrogenation of N-Unprotected Indoles with Ammonia Borane
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A metal-free asymmetric transfer hydrogenation of unprotected indoles was successfully realized using a catalyst derived from HB(C6F5)2 and (S)-tert-butylsulfinamide with ammonia borane as a hydrogen source. A variety of indolines were achieved in 40-78percent yields with up to 90percent ee.
- Zhao, Weiwei,Zhang, Zijia,Feng, Xiangqing,Yang, Jing,Du, Haifeng
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supporting information
p. 5850 - 5854
(2020/08/05)
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- Phyllosilicate-derived Nickel-cobalt Bimetallic Nanoparticles for the Catalytic Hydrogenation of Imines, Oximes and N-heteroarenes
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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
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p. 4652 - 4663
(2020/08/19)
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- CuH-Catalyzed Enantioselective Alkylation of Indole Derivatives with Ligand-Controlled Regiodivergence
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Enantioenriched molecules bearing indole-substituted stereocenters form a class of privileged compounds in biological, medicinal, and organic chemistry. Thus, the development of methods for asymmetric indole alkylation is highly valuable in organic synthesis. Traditionally, achieving N-selectivity in indole alkylation reactions is a significant challenge, since there is an intrinsic preference for alkylation at C3, the most nucleophilic position. Furthermore, selective and predictable access to either N- or C3-alkylated chiral indoles using catalyst control has been a long-standing goal in indole functionalization. Herein, we report a ligand-controlled regiodivergent synthesis of N- and C3-alkylated chiral indoles that relies on a polarity reversal strategy. In contrast to conventional alkylation reactions in which indoles are employed as nucleophiles, this transformation employs electrophilic indole derivatives, N-(benzoyloxy)indoles, as coupling partners. N- or C3-alkylated indoles are prepared with high levels of regio- and enantioselectivity using a copper hydride catalyst. The regioselectivity is governed by the use of either DTBM-SEGPHOS or Ph-BPE as the supporting ligand. Density functional theory (DFT) calculations are conducted to elucidate the origin of the ligand-controlled regiodivergence.
- Ye, Yuxuan,Kim, Seoung-Tae,Jeong, Jinhoon,Baik, Mu-Hyun,Buchwald, Stephen L.
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supporting information
p. 3901 - 3909
(2019/03/12)
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- Re-Catalyzed Annulations of Weakly Coordinating N-Carbamoyl Indoles/Indolines with Alkynes via C?H/C?N Bond Cleavage
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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
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supporting information
p. 8245 - 8248
(2019/05/28)
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- Sodium Triethylborohydride-Catalyzed Controlled Reduction of Unactivated Amides to Secondary or Tertiary Amines
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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
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- Sodium Triethylborohydride-Catalyzed Controlled Reduction of Unactivated Amides to Secondary or Tertiary Amines
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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
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p. 14627 - 14635
(2019/12/02)
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- Expedient cobalt(II)-catalyzed site-selective C7-arylation of indolines with arylboronic acids
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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
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supporting information
p. 2494 - 2497
(2018/03/21)
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- Ru(ii)-Catalyzed C7-acyloxylation of indolines with carboxylic acids
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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
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p. 5889 - 5898
(2018/08/21)
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- Facile hydrogenation of N-heteroarenes by magnetic nanoparticle-supported sub-nanometric Rh catalysts in aqueous medium
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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
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p. 4709 - 4717
(2018/09/29)
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- Group 4 Complexes Bearing Pyrrolide Ligand for Intramolecular Alkene Hydroamination and Activation of C≡N Bond
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Titanium and zirconium complexes supported by a pyrrolide ligand HL1 [HL1 = 2-cyano-1H-pyrrole], Ti2(L2)2(NMe2)2 (1) and Zr3(L2)3(NMe2)6 (2) [L2 = N,N-dimethyl-1H-pyrrol-2-carboximidamide, NMe2-L1] were synthesized and characterized. The ligand L2 was generated by activation of C≡N bond of HL1 with HNMe2. In complex 1, two TiIV atoms are bridged by two nitrogen atoms. There are three characteristic ZrIV ions in 2, which are six-, seven- and six-coordinate, respectively. They were tested as catalysts for the intramolecular hydroamination of aminoalkenes, and the respective N-heterocycles were afforded in 74–99 % yields. Moreover, the formation of L2 ligand indicates that the amination of C≡N bond can be considered as a new and rapid way to synthesize other C–N bonds.
- Jiang, Zhilei,Wang, Yalan,Liu, Wei,Li, Yahong
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p. 844 - 848
(2018/08/24)
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- Preparation method of 2-methylindoline
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The invention belongs to the field of chemical intermediates, and particularly relates to a preparation method of 2-methylindoline. According to the preparation method, beta-methyl nitrostyrene is taken as a raw material, Raney nickel serves as a catalytic hydrogenation reductant, and the 2-methylindoline is prepared under the action of halogenated sub copper and alkali through hydrogenation reduction and intramolecular cyclization. The preparation method has the advantages of easiness in acquisition of raw materials, high reaction selectivity, purity and yield, mild reaction condition, easiness in product separation, high environment friendliness and the like, thereby being applicable to industrial production.
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Paragraph 0027-0029; 0033-0035; 0039-0044
(2018/08/28)
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- Mononuclear complexes of a tridentate redox-active ligand with sulfonamido groups: Structure, properties, and reactivity
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The design of molecular complexes of earth-abundant first-row transition metals that can catalyze multi-electron C-H bond activation processes is of interest for achieving efficient, low-cost syntheses of target molecules. To overcome the propensity of these metals to perform single-electron processes, redox-active ligands have been utilized to provide additional electron equivalents. Herein, we report the synthesis of a novel redox active ligand, [ibaps]3-, which binds to transition metals such as FeII and CoII in a meridional fashion through the three anionic nitrogen atoms and provides additional coordination sites for other ligands. In this study, the neutral bidentate ligand 2,2′-bipyridine (bpy) was used to complete the coordination spheres of the metal ions and form NEt4[MII(ibaps)bpy] (M = Fe (1) or Co (1-Co)) salts. The FeII salt exhibited rich electrochemical properties and could be chemically oxidized by 1 and 2 equiv. of ferrocenium to form singly and doubly oxidized species, respectively. The reactivity of 1 towards intramolecular C-H bond amination of aryl azides at benzylic and aliphatic carbon centers was explored, and moderate to good yields of the resulting indoline products were obtained.
- Cook, Sarah A.,Bogart, Justin A.,Levi, Noam,Weitz, Andrew C.,Moore, Curtis,Rheingold, Arnold L.,Ziller, Joseph W.,Hendrich, Michael P.,Borovik
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p. 6540 - 6547
(2018/08/16)
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- B(C6F5)3-Promoted hydrogenations of N-heterocycles with ammonia borane
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A transition-metal-free method for the B(C6F5)3-promoted hydrogenations of N-heterocycles using ammonia borane under mild reaction conditions has been developed. The reaction affords a broad range of hydrogenated products in moderate to good yields. The enantioselective versions for the corresponding products were also investigated via our approach, showing good feasibility.
- Ding, Fangwei,Zhang, Yiliang,Zhao, Rong,Jiang, Yanqiu,Bao, Robert Li-Yuan,Lin, Kaifeng,Shi, Lei
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supporting information
p. 9262 - 9264
(2017/08/21)
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- Using weak interactions to control C-H mono-nitration of indolines
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An unprecedented C-H mononitration of indolines either at the -C5 or -C7 positions under mild condition is reported here. The roles of multiple weak interactions and factors such as steric factors, electronic effects, cation-π interactions, and solvent polarity were established, and we achieved a 100% regioselective electrophilic aromatic (EArS) nitration using Cu(NO3)2 or AgNO3.
- Bose, Anima,Mal, Prasenjit
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supporting information
p. 11368 - 11371
(2017/10/19)
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- Novel nonmetal catalytic bidirectional selective reduction method of tertiary aromatic amide
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The invention relates to a novel effective bidirectional selective environment-friendly method for hydrosilation reduction of tertiary aromatic amide and an organic silicon reagent. The method comprises the following steps: selecting a nonmetal catalytic system, and selectively preparing a secondary or tertiary organic amine compound by successively catalyzing tertiary aromatic amide and cheap PHMS or triethoxysilane under a mild condition. By adopting the method, the bidirectional selective reduction of the tertiary aromatic amide is realized by innovatively utilizing an electronic effect and steric hindrance difference of an organic silicon reagent at first time, so that a brand new strategy is provided for the reduction of amide and derivative of the amide, the defects of the traditional method that the substrate functional group is poor in compatibility, the production cost is high and the like can be overcome, and the application prospect of the amine compound prepared in industrial production or laboratory is promising.
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Paragraph 0090; 0091; 0092; 0093
(2017/10/22)
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- Iron-Catalyzed Intramolecular Aminations of C(sp3)?H Bonds in Alkylaryl Azides
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The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) catalyzes the direct intramolecular amination of unactivated C(sp3)?H bonds in alkylaryl azides, which results in the formation of substituted indoline and tetrahydroquinoline derivatives.
- Alt, Isabel T.,Guttroff, Claudia,Plietker, Bernd
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supporting information
p. 10582 - 10586
(2017/08/22)
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- Rh(III)-Catalyzed C7-Thiolation and Selenation of Indolines
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The rhodium(III)-catalyzed intermolecular C7-thiolation and selenation of indolines with disulfides and diselenides were developed. This protocol relies on the use of a removable pyrimidyl directing group to access valuable C-7 functionalized indoline scaffolds with ample substrate scope and broad functional group tolerance.
- Xie, Wucheng,Li, Bin,Wang, Baiquan
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p. 396 - 403
(2016/01/25)
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- Frustrated Lewis Pair Catalyzed Dehydrogenative Oxidation of Indolines and Other Heterocycles
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An acceptorless dehydrogenation of heterocycles catalyzed by frustrated Lewis pairs (FLPs) was developed. Oxidation with concomitant liberation of molecular hydrogen proceeded in high to excellent yields for N-protected indolines as well as four other substrate classes. The mechanism of this unprecedented FLP-catalyzed reaction was investigated by mechanistic studies, characterization of reaction intermediates by NMR spectroscopy and X-ray crystal analysis, and by quantum-mechanical calculations. Hydrogen liberation from the ammonium hydridoborate intermediate is the rate-determining step of the oxidation. The addition of a weaker Lewis acid as a hydride shuttle increased the reaction rate by a factor of 2.28 through a second catalytic cycle.
- Maier, Alexander F. G.,Tussing, Sebastian,Schneider, Tobias,Fl?rke, Ulrich,Qu, Zheng -Wang,Grimme, Stefan,Paradies, Jan
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supporting information
p. 12219 - 12223
(2016/10/13)
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- METHOD FOR PRODUCING OPTICALLY ACTIVE COMPOUND, AND NOVEL METAL-DIAMINE COMPLEX
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The present invention pertains to a method for producing an optically active compound which includes a step for reducing an imino group of an imine compound or a step for reducing an unsaturated bond of a heterocyclic compound, while in the presence of hydrogen gas as a hydrogen donor and one or more types of complexes selected from a group consisting of a complex represented by general formula (1), a complex represented by general formula (2), a complex represented by general formula (3), and a complex represented by general formula (4) (the general formulas (1)-(4) are as stipulated by claim 1).
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Paragraph 0202; 0203; 0204; 0205; 0206; 0207; 0208; 0209
(2016/12/22)
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- CCC-NHC Pincer Zr Diamido Complexes: Synthesis, Characterisation, and Catalytic Activity in Hydroamination/Cyclisation of Unactivated Amino-Alkenes,-Alkynes, and Allenes
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2-(1,3-Bis-3′-butylimidazol-1′-yl-2′-ylidene)phenylene)bis(dimethylamido) iodo zirconium(iv) (3) and 2-(1,3-bis-3′-butylimidazol-1′-yl-2′-ylidene)phenylene)bis (dimethylamido) bromo zirconium(iv) (4), have been prepared via a modification of the solvent and stoichiometry from the previously reported methodology. The reactivity of 3 and 4 in hydroamination/cyclisation is reported. Both diamido complexes have been found to improve catalytic activity as compared with the previously reported mono-amido analogues. Complexes 3 and 4 were observed to be selective for primary amines over secondary amines in hydroamination/cyclisation. The lack of reactivity with secondary amines is consistent with a mechanism involving requisite formation of a Zr-imido intermediate.
- Valle, Henry U.,Akurathi, Gopalakrishna,Cho, Joon,Clark, Wesley D.,Chakraborty, Amarraj,Hollis, T. Keith
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p. 565 - 572
(2016/06/01)
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- Intramolecular hydroamination reactions catalyzed by zirconium complexes bearing bridged bis(phenolato) ligands
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Zirconium complexes stabilized by piperazidine- and imidazolidine-bridged bis(phenolato) ligands have been synthesized and characterized. Their activities in catalyzing intramolecular hydroamination reactions have been tested and compared, which reveals the significant role that the ancillary ligands play in influencing catalytic activities. Cationic species derived from zirconium dibenzyl complexes showed good activities in catalyzing intramolecular hydroamination reactions of both primary and secondary amines, and afforded the respective N-heterocycles in 85% to 99% yields. Moreover, this catalytic system also catalyzed sequential cyclization of primary aminodienes, and generated bicyclic tertiary amines in 94-99% yields.
- Zhang, Yu,Sun, Qiu,Wang, Yaorong,Yuan, Dan,Yao, Yingming,Shen, Qi
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p. 10541 - 10548
(2016/02/09)
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- Iron-catalysed sequential reaction towards α-aminonitriles from secondary amines, primary alcohols and trimethylsilyl cyanide
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We have developed a one-pot iron-catalysed sequential reaction of secondary amines with primary alcohols, trimethylsilyl cyanide and TBHP under mild reaction conditions to give the corresponding α-aminonitriles.
- Shen, Hang,Hu, Liangzhen,Liu, Qing,Hussain, Muhammad Ijaz,Pan, Jing,Huang, Mingming,Xiong, Yan
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supporting information
p. 2776 - 2779
(2016/02/19)
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- A simple iridicycle catalyst for efficient transfer hydrogenation of n-heterocycles in water
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A cyclometalated iridium complex is shown to catalyse the transfer hydrogenation of various nitrogen heterocycles, including but not limited to quinolines, isoquinolines, indoles and pyridinium salts, in an aqueous solution of HCO2H/HCO2Na under mild conditions. The catalyst shows excellent functional-group compatibility and high turnover number (up to 7500), with catalyst loadings as low as 0.01 mol % being feasible. Mechanistic investigation of the quinoline reduction suggests that the transfer hydrogenation proceeds via both 1,2- and 1,4-addition pathways, with the catalytic turnover being limited by the step of hydride transfer. An easily accessible iridicycle catalyst effects the transfer hydrogenation of a wide variety of N-heterocycles in water, including quinolines, isoquinolines, indoles, quinoxalines, and pyridines. The catalyst shows excellent functional-group compatibility and high turnover number (up to 7500), even with low catalyst loadings.
- Talwar, Dinesh,Li, Ho Yin,Durham, Emma,Xiao, Jianliang
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supporting information
p. 5370 - 5379
(2015/03/30)
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- Palladium-catalyzed C-7 alkenylation of indolines using molecular oxygen as the sole oxidant
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A general and efficient method for the intermolecular direct C-7-selective C-H alkenylation of indolines using palladium(ii) as the catalyst and molecular oxygen as the sole oxidant has been developed. The reaction showed complete regio- and stereoselectivity. All products were E-isomers at the C-7 position, and no Z-isomers or other position substituted products could be detected. The approach also presented an efficient route for the synthesis of C-7 alkenylated indoles.
- Yang, Dong,Mao, Shuai,Gao, Ya-Ru,Guo, Dong-Dong,Guo, Shi-Huan,Li, Bin,Wang, Yong-Qiang
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p. 23727 - 23736
(2015/04/14)
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- Acceptorless, Reversible Dehydrogenation and Hydrogenation of N-Heterocycles with a Cobalt Pincer Catalyst
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Acceptorless, reversible dehydrogenation and hydrogenation reactions involving N-heterocycles are reported with a well-defined cobalt complex supported by an aminobis(phosphine) [PN(H)P] pincer ligand. Several N-heterocycle substrates have been evaluated under dehydrogenation and hydrogenation conditions. The cobalt-catalyzed amine dehydrogenation step, a key step in the dehydrogenation process, has been independently verified. Control studies with related cycloalkanes suggest that a direct acceptorless alkane dehydrogenation pathway is unlikely. The metal-ligand cooperativity is probed with the related [PN(Me)P] derivative of the cobalt catalyst. These results suggest a bifunctional dehydrogenation pathway and a nonbifunctional hydrogenation mechanism.
- Xu, Ruibo,Chakraborty, Sumit,Yuan, Hongmei,Jones, William D.
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p. 6350 - 6354
(2015/11/23)
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- Versatile (Pentamethylcyclopentadienyl)rhodium-2,2′-Bipyridine (Cp?Rh-bpy) Catalyst for Transfer Hydrogenation of N-Heterocycles in Water
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An investigation employing the catalytic system consisting of (pentamethylcyclopentadienyl)rhodium dichloride dimer [Cp?RhCl2]2 and 2,2′-bipyridine (bpy) for transfer hydrogenation of a variety of quinoxalines, quinoxalinones, quinolines and indoles under aqueous conditions with formate as the hydrogen source is reported. This approach provides various tetrahydroquinoxalines, dihydroquinoxalinones, tetrahydroquinolines and indolines in good to excellent yields. The activity of the catalyst towards quinoxalines and quinoxalinones is excellent, with a substrate to catalyst ratio (S/C) of 10000 being feasible. The choice of ligand is critical to the catalysis, and the aqueous phase reduction is shown to be highly pH-dependent, with acidic pH values needed for optimal reduction. The catalyst is easy to access, and the reaction is operationally simple without requiring an inert atmosphere.
- Zhang, Lingjuan,Qiu, Ruiying,Xue, Xiao,Pan, Yixiao,Xu, Conghui,Li, Huanrong,Xu, Lijin
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p. 3529 - 3537
(2016/01/25)
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- A molecular iron catalyst for the acceptorless dehydrogenation and hydrogenation of N-heterocycles
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A well-defined iron complex (3) supported by a bis(phosphino)amine pincer ligand efficiently catalyzes both acceptorless dehydrogenation and hydrogenation of N-heterocycles. The products from these reactions are isolated in good yields. Complex 3, the active catalytic species in the dehydrogenation reaction, is independently synthesized and characterized, and its structure is confirmed by X-ray crystallography. A trans-dihydride intermediate (4) is proposed to be involved in the hydrogenation reaction, and its existence is verified by NMR and trapping experiments.
- Chakraborty, Sumit,Brennessel, William W.,Jones, William D.
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supporting information
p. 8564 - 8567
(2014/07/07)
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- A general method for N-methylation of amines and nitro compounds with dimethylsulfoxide
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DMSO methylates a broad range of amines in the presence of formic acid, providing a novel, green and practical method for amine methylation. The protocol also allows the one-pot transformation of aromatic nitro compounds into dimethylated amines in the presence of a simple iron catalyst. Not just a solvent: DMSO methylates a broad range of amines in the presence of formic acid, providing a novel, green and practical method for amine methylation. The protocol also allows the one-pot transformation of aromatic nitro compounds into dimethylated amines in the presence of a simple iron catalyst. Copyright
- Jiang, Xue,Wang, Chao,Wei, Yawen,Xue, Dong,Liu, Zhaotie,Xiao, Jianliang
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supporting information
p. 58 - 63
(2014/01/17)
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- Homogenous Pd-catalyzed asymmetric hydrogenation of unprotected indoles: Scope and mechanistic studies
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An efficient palladium-catalyzed asymmetric hydrogenation of a variety of unprotected indoles has been developed that gives up to 98% ee using a strong Br?nsted acid as the activator. This methodology was applied in the facile synthesis of biologically active products containing a chiral indoline skeleton. The mechanism of Pd-catalyzed asymmetric hydrogenation was investigated as well. Isotope-labeling reactions and ESI-HRMS proved that an iminium salt formed by protonation of the C=C bond of indoles was the significant intermediate in this reaction. The important proposed active catalytic Pd-H species was observed with 1H NMR spectroscopy. It was found that proton exchange between the Pd-H active species and solvent trifluoroethanol (TFE) did not occur, although this proton exchange had been previously observed between metal hydrides and alcoholic solvents. Density functional theory calculations were also carried out to give further insight into the mechanism of Pd-catalyzed asymmetric hydrogenation of indoles. This combination of experimental and theoretical studies suggests that Pd-catalyzed hydrogenation goes through a stepwise outer-sphere and ionic hydrogenation mechanism. The activation of hydrogen gas is a heterolytic process assisted by trifluoroacetate of Pd complex via a six-membered-ring transition state. The reaction proceeds well in polar solvent TFE owing to its ability to stabilize the ionic intermediates in the Pd-H generation step. The strong Br?nsted acid activator can remarkably decrease the energy barrier for both Pd-H generation and hydrogenation. The high enantioselectivity arises from a hydrogen-bonding interaction between N-H of the iminium salt and oxygen of the coordinated trifluoroacetate in the eight-membered-ring transition state for hydride transfer, while the active chiral Pd complex is a typical bifunctional catalyst, effecting both the hydrogenation and hydrogen-bonding interaction between the iminium salt and the coordinated trifluoroacetate of Pd complex. Notably, the Pd-catalyzed asymmetric hydrogenation is relatively tolerant to oxygen, acid, and water.
- Duan, Ying,Li, Lu,Chen, Mu-Wang,Yu, Chang-Bin,Fan, Hong-Jun,Zhou, Yong-Gui
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supporting information
p. 7688 - 7700
(2014/06/10)
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- Catalytic methylation of C-H bonds using CO2 and H2
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Formation of C-C bonds from CO2 is a much sought after reaction in organic synthesis. To date, other than C-H carboxylations using stoichiometric amounts of metals, base, or organometallic reagents, little is known about C-C bond formation. In fact, to the best of our knowledge no catalytic methylation of C-H bonds using CO2 and H2 has been reported. Described herein is the combination of CO2 and H2 for efficient methylation of carbon nucleophiles such as indoles, pyrroles, and electron-rich arenes. Comparison experiments which employ paraformaldehyde show similar reactivity for the CO2/H2 system. Capturing: Carbon dioxide in the presence of H2 is shown to be an efficient methylating reagent for carbon nucleophiles such as 2-substituted indoles, pyrroles, and electron-rich arenes. Experimental data support the formal capture of formaldehyde. acac=acetylacetonate, triphos=1,1,1-tris(diphenylphosphinomethyl)ethane.
- Li, Yuehui,Yan, Tao,Junge, Kathrin,Beller, Matthias
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supporting information
p. 10476 - 10480
(2016/02/18)
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- Palladium on carbon-catalyzed one-pot N-arylindole synthesis: Intramolecular aromatic amination, aromatization, and intermolecular aromatic amination
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Indole and indoline derivatives were selectively and temperature dependently synthesized via the intramolecular cross-coupling reaction between the amino and aromatic bromine functionalities of 2-bromophenethylamine derivatives in the presence of 10% palladium on carbon (Pd/C), 1,1-bis(diphenylphosphino)ferrocene (DPPF), and sodium tert-butoxide (NaO-t-Bu) in mesitylene at 140 and 200°C, respectively. The neutralization using acetic acid after formation of the indoline derivatives effectively promoted their aromatization, and the corresponding indole derivatives were obtained at 140°C. Furthermore, various aryl groups were also introduced to the N-1 position of the indole, pyrrole, and carbazole rings by their direct intramolecular arylation with aryl halides and a one-pot protocol for N-arylindole synthesis from 2-bromophenethylamine was developed.
- Monguchi, Yasunari,Marumoto, Takahisa,Takamatsu, Haruki,Sawama, Yoshinari,Sajiki, Hironao
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supporting information
p. 1866 - 1872
(2014/06/09)
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- Robust cyclometallated Ir(iii) catalysts for the homogeneous hydrogenation of N-heterocycles under mild conditions
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Cyclometallated Cp*Ir(N∧C)Cl complexes derived from N-aryl ketimines are highly active catalysts for the reduction of N-heterocycles under ambient conditions and 1 atm H2 pressure. The reaction tolerates a broad range of other potentially reducible functionalities and does not require the use of specialised equipment, additives or purified solvent.
- Wu, Jianjun,Barnard, Jonathan H.,Zhang, Yi,Talwar, Dinesh,Robertson, Craig M.,Xiao, Jianliang
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supporting information
p. 7052 - 7054
(2013/09/02)
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- Chiral phosphoric acid-catalyzed oxidative kinetic resolution of indolines based on transfer hydrogenation to imines
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The oxidative kinetic resolution of 2-substituted indoline derivatives was achieved by hydrogen transfer to imines by means of a chiral phosphoric acid catalyst. The oxidative kinetic resolution was applicable to racemic alkyl- or aryl-substituted indolines, and the remaining indolines were obtained in good yields with excellent enantioselectivities.
- Saito, Kodai,Shibata, Yukihiro,Yamanaka, Masahiro,Akiyama, Takahiko
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supporting information
p. 11740 - 11743
(2013/09/02)
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- Rhodium(III)-catalyzed direct regioselective synthesis of 7-substituted indoles
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An efficient, atom-economic one-pot method was developed for the preparation of 7-substituted indoles via rhodium(III)-catalyzed oxidative cross-coupling. Regioselective olefination of indoline derivatives followed by one-pot subsequent oxidation provided the desired products in good to excellent yields.
- Song, Zengqiang,Samanta, Rajarshi,Antonchick, Andrey P.
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supporting information
p. 5662 - 5665
(2013/12/04)
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- Highly enantioselective zirconium-catalyzed cyclization of aminoalkenes
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Aminoalkenes are catalytically cyclized in the presence of cyclopentadienylbis(oxazolinyl)borato group 4 complexes {PhB(C5H 4)(OxR)2}M(NMe2)2 (M = Ti, Zr, Hf; OxR = 4,4-dimethyl-2-oxazoline, 4S-isopropyl-5,5- dimethyl-2-oxazoline, 4S-tert-butyl-2-oxazoline) at room temperature and below, affording five-, six-, and seven-membered N-heterocyclic amines with enantiomeric excesses of >90% in many cases and up to 99%. Mechanistic investigations of this highly selective system employed synthetic tests, kinetics, and stereochemistry. Secondary aminopentene cyclizations require a primary amine (1-2 equiv vs catalyst). Aminoalkenes are unchanged in the presence of a zirconium monoamido complex {PhB(C5H 4)(Ox4S-iPr,Me2)2}Zr(NMe2)Cl or a cyclopentadienylmono(oxazolinyl)borato zirconium diamide {Ph2B(C 5H4)(Ox4S-iPr,Me2)}Zr(NMe2) 2. Plots of initial rate versus [substrate] show a rate dependence that evolves from first-order at low concentration to zero-order at high concentration, and this is consistent with a reversible substrate-catalyst interaction preceding an irreversible step. Primary kinetic isotope effects from substrate conversion measurements (k′obs(H)/ k′obs(D) = 3.3 ± 0.3) and from initial rate analysis (k2(H)/k2(D) = 2.3 ± 0.4) indicate that a N-H bond is broken in the turnover-limiting and irreversible step of the catalytic cycle. Asymmetric hydroamination/cyclization of N-deutero-aminoalkenes provides products with higher optical purities than obtained with N-proteo-aminoalkenes. Transition state theory, applied to the rate constant k2 that characterizes the irreversible step, provides activation parameters consistent with a highly organized transition state (ΔS? = -43(7) cal·mol-1 K -1) and a remarkably low enthalpic barrier (ΔH ? = 6.7(2) kcal·mol-1). A six-centered, concerted transition state for C-N and C-H bond formation and N-H bond cleavage involving two amidoalkene ligands is proposed as most consistent with the current data.
- Manna, Kuntal,Everett, William C.,Schoendorff, George,Ellern, Arkady,Windus, Theresa L.,Sadow, Aaron D.
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supporting information
p. 7235 - 7250
(2013/06/27)
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- A novel organic electron donor derived from N-methylisatin
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We report the reactivity of an electron donor derived from N-methylisatin on reduction by sodium amalgam. Transfer of a clear supernatant solution to iodoarenes affords the products of two-electron reduction. Reductions of sulfones, activated arenesulfonamides, and Weinreb amides are also reported.
- Sword, Ryan,O'Sullivan, Steven,Murphy, John A.
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p. 314 - 322
(2013/05/08)
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- Hexafluoroisopropanol: A powerful solvent for the hydrogenation of indole derivatives. Selective access to tetrahydroindoles or cis-fused octahydroindoles
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Pd/C in HFIP was used to hydrogenate indole derivatives under relatively mild conditions, leading to potential synthetic intermediates of bioactive compounds. Depending on their substitution, tetrahydroindoles or octahydroindoles could selectively be obtained.
- Clarisse, Damien,Fenet, Bernard,Fache, Fabienne
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experimental part
p. 6587 - 6594
(2012/09/08)
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- Rh2(II)-catalyzed intramolecular aliphatic C-H bond amination reactions using aryl azides as the N-atom source
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Rhodium(II) dicarboxylate complexes were discovered to catalyze the intramolecular amination of unactivated primary, secondary, or tertiary aliphatic C-H bonds using aryl azides as the N-atom precursor. While a strong electron-withdrawing group on the nitrogen atom is typically required to achieve this reaction, we found that both electron-rich and electron-poor aryl azides are efficient sources for the metal nitrene reactive intermediate.
- Nguyen, Quyen,Sun, Ke,Driver, Tom G.
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supporting information; experimental part
p. 7262 - 7265
(2012/06/16)
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- Heterogeneous catalytic hydrogenation of unprotected indoles in water: A green solution to a long-standing challenge
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An environmentally benign procedure for the hydrogenation of unprotected indoles is described. The hydrogenation reaction is catalyzed by Pt/C and activated by p-toluenesulfonic acid in water as a solvent. The efficacy of the method is illustrated by the hydrogenation of a variety of substituted indoles to their corresponding indolines which were obtained in excellent yields.
- Kulkarni, Aditya,Zhou, Weihong,Toeroek, Bela
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supporting information; experimental part
p. 5124 - 5127
(2011/12/05)
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- Iridium-catalyzed asymmetric hydrogenation of N-protected indoles
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Chiral indolines substituted at C-2 or C-3 can be prepared in high yield and excellent enantioselectivity by asymmetric hydrogenation of N-protected indoles by using Ir catalysts with chiral N,P ligands. With less reactive substrates, the reaction had to
- Baeza, Alejandro,Pfaltz, Andreas
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supporting information; scheme or table
p. 2036 - 2039
(2010/07/05)
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- Asymmetric synthesis of iridoid derivatives using resolved 2-phenylindoline as a chiral auxiliary
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An asymmetric synthetic route to cis,cis-nepetalactol (component of the sex pheromone for the hop aphid, Phorodon humuli) is presented. 2-Phenylindoline was resolved to provide a chiral auxiliary for the cycloaddition of oxocitral. The resolution was made by chromatographic separation of the diastereomers of the urea derivative made from 2-phenylindoline and with (R)-(+)-α- methylbenzyl isocyanate, followed by reductive cleavage of the isolated diasteromers using diborane. The cycloaddition of oxocitral using (S)-2-phenylindoline yielded an enantiopure product after chromatography. Hydrolysis of the cycloaddition adduct yielded gastrolactol (3). As gastrolactol is a versatile synthon for the synthesis of iridoids, the overall procedure provides a general asymmetric route to elaborated iridoids. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
- Santangelo, Ellen M.,Liblikas, Ilme,Mudalige, Anoma,Toernroos, Karl W.,Norrby, Per-Ola,Unelius, C. Rikard
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experimental part
p. 5915 - 5921
(2009/05/27)
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- New chiral lanthanide amide ate complexes for the catalysed synthesis of scalemic nitrogen-containing heterocycles
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New chiral binaphthylamido yttrium and ytterbium ate complexes with lithium and potassium counterions have been synthesised and characterised. X-ray structures have been obtained for [Li(thf)4][Ln{(R)-C 20H12-(NC5H9)2} 2] (Ln = Yb, Y) and [K(thf)5] [Yb{(R)-C20H 12(NCH2CMe3)2}2] as isostructural complexes. The efficiency of these complexes for the enantioselective intramolecular hydroamination was examined. [Li(thf) 4][Yb{(R)-C20H12(NC5H 9)2}2] afforded the highest enantiomeric excess (up to 87%) for the synthesis of a spiropyrrolidine, while [Li(thf) 4][Y{(R)-C20H12-(NC5H 9)2}2] proved to be slightly more active. The role of the counter cation in the active catalytic species was evidenced by the comparison between lithium and potassium ate complexes. The most active catalyst of this series, [Li(thf)4][Yb{(R)-C20H 12(NCH2CMe3)2}2], was successfully used for the cyclisation of aminopentenes with internal double bonds.
- Aillaud, Isabelle,Collin, Jacqueline,Duhayon, Carine,Guillot, Regis,Lyubov, Dmitrii,Schulz, Emmanuelle,Trifonov, Alexander
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body text
p. 2189 - 2200
(2009/04/06)
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- Enhanced reactivity in OH/NH/π polyfunctional systems through coupled proton/electron transfer in the excited state: The photocyclisation of 2-allyl-3-aminophenol
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The photocyclisation rate of 2-allyl-3-(or 5-)aminophenols (1, 4 and 8) is dramatically enhanced, when compared with reference compounds, as a consequence of a coupled proton/electron transfer process. The Royal Society of Chemistry 2005.
- Leo, Edgar A.,Tormos, Rosa,Miranda, Miguel A.
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p. 1203 - 1205
(2007/10/03)
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