- Switching Selectivity in Copper-Catalyzed Transfer Hydrogenation of Nitriles to Primary Amine-Boranes and Secondary Amines under Mild Conditions
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A simple and efficient copper-catalyzed selective transfer hydrogenation of nitriles to primary amine-boranes and secondary amines with an oxazaborolidine-BH3 complex is reported. The selectivity control was achieved under mild conditions by switching the solvent and the copper catalysts. More than 30 primary amine-boranes and 40 secondary amines were synthesized via this strategy in high selectivity and yields of up to 95%. The strategy was applied to the synthesis of 15N labeled in 89% yield.
- Song, Hao,Xiao, Yao,Zhang, Zhuohua,Xiong, Wanjin,Wang, Ren,Guo, Liangcheng,Zhou, Taigang
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p. 790 - 800
(2022/01/11)
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- Phosphine-Free Manganese Catalyst Enables Selective Transfer Hydrogenation of Nitriles to Primary and Secondary Amines Using Ammonia-Borane
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Herein we report the synthesis of primary and secondary amines by nitrile hydrogenation, employing a borrowing hydrogenation strategy. A class of phosphine-free manganese(I) complexes bearing sulfur side arms catalyzed the reaction under mild reaction conditions, where ammonia-borane is used as the source of hydrogen. The synthetic protocol is chemodivergent, as the final product is either primary or secondary amine, which can be controlled by changing the catalyst structure and the polarity of the reaction medium. The significant advantage of this method is that the protocol operates without externally added base or other additives as well as obviates the use of high-pressure dihydrogen gas required for other nitrile hydrogenation reactions. Utilizing this method, a wide variety of primary and symmetric and asymmetric secondary amines were synthesized in high yields. A mechanistic study involving kinetic experiments and high-level DFT computations revealed that both outer-sphere dehydrogenation and inner-sphere hydrogenation were predominantly operative in the catalytic cycle.
- Sarkar, Koushik,Das, Kuhali,Kundu, Abhishek,Adhikari, Debashis,Maji, Biplab
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p. 2786 - 2794
(2021/03/03)
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- Surface modification boosts exciton extraction in confined layered structure for selective oxidation reaction
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Extracting photogenerated species from bulk to surface is an essential process for gaining efficient semiconductor-based photocatalysis. However, compared with charged photogenerated carriers, neutral exciton exhibits negligible response to electric field. Accordingly, traditional strategies involving band-alignment construction for boosting directional transfer of charge carriers are impracticable for extracting bulk excitons. To this issue, we here propose that the extraction of bulk exciton could be effectively implemented by surface modification. By taking confined layered bismuth oxycarbonate (Bi2O2CO3) as an example, we highlight that the incorporation of iodine atoms on the surface could modify the micro-region electronic structure and hence lead to reduced energy of surface excitonic states. Benefiting from the energy gradient between bulk and surface excitonic states, iodine-modified Bi2O2CO3 possesses high-efficiency bulk exciton extraction, and hence exhibits promoted performance in triggering 1O2-mediated selective oxidation reaction. This work presents the positive role of surface modification in regulating excitonic processes of semiconductor-based photocatalysts. [Figure not available: see fulltext.].
- Jin, Sen,Wang, Hui,Li, Lei,Luo, Xiao,Sun, Xianshun,Zuo, Ming,Tian, Jie,Zhang, Xiaodong,Xie, Yi
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p. 1964 - 1969
(2021/10/25)
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- Selective Synthesis of Secondary Amines from Nitriles by a User-Friendly Cobalt Catalyst
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Selective hydrogenation/reductive amination of nitriles to secondary amines catalyzed by an inexpensive and user-friendly cobalt complex, (Xantphos)CoCl2, is reported. The use of (Xantphos)CoCl2 and ammonia borane (NH3?BH3) combination affords the selective reduction of nitriles to symmetrical secondary amines, whereas the employment of (Xantphos)CoCl2 and dimethylamine borane (Me2NH?BH3) along with external amines produce unsymmetrical secondary amines and tertiary amines. The general applicability of this methodology is demonstrated by the synthesis of 43 symmetrical and unsymmetrical secondary and tertiary amines bearing diverse functionalities. (Figure presented.).
- Sharma, Dipesh M.,Punji, Benudhar
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supporting information
p. 3930 - 3936
(2019/07/12)
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- Iron-Catalyzed Intramolecular C-H Amination of α-Azidyl Amides
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Iron-catalyzed intramolecular C-H amination of aliphatic azides has recently emerged as a powerful tool for the preparation of nitrogen heterocycles. This paper reports that α-azidyl amides can be converted in high efficacy to imidazolinone compounds via intramolecular C(sp3)-H amination by the action of a simple catalytic system composed of FeCl2 and a β-diketiminate ligand. The reactions provide a simple and atom-economical approach toward polysubstituted imidazolinones.
- Zhao, Xiaopeng,Liang, Siyu,Fan, Xing,Yang, Tonghao,Yu, Wei
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supporting information
p. 1559 - 1563
(2019/03/20)
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- Chemoselective hydrogenation of nitriles to primary amines catalyzed by water-soluble transition metal catalysts
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The water-soluble rhodium complex generated in situ from [Rh (COD)Cl]2 in aqueous ammonia has been revealed as a highly efficient catalyst for the hydrogenation of aromatic nitriles, to primary amines with excellent yields. The catalyst is also highly selective towards primary amines in the case of sterically hindered aliphatic nitriles. The catalytic system can also be recycled and re-used with no significant loss of activity.
- Nait Ajjou, Abdelaziz,Robichaud, André
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- Synthesis of Symmetric and Unsymmetric Secondary Amines from the Ligand-Promoted Ruthenium-Catalyzed Deaminative Coupling Reaction of Primary Amines
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The catalytic system generated in situ from the tetranuclear Ru-H complex with a catechol ligand (1/L1) was found to be effective for the direct deaminative coupling of two primary amines to form secondary amines. The catalyst 1/L1 was highly chemoselective for promoting the coupling of two different primary amines to afford unsymmetric secondary amines. The analogous coupling of aniline with primary amines formed aryl-substituted secondary amines. The treatment of aniline-d7 with 4-methoxybenzylamine led to the coupling product with significant deuterium incorporation on CH2 (18% D). The most pronounced carbon isotope effect was observed on the α-carbon of the product isolated from the coupling reaction of 4-methoxybenzylamine (C(1) = 1.015(2)). A Hammett plot was constructed from measuring the rates of the coupling reaction of 4-methoxyaniline with a series of para-substituted benzylamines 4-X-C6H4CH2NH2 (X = OMe, Me, H, F, CF3) (ρ = -0.79 ± 0.1). A plausible mechanistic scheme has been proposed for the coupling reaction on the basis of these results. The catalytic coupling method provides an operationally simple and chemoselective synthesis of secondary amine products without using any reactive reagents or forming wasteful byproducts.
- Arachchige, Pandula T. Kirinde,Lee, Hanbin,Yi, Chae S.
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p. 4932 - 4947
(2018/05/08)
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- Triazolylidene-Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal–Ligand Induced Catalytic Dehydrogenation of Amines
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Two iridium(III) complexes containing a C,N-bidentate pyridyl-triazolylidene ligand were prepared that are structurally very similar but differ in their pendant substituent. Whereas complex 1 contains a non-coordinating pyridyl unit, complex 2 has a phenyl group on the triazolylidene substituent. The presence of the basic pyridyl unit has distinct effects on the catalytic activity of the complex in the oxidative dehydrogenation of benzylic amines, inducing generally higher rates, higher selectivity towards formation of imines versus secondary amines, and notable quantities of tertiary amines when compared to the phenyl-functionalized analogue. The role of the pyridyl functionality has been elucidated from a set of stoichiometric experiments, which demonstrate hydrogen bonding between the pendant pyridyl unit and the amine protons of the substrate. Such Npyr???H?N interactions are demonstrated by X-ray diffraction analysis, 1H NMR, and IR spectroscopy, and suggest a pathway of substrate bond-activation that involves concerted substrate binding through the Lewis acidic iridium center and the Lewis basic pyridyl site appended to the triazolylidene ligand, in agreement with ligand–metal cooperative substrate activation.
- Valencia, Marta,Pereira, Ana,Müller-Bunz, Helge,Belderraín, Tomás R.,Pérez, Pedro J.,Albrecht, Martin
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p. 8901 - 8911
(2017/07/11)
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- C70 as a Photocatalyst for Oxidation of Secondary Benzylamines to Imines
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Photosensitive C70 was used for the catalytic oxidation of benzylamines to the corresponding imines. The advantages of using C70 compared to C60 or other commonly used photosensitizers such as tetraphenylporphyrin (TPP) ar
- Kumar, Rakesh,Glei?ner, Eva H.,Tiu, Elisha Gabrielle V.,Yamakoshi, Yoko
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supporting information
p. 184 - 187
(2016/02/05)
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- Shvo's catalyst and [IrCp7z.ast;Cl2(amidine)] effectively catalyze the formation of tertiary amines from the reaction of primary alcohols and ammonium salts
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The reaction of (pentamethylcyclopentadienyl)iridium dichloride dimer, [IrCp*Cl2]2, with bis(2,4,6-trimethylphenyl) formamidine allows the preparation of two new [IrCp*Cl 2(amidine)] and [IrCp*Cl(amidinate)] complexes, which have been fully characterized. Both complexes have been tested in the β-alkylation of 1-phenylethanol with primary alcohols, and in the formation of tertiary amines from the reaction of ammonium salts with primary alcohols, and the results have been compared with those shown by Shvo's catalyst. Our studies demonstrate that both [IrCp*Cl2(amidine)] and Shvo's catalyst are very efficient in both catalytic processes. The high activity of the Ir-amidine complex may be attributed to the presence of the NH group in the amidine ligand. Copyright
- Segarra, Candela,Mas-Marza, Elena,Mata, Jose A.,Peris, Eduardo
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experimental part
p. 2078 - 2084
(2011/10/11)
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- Highly chemoselective reductive amination-coupling by one-pot reaction of aldehydes, HMDS and NaBH4
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An efficient and highly chemoselective synthesis of symmetrical secondary amines via reductive amination of aldehydes with inexpensive and commercially available HMDS and sodium borohydride in high to quantitative yields is reported.
- Azizi, Najmedin,Akbari, Elham,Amiri, Alireza Khejeh,Saidi, Mohammad R.
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scheme or table
p. 6682 - 6684
(2009/04/06)
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- Hammett correlations 'beyond the molecule'
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The crown ether dibenzo[24]crown-8 (DB24C8) is interpenetrated by a wide range of disubstituted dibenzylammonium cations to generate [2]pseudorotaxane complexes by virtue of, inter alia, hydrogen bonds. 1H NMR spectroscopic measurements indicat
- Ashton, Peter R.,Fyfe, Matthew C.T.,Hickingbottom, Sarah K.,Stoddart, J. Fraser,White, Andrew J. P.,Williams, David J.
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p. 2117 - 2128
(2007/10/03)
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