- Sulfated polyborate: A dual catalyst for the reductive amination of aldehydes and ketones by NaBH4
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An efficient, quick, and environment-friendly one-pot reductive amination of aldehydes or ketones was developed. In ethanol at 70 °C, a imination catalyzed by sulfated polyborate and further reduced by sodium borohydride yields various amines. The present method has many significant benefits, including a shorter reaction time, excellent yields, and a hassle-free, straightforward experimental process. The reaction has a wide range of applications due to its flexibility, including secondary amine for reductive amination.
- Ganwir, Prerna,Chaturbhuj, Ganesh
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supporting information
(2021/05/19)
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- Novel and facile synthesis of 1-benzazepines via copper-catalyzed oxidative C(sp3)-H/C(sp2)-H cross-coupling
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A novel and facile synthetic strategy for the construction of 1-benzazepines has been developed via copper-catalyzed oxidative C(sp3)-H/C(sp2)-H cross-coupling directly from two inert C-H bonds. This transformation represents an atom- and step-economical way to synthesize biologically important seven-membered benzo-heterocycles compared with the known methods.
- Wang, Rui,Jin, Ruo-Xing,Qin, Zi-Yang,Bian, Kang-Jie,Wang, Xi-Sheng
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supporting information
p. 12229 - 12232
(2017/11/16)
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- Synthesis of 3-acetyl-4-hydroxy-1-phenylpyridin-2(1H)-one derivatives
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The cyclization of aryl ketone anilides 3 with diethyl malonate to affords 4-hydroxy-6-phenyl-6H-pyrano [3,2-c]-pyridin-2,5-diones 4 in good yields. 3-Acetyl-4-hydroxy-1-phenylpyridin-2(1H)-ones 5 are obtained by ring-opening reaction of 4-hydroxy-6-pheny
- Nikam,Kappe
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p. 215 - 220
(2015/01/30)
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- Rationally-designed S-chiral bissulfinamides as highly enantioselective organocatalysts for reduction of ketimines
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We recently reported the first example of S-chiral organocatalysts, that are highly efficient and enantioselective in substoichometric amounts, and which use a chiral monosulfinamide group as Lewis base to activate trichlorosilane (HSiCl3) to reduce N-arylketimines. Aplausible mechanism involving two molecules of the monosulfinamde catalyst for the activation of HSiCl 3 prompted us to design S-chiral bissulfinamides as new catalysts. We herein describe our findings that an easily prepared S-chiral bissulfinamide bearing a five-methylene linkage not only inherited the excellent substrate generality from the monosulfinamide catalysts, but also exhibited further improved enantioselectivity.
- Pei, Dong,Zhang, Yu,Wei, Siyu,Wang, Meng,Sun, Jian
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supporting information; experimental part
p. 619 - 623
(2009/04/21)
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- Efficient ruthenium-catalyzed aerobic oxidation of amines by using a biomimetic coupled catalytic system
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Efficient aerobic oxidation of amines was developed by the use of a biomimetic coupled catalytic system involving a ruthenium-induced dehydrogenation. The principle for this aerobic oxidation is that the electron transfer from the amine to molecular oxygen occurs stepwise via coupled redox systems and this leads to a low-energy electron transfer. A substrate-selective ruthenium catalyst dehydrogenates the amine and the hydrogen atoms abstracted are transported to an electron-rich quinone (2a). The hydroquinone thus formed is subsequently reoxidized by air with the aid of an oxygen-activating [Co(salen)]-type complex (27). The reaction can be used for the preparation of ketimines and aldimines in good to high yields from the appropriate corresponding amines. The reaction proceeds with high selectivity, and the catalytic system tolerates air without being deactivated. The rate of the dehydrogenation was studied by using quinone 2a as the terminal oxidant. A catalytic cycle in which the amine promotes the dissociation of the dimeric catalyst 1 is presented.
- Samec, Joseph S. M.,Ell, Alida H.,Baeckvall, Jan-E.
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p. 2327 - 2334
(2007/10/03)
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- Ruthenium-catalyzed transfer hydrogenation of imines by propan-2-ol in benzene
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Transfer hydrogenation of a variety of different imines to the corresponding amines by propan-2-ol in benzene catalyzed by [Ru2(CO)4(μ H)(C4Ph4COHOCC4Ph4)] (1) has been studied. The reaction is highly efficient with turnover frequencies of over 800 per hour, and the product amines were obtained in excellent yields. A remarkable concentration dependence of propan-2-ol was observed when the reaction was run in benzene as cosolvent. An optimum was obtained at 24 equivalents of propan-2-ol to imine, and further increase of the propan-2-ol led to a dramatic decrease in rate. Also the use of polar cosolvents with 24 equivalents of propan-2-ol gave a low rate. It was found that ketimines react faster than aldimines and that electron-donating substituents on the imine increase the rate of the catalytic transfer hydrogenation. Electron-withdrawing substituents decreased the rate. An isomerization was observed with imines having an α-hydrogen at the N-alkyl substituent, which is in accordance with a mechanism involving a ruthenium-amine intermediate. It was demonstrated that the ruthenium-amine complex from α-methylbenzylamine, corresponding to the postulated intermediate, can replace 1 as catalyst in the transfer hydrogenation of imines. A primary deuterium isotope effect of kCH/CD = 2.7 ± 0.25 was observed when 2-deuterio-propan-2-ol vas used in place of propan-2-ol in the ransfer hydrogenation of N-phenyl-(1-phenylethylidene)amine.
- Samec, Joseph S. M.,Baeckvall, Jan-E.
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p. 2955 - 2961
(2007/10/03)
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