- Rhodium-catalyzed transfer hydrogenation of quinoxalines with water as a hydrogen source
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Rhodium-catalyzed transfer hydrogenation of quinoxalines with water as a hydrogen source was reported. The reaction allowed the simple preparation of tetrahydroquinoxalines under mild conditions. The deuterium-labelling experiment confirmed that water is
- Zhang, Xia,Chen, Jingchao,Khan, Ruhima,Shen, Guoli,He, Zhenxiu,Zhou, Yongyun,Fan, Baomin
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p. 10142 - 10147
(2019/12/26)
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- Cobalt-bridged secondary building units in a titanium metal-organic framework catalyze cascade reduction of N-heteroarenes
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We report here a novel Ti3-BPDC metal-organic framework (MOF) constructed from biphenyl-4,4′-dicarboxylate (BPDC) linkers and Ti3(OH)2 secondary building units (SBUs) with permanent porosity and large 1D channels. Ti-OH groups from neighboring SBUs point toward each other with an O-O distance of 2 ?, and upon deprotonation, act as the first bidentate SBU-based ligands to support CoII-hydride species for effective cascade reduction of N-heteroarenes (such as pyridines and quinolines) via sequential dearomative hydroboration and hydrogenation, affording piperidine and 1,2,3,4-tetrahydroquinoline derivatives with excellent activity (turnover number ~ 1980) and chemoselectivity.
- Feng, Xuanyu,Song, Yang,Chen, Justin S.,Li, Zhe,Chen, Emily Y.,Kaufmann, Michael,Wang, Cheng,Lin, Wenbin
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p. 2193 - 2198
(2019/02/20)
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- Iridium-catalyzed condensation of amines and vicinal diols to substituted piperazines
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A straightforward procedure is described for the synthesis of piperazines from amines and 1,2-diols. The heterocyclization is catalyzed by [Cp*IrCl2]2 and sodium hydrogen carbonate and can be achieved with either toluene or water as solvent. The transformation does not require any stoichiometric additives and only produces water as the byproduct. The reaction can be performed between a 1,2-diamine and a 1,2-diol or by a double condensation between a primary alkylamine and a 1,2-diol. At least one substituent is required on the piperazine ring to achieve the cyclization in good yield. The mechanism is believed to involve dehydrogenation of the 1,2-diol to the α-hydroxy aldehyde, which condenses with the amine to form the α-hydroxy imine. The latter rearranges to the corresponding α-amino carbonyl compound, which then reacts with another amine followed by reduction of the resulting imine. Piperazines are prepared by [Cp*IrCl 2]2-catalyzed heterocyclization of 1,2-diols with either 1,2-diamines or primary alkylamines. The reaction is performed in toluene or water and requires no stoichiometric additive. The key step in the mechanism is believed to be the isomerization of an α-hydroxy imine to the corresponding α-amino carbonyl compound. Copyright
- Lorentz-Petersen, Linda L. R.,Nordstrom, Lars Ulrik,Madsen, Robert
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p. 6752 - 6759
(2013/01/15)
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