- Highly pH-Dependent Chemoselective Transfer Hydrogenation of α,β-Unsaturated Aldehydes in Water
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The pH-dependent selective Ir-catalyzed hydrogenation of α,β-unsaturated aldehydes was realized in water. Using HCOOH as the hydride donor at low pH, the unsaturated alcohol products were obtained exclusively, while the saturated alcohol products were formed preferentially by employing HCOONa as the hydride donor at high pH. A wide range of functional groups including electron-rich as well as electron-poor substituents on the aryl group of α,β-unsaturated aldehydes can be tolerated, affording the corresponding products in excellent yields with high TOF values. High selectivity and yields were also observed for α,β-unsaturated aldehydes with aliphatic substituents. Our mechanistic investigations indicate that the pH value is critical to the chemoselectivity.
- Luo, Nianhua,Liao, Jianhua,Ouyang, Lu,Wen, Huiling,Liu, Jitian,Tang, Weiping,Luo, Renshi
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p. 3025 - 3031
(2019/08/30)
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- Salt-Free Strategy for the Insertion of CO2 into C?H Bonds: Catalytic Hydroxymethylation of Alkynes
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A copper(I) catalyst enables the insertion of carbon dioxide into alkyne C?H bonds by using a suitable organic base with which hydrogenation of the resulting carboxylate salt with regeneration of the base becomes thermodynamically feasible. In the presence of catalytic copper(I) chloride/4,7-diphenyl-1,10-phenanthroline, polymer-bound triphenylphosphine, and 2,2,6,6-tetramethylpiperidine as the base, terminal alkynes undergo carboxylation at 15 bar CO2 and room temperature. After filtration, the ammonium alkynecarboxylate can be hydrogenated to the primary alcohol and water at a rhodium/molybdenum catalyst, regenerating the amine base. This demonstrates the feasibility of a salt-free overall process, in which carbon dioxide serves as a C1 building block in a C?H functionalization.
- Wendling, Timo,Risto, Eugen,Krause, Thilo,Goo?en, Lukas J.
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supporting information
p. 6019 - 6024
(2018/03/27)
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- New class of bioluminogenic probe based on bioluminescent enzyme-induced electron transfer: BioLeT
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Bioluminescence imaging (BLI) has advantages for investigating biological phenomena in deep tissues of living animals, but few design strategies are available for functional bioluminescent substrates. We propose a new design strategy (designated as bioluminescent enzyme-induced electron transfer: BioLeT) for luciferin-based bioluminescence probes. Luminescence measurements of a series of aminoluciferin derivatives confirmed that bioluminescence can be controlled by means of BioLeT. Based on this concept, we developed bioluminescence probes for nitric oxide that enabled quantitative and sensitive detection even in vivo. Our design strategy should be applicable to develop a wide range of practically useful bioluminogenic probes.
- Takakura, Hideo,Kojima, Ryosuke,Kamiya, Mako,Kobayashi, Eiji,Komatsu, Toru,Ueno, Tasuku,Terai, Takuya,Hanaoka, Kenjiro,Nagano, Tetsuo,Urano, Yasuteru
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supporting information
p. 4010 - 4013
(2015/04/14)
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- Selective reduction of alkenes, α,β-unsaturated carbonyl compounds, nitroarenes, nitroso compounds, N,N-hydrogenolysis of azo and hydrazo functions as well as simultaneous hydrodehalogenation and reduction of substituted aryl halides over PdMCM-41 catalyst under transfer hydrogen conditions
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Chemoselective reductions of alkenes, α,β-unsaturated carbonyl compounds, nitro and nitroso compounds, N,N-hydrogenolysis of azo and hydrazo functions as well as simultaneous reduction and hydrodehalogenation of substituted aryl halides, including bulkier substrates, were achieved by catalytic transfer hydrogenation (CTH) using mesoporous PdMCM-41 catalyst. The yields were practically unaffected upon recycling of the catalyst. Further, the CTH process is accomplished without affecting the reduction of any other reducible functional group.
- Selvam, Parasuraman,Sonavane, Sachin U.,Mohapatra, Susanta K.,Jayaram, Radha V.
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p. 3071 - 3075
(2007/10/03)
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- SYNTHESIS OF A TRIAD MOLECULAR SYSTEM CONTAINING THE PHOTOSENSITIZER MESOPORPHYRIN II AND A SECONDARY ELECTRON DONOR AND ACCEPTOR FOR MODELING THE PHOTOSYNTHESIS PROCESS
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We describe methods for synthesis of a triad molecular system based on mesoporphyrin II with electron-donor and electron-acceptor moieties for modeling the primary stage of charge separation in photosynthesis, differing in the order of addition of the donor and the acceptor.Using fluorescent spectroscopy, we have demonstrated quenching-containing coppounds.Investigation of the triad and its zinc complex by kinetic fluorescent spectroscopy allowed us to determine the electron transfer rate constants for the triad and for its zinc complex.
- Borovkov, V. V.,Evstigneeva, R. P.,Gribkov, A. A.
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p. 296 - 302
(2007/10/03)
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- Mechanism of Charge Transfer in the Molecular DPQ Complex Studied by Time-Resolved Fluorescence Spectroscopy
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The pathways of charge separation in the dimethylaniline-mesoporphyrin II-naphthoquinone triad DPQ and its Zn complex were established.The rate constants of electron transfer from P and ZnP to Q were measured to be k = 1.5x109 s-1 and k > 5x1010 s-1, respectively, from the results of picosecond fluorescence spectroscopy.The transformation of the DPQ and DZnPQ triads to the reduced form by NaBH4 treatment results in blocking of the electron-transfer channel from both P and ZnP to Q.The transformation of the DPQ and DZnPQ triads to the reduced forms by NaBH4 results in blocking of the electron-transfer channel from both P and ZnP to Q.The role of structural and conformational changes of triads in the electron-transfer process is discussed.
- Borovkov, V. V.,Evstigneeva, R. P.,Struganova, I. A.,Kamalov, V. F.,Toleutaev, B. N.
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p. 6437 - 6440
(2007/10/02)
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