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Long Zhang - One of the best experts on this subject based on the ideXlab platform.
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enantioselective terminal addition to allenes by dual chiral Primary Amine palladium catalysis
Journal of the American Chemical Society, 2017Co-Authors: Han Zhou, Yaning Wang, Long ZhangAbstract:We herein describe a synergistic chiral Primary Amine/achiral palladium catalyzed enantioselective terminal addition to allenes with α-branched β-ketocarbonyls and aldehydes. The reactions afford allylic adducts bearing acyclic all-carbon quaternary centers with high regio- and enantioselectivity. A wide range of allenes including those aliphatic or 1,1′-disubstituted could be employed, thus expanding the scope of typical asymmetric allylic alkylation reactions.
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reagent controlled enantioselectivity switch for the asymmetric fluorination of β ketocarbonyls by chiral Primary Amine catalysis
Chemical Science, 2017Co-Authors: Yangen You, Long Zhang, Sanzhong LuoAbstract:A reagent-controlled enantioselectivity switch was uncovered in the asymmetric α-fluorination of β-ketocarbonyls by a chiral Primary Amine catalyst. By a simple swap of fluorination reagents, both enantiomers of the quaternary fluorination adducts could be obtained with good yields and high enantioselectivity. Mechanistic studies disclosed dual H-bonding and electrostatic stereocontrolling modes for the catalysis.
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asymmetric retro claisen reaction by chiral Primary Amine catalysis
Journal of the American Chemical Society, 2016Co-Authors: Long ZhangAbstract:The communication describes an enAmine-based asymmetric retro-Claisen reaction of β-diketones by Primary Amine catalysis. The reaction proceeds via a sequence of stereoselective C–C formation, C–C cleavage, and a highly stereospecific enAmine protonation to afford chiral α-alkylated ketones or macrolides with high yields and enantioselectivities. A detailed mechanism was explored on the basis of experimental evidence and computational studies to account for the observed stereocontrol.
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chiral Primary Amine palladium dual catalysis for asymmetric allylic alkylation of β ketocarbonyl compounds with allylic alcohols
Angewandte Chemie, 2015Co-Authors: Han Zhou, Long Zhang, Changming XuAbstract:An efficient dual catalytic system composed of a chiral Primary Amine and a palladium complex was developed to promote the direct asymmetric allylic alkylation (AAA) of beta-ketocarbonyl compounds. In particular, the synergistic dual catalytic system enabled the AAA reaction of challenging acyclic aliphatic ketones, such as b-ketocarbonyl compounds and 1,3-diketones.
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chiral Primary Amine palladium dual catalysis for asymmetric allylic alkylation of β ketocarbonyl compounds with allylic alcohols
Angewandte Chemie, 2015Co-Authors: Han Zhou, Long Zhang, Sanzhong LuoAbstract:An efficient dual catalytic system composed of a chiral Primary Amine and a palladium complex was developed to promote the direct asymmetric allylic alkylation (AAA) of β-ketocarbonyl compounds. In particular, the synergistic dual catalytic system enabled the AAA reaction of challenging acyclic aliphatic ketones, such as β-ketocarbonyl compounds and 1,3-diketones.
Sanzhong Luo - One of the best experts on this subject based on the ideXlab platform.
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reagent controlled enantioselectivity switch for the asymmetric fluorination of β ketocarbonyls by chiral Primary Amine catalysis
Chemical Science, 2017Co-Authors: Yangen You, Long Zhang, Sanzhong LuoAbstract:A reagent-controlled enantioselectivity switch was uncovered in the asymmetric α-fluorination of β-ketocarbonyls by a chiral Primary Amine catalyst. By a simple swap of fluorination reagents, both enantiomers of the quaternary fluorination adducts could be obtained with good yields and high enantioselectivity. Mechanistic studies disclosed dual H-bonding and electrostatic stereocontrolling modes for the catalysis.
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chiral Primary Amine palladium dual catalysis for asymmetric allylic alkylation of β ketocarbonyl compounds with allylic alcohols
Angewandte Chemie, 2015Co-Authors: Han Zhou, Long Zhang, Sanzhong LuoAbstract:An efficient dual catalytic system composed of a chiral Primary Amine and a palladium complex was developed to promote the direct asymmetric allylic alkylation (AAA) of β-ketocarbonyl compounds. In particular, the synergistic dual catalytic system enabled the AAA reaction of challenging acyclic aliphatic ketones, such as β-ketocarbonyl compounds and 1,3-diketones.
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catalytic asymmetric oxidative α c h n o ketalization of ketones by chiral Primary Amine
Organic Letters, 2015Co-Authors: Long Zhang, Sanzhong LuoAbstract:A highly enantioselective Primary Amine catalyzed α,α-bis-functionalization of β-ketocarbonyls and cyclohexanones is described. This transformation employs N-hydroxycarbamates as both nitrogen and oxygen sources under aerobic oxidative conditions to furnish chiral N,O-ketals with high yields and enantioselectivities.
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chiral Primary Amine catalyzed asymmetric tandem reduction michael addition protonation reaction between alkylidene meldrum s acid and α substituted vinyl ketones
Synthesis, 2015Co-Authors: Yinliang Guo, Long Zhang, Sanzhong LuoAbstract:One-pot three-component tandem reduction–Michael addition–protonation reactions of alkylidene Meldrum’s acids to α-substituted vinyl ketones have been developed by using a chiral Primary Amine as the organocatalyst, affording the products in excellent yields and with good enantioselectivity.
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chiral Primary Amine catalyzed asymmetric michael addition of malononitrile to α substituted vinyl ketone
Organic Letters, 2015Co-Authors: Long Zhang, Sanzhong LuoAbstract:The first efficient and highly enantioselective Michael addition–protonation reaction of malononitriles to α-substituted vinyl ketones has been developed by using a chiral Primary Amine as the organocatalyst. With a Hantzsch ester as the hydride source, an enantioselective tandem reduction, Michael addition–protonation reaction of benzylidenemalononitrile has also been achieved with good yields and high enantioselectivities.
Jin-pei Cheng - One of the best experts on this subject based on the ideXlab platform.
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asymmetric sulfa michael addition to α substituted vinyl ketones catalyzed by chiral Primary Amine
Organic Letters, 2014Co-Authors: Long Zhang, Sanzhong Luo, Jin-pei ChengAbstract:The first effective example of asymmetric conjugate addition–protonation reactions of thiols to α-substituted vinyl ketones by chiral Primary Amine catalysis is reported. A simple chiral Primary–tertiary diAmine catalyst derived from l-phenylalanine was found to promote the sulfa-Michael addition–protonation reactions with good to excellent enantioselectivity.
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chiral Primary Amine catalyzed conjugate addition to α substituted vinyl ketones aldehydes divergent stereocontrol modes on enAmine protonation
Chemistry: A European Journal, 2013Co-Authors: Long Zhang, Sanzhong Luo, Jin-pei ChengAbstract:Enantioselective protonation with a catalytic enAmine intermediate represents a challenging, yet fundamentally important process for the synthesis of α-chiral carbonyls. We describe herein chiral Primary-Amine-catalyzed conjugate additions of indoles to both α-substituted acroleins and vinyl ketones. These reactions feature enAmine protonation as the stereogenic step. A simple Primary–tertiary vicinal diAmine 1 with trifluoromethanesulfonic acid (TfOH) was found to enable both of the reactions of acroleins and vinyl ketones with good activity and high enantioselectivity. Detailed mechanistic studies reveal that these reactions are rate-limiting in iminium formation and they all involve a uniform H2O/acid-bridged proton transfer in the stereogenic steps but divergent stereocontrol modes for the protonation stereoselectivity. For the reactions of α-branched acroleins, facial selections on H2O-bridged protonation determine the enantioselectivity, which is enhanced by an OH⋅⋅⋅π interaction with indole as uncovered by DFT calculations. On the other hand, the stereoselectivity of the reactions with vinyl ketones is controlled according to the Curtin–Hammett principle in the CC bond-formation step, which precedes a highly stereospecific enAmine protonation.
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asymmetric synthesis of wieland miescher and hajos parrish ketones catalyzed by an amino acid derived chiral Primary Amine
Journal of Organic Chemistry, 2012Co-Authors: Pengxin Zhou, Long Zhang, Sanzhong Luo, Jin-pei ChengAbstract:This paper describes a simple chiral Primary Amine-catalyzed highly efficient and practical protocol for the synthesis of both Wieland–Miescher ketone and Hajos–Parrish ketone as well as their analogues. The reaction can be conducted in gram scale with 1% mol catalyst loading producing high enantioselectivity (up to 96% ee) and excellent yields (up to 98%). This procedure represents one of the most efficient methods for the synthesis of these versatile chiral building blocks.
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Asymmetric supramolecular Primary Amine catalysis in aqueous buffer: connections of selective recognition and asymmetric catalysis.
Journal of the American Chemical Society, 2010Co-Authors: Junfeng Xiang, Jie Pan, Sanzhong Luo, Jin-pei ChengAbstract:A new approach of asymmetric supramolecular catalysis has been developed by combining the supramolecular recognition of β-cyclodextrin (β-CD) and the superior property of a chiral Primary Amine catalyst. The resulted β-CD enAmine catalysts could effectively promote asymmetric direct aldol reactions with excellent enantioselectivity in an aqueous buffer solution (pH = 4.80). The identified optimal catalyst CD-1 shows interesting characteristics of supramolecular catalysis with selective recognition of aldol acceptors and donors. A detailed mechanistic investigation on such supramolecular catalysis was conducted with the aid of NMR, fluorescence, circular dichroism, and ESI-MS analysis. It is revealed that the reaction is initialized first by binding substrates into the cyclodextrin cavity via a synergistic action of hydrophobic interaction and noncovalent interaction with the CD-1 side chain. A rate-limiting enAmine forming step is then involved which is followed by the product-generating C−C bond formatio...
Yi Zhang - One of the best experts on this subject based on the ideXlab platform.
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measurement and modeling for vanadium extraction from the navo3 h2so4 h2o system by Primary Amine n1923
The Journal of Chemical Thermodynamics, 2015Co-Authors: Pengge Ning, Yi ZhangAbstract:Abstract In this work, the solvent extraction of vanadium by using the Primary Amine N1923 as extractant was studied. Within different vanadium concentration ranges, the extraction reactions were determined using the slope method at T = 298.15 K based on the vanadium phase diagram. The slopes (the stoichiometric ratio) were determined as 5/3, 1 and 11/3 for ( RNH 2 ) 5 / 3 H 3 VO 4 , ( RNH 2 ) H 3 V 3 O 9 and ( RNH 2 ) 11 / 3 H 6 V 10 O 28 , respectively. The thermodynamic model was established through regression of the experimental results with the Pitzer equation for both aqueous and organic phases by the General Algebraic Modelling System (GAMS). Three different sets of parameters and chemical equilibrium constants K were determined, which corresponded to the three extraction reactions. The orders of the lnK values are V 10 > V 3 > V 1 (organic V species), and the distribution coefficients ( D V ) are D V 1 > D V 3 > D V 10 . The new model was applied to predict the regularities of extraction yield along with different initial conditions, and the results agree well with the experimental values.
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selective extraction and deep separation of v v and cr vi in the leaching solution of chromium bearing vanadium slag with Primary Amine lk n21
Separation and Purification Technology, 2014Co-Authors: Pengge Ning, Xiao Lin, Hongbin Cao, Yi ZhangAbstract:In this report the extraction of V(V) and Cr(VI) from a synthetic feed solution and real leaching solution of the chromium-bearing vanadium slag (V-Cr slag) using Primary Amine LK-N21 was studied. Detailed fundamental research work was conducted to investigate the Primary Amine extracting V(V) and Cr(VI). The mechanism and the difference between the two metals of extraction were studied and the experimental results were compared with previously published data. The optimum technological parameters for the separation of two metals were determined including: pH value in feed solution, phase ratio, mixing time, as well as others. The results showed that Primary Amine LK-N21 can extract V(V) selectively by hydrogen bonding association. Cr(VI) competed V(V) to combine with the Primary Amine, and the concentration of Cr(VI) decided the percentage extraction of V(V) and Cr(VI). Primary Amine LK-N21 extracted more than 90% of V(V) which resulted in over 90% of Cr(VI) left in the leaching solution of the V-Cr slag in the optimal conditions. Based on the results of experiments, V(V) and Cr(VI) can be separated with a high degree of selectivity. (C) 2014 Published by Elsevier B.V.
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selective extraction and deep removal of tungsten from sodium molybdate solution by Primary Amine n1923
Separation and Purification Technology, 2009Co-Authors: Pengge Ning, Yi ZhangAbstract:Selectively extracting tungsten to purify sodium molybdate solution was studied using Primary Amine N1923, including various conditions, such as equilibrium pH values, concentrations of extractant in organic phase and metals in feed solution, contact time of extraction and stripping, types of acidic solutions added, temperature of extraction and the dosage of stripping agent. Graphical method using McCabe-Thiele diagram and counter-current extraction simulation (CCES) were used to determine the required stages of deep removal of tungsten. The results show that appropriate concentrations of tungsten and molybdenum in feed solution have great influence on the difficult degree of the separation between the two metals. Organic phase including 0.051 M of N1923 modified by LK-N21X diluted in kerosene can extract 92.7% of tungsten in sulfuric acid solution at equilibrium pH value of 7.07 for 10 min in one-stage extraction at 15.5 degrees C, and the separation factor reaches 329 under those optimum conditions. A two-stage CCES removes 99.83% of tungsten and obtains the purified sodium molybdate solution where W/Mo (mass ratio) reaches 2.9 x 10(-5). Stripping can be accomplished by NaOH solution completely and quickly. Furthermore, the extraction and stripping reactions of tungsten and molybdenum in equilibrium were proposed. (C) 2009 Elsevier B.V. All rights reserved.
Pengge Ning - One of the best experts on this subject based on the ideXlab platform.
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measurement and modeling for vanadium extraction from the navo3 h2so4 h2o system by Primary Amine n1923
The Journal of Chemical Thermodynamics, 2015Co-Authors: Pengge Ning, Yi ZhangAbstract:Abstract In this work, the solvent extraction of vanadium by using the Primary Amine N1923 as extractant was studied. Within different vanadium concentration ranges, the extraction reactions were determined using the slope method at T = 298.15 K based on the vanadium phase diagram. The slopes (the stoichiometric ratio) were determined as 5/3, 1 and 11/3 for ( RNH 2 ) 5 / 3 H 3 VO 4 , ( RNH 2 ) H 3 V 3 O 9 and ( RNH 2 ) 11 / 3 H 6 V 10 O 28 , respectively. The thermodynamic model was established through regression of the experimental results with the Pitzer equation for both aqueous and organic phases by the General Algebraic Modelling System (GAMS). Three different sets of parameters and chemical equilibrium constants K were determined, which corresponded to the three extraction reactions. The orders of the lnK values are V 10 > V 3 > V 1 (organic V species), and the distribution coefficients ( D V ) are D V 1 > D V 3 > D V 10 . The new model was applied to predict the regularities of extraction yield along with different initial conditions, and the results agree well with the experimental values.
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selective extraction and deep separation of v v and cr vi in the leaching solution of chromium bearing vanadium slag with Primary Amine lk n21
Separation and Purification Technology, 2014Co-Authors: Pengge Ning, Xiao Lin, Hongbin Cao, Yi ZhangAbstract:In this report the extraction of V(V) and Cr(VI) from a synthetic feed solution and real leaching solution of the chromium-bearing vanadium slag (V-Cr slag) using Primary Amine LK-N21 was studied. Detailed fundamental research work was conducted to investigate the Primary Amine extracting V(V) and Cr(VI). The mechanism and the difference between the two metals of extraction were studied and the experimental results were compared with previously published data. The optimum technological parameters for the separation of two metals were determined including: pH value in feed solution, phase ratio, mixing time, as well as others. The results showed that Primary Amine LK-N21 can extract V(V) selectively by hydrogen bonding association. Cr(VI) competed V(V) to combine with the Primary Amine, and the concentration of Cr(VI) decided the percentage extraction of V(V) and Cr(VI). Primary Amine LK-N21 extracted more than 90% of V(V) which resulted in over 90% of Cr(VI) left in the leaching solution of the V-Cr slag in the optimal conditions. Based on the results of experiments, V(V) and Cr(VI) can be separated with a high degree of selectivity. (C) 2014 Published by Elsevier B.V.
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selective extraction and deep removal of tungsten from sodium molybdate solution by Primary Amine n1923
Separation and Purification Technology, 2009Co-Authors: Pengge Ning, Yi ZhangAbstract:Selectively extracting tungsten to purify sodium molybdate solution was studied using Primary Amine N1923, including various conditions, such as equilibrium pH values, concentrations of extractant in organic phase and metals in feed solution, contact time of extraction and stripping, types of acidic solutions added, temperature of extraction and the dosage of stripping agent. Graphical method using McCabe-Thiele diagram and counter-current extraction simulation (CCES) were used to determine the required stages of deep removal of tungsten. The results show that appropriate concentrations of tungsten and molybdenum in feed solution have great influence on the difficult degree of the separation between the two metals. Organic phase including 0.051 M of N1923 modified by LK-N21X diluted in kerosene can extract 92.7% of tungsten in sulfuric acid solution at equilibrium pH value of 7.07 for 10 min in one-stage extraction at 15.5 degrees C, and the separation factor reaches 329 under those optimum conditions. A two-stage CCES removes 99.83% of tungsten and obtains the purified sodium molybdate solution where W/Mo (mass ratio) reaches 2.9 x 10(-5). Stripping can be accomplished by NaOH solution completely and quickly. Furthermore, the extraction and stripping reactions of tungsten and molybdenum in equilibrium were proposed. (C) 2009 Elsevier B.V. All rights reserved.
