Several new chiral organogallium and indium complexes with chiral Salen (1 and 2) as anxciliary ligands have been synthesized and characterized by elemental analysis, IR, 1H NMR and Mass spectroscopy. For the gallium...Several new chiral organogallium and indium complexes with chiral Salen (1 and 2) as anxciliary ligands have been synthesized and characterized by elemental analysis, IR, 1H NMR and Mass spectroscopy. For the gallium, mono and bimetallic complexes were obtained, whereas ring closure complexes of indium were obtained.展开更多
Three chiral stationary phases（CSPl, CSP2 and CSP3） for ligand-exchange chromatography were prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol groups on the surfa...Three chiral stationary phases（CSPl, CSP2 and CSP3） for ligand-exchange chromatography were prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol groups on the surface of silica gel, and then modifying the surface of silica gel with allyl glycidyl ether and alkenes through the hydrosilation reaction, and lastly introducing L-proline as a chiral selector. The enantiomer resolutions of 14 amino acids and 2 hydroxyl acids were completed on the CSPs by using an aqueous solution of Cu（Ac）2 as mobile phase at a flow rate of 1.0 mL/min and column temperature of 40 ℃ with detection at UV 254 nm. In terms of enantioseleetivity a, column efficiency and resolution Rs, the chromatographic behaviors of the analytes on the CSPs were discussed via comparing them to those on the CSP4 prepared via the reference method. The results show that enantioselectivity a, column efficiency and resolution Rs of the analytes on the CSPs could be improved by using the above modifying method.展开更多
Click chemistry was applied to immobilize L-proline derivative onto azide-modified silica gel to give a novel chiral stationary phase （denoted as click-CSP） for ligand exchange chromatography. The developed protocol...Click chemistry was applied to immobilize L-proline derivative onto azide-modified silica gel to give a novel chiral stationary phase （denoted as click-CSP） for ligand exchange chromatography. The developed protocol combines the benefits of operational simplicity, exceptionally mild conditions and high surface loadings. The enantioselectivity α of some DL-arnino acids on the click- CSP were found to be in the range from 1.13 to 3.46. The chromatographic resolutions of some DL-amino acids and the stability study firmly illustrate the potential of click chemistry for preparation chiral stationary phase for ligand exchange chromatography.展开更多
Chiral ionic liquids (CILs) containing imidazolium cations and L-Proline (L-Pro) anions were applied as chiral selector to separate tryptophan (Trp) enantiomers on a C18 column by ligand exchange chromatography. Sever...Chiral ionic liquids (CILs) containing imidazolium cations and L-Proline (L-Pro) anions were applied as chiral selector to separate tryptophan (Trp) enantiomers on a C18 column by ligand exchange chromatography. Several factors influencing Trp enantiomers separation, such as alkyl chain length of CILs, concentrations of Cu2+ and CILs, pH of the mobile phase, flow rate, organic solvent and temperature, were studied. Under the optimal conditions, the Trp enantiomers could be successfully separated within 21 min with the resolution of 2.30. At the same time, some thermodynamical parameters were obtained. The experimental results show that the enthalpy values of the Trp enantiomers are negative, indicating that the separation process is exothermic. And the enthalpy values of D-Trp are larger than those of L-Trp, which indicates that L-Trp could form more stable ternary complexes with tryptophan enantiomers.展开更多
Three new hybrid organic/inorganic polymeric ligand-exchange chiral stationary phases were developed by radical chain transfer reaction and surface grafting on silica gel, and successfully used for the enantioseparati...Three new hybrid organic/inorganic polymeric ligand-exchange chiral stationary phases were developed by radical chain transfer reaction and surface grafting on silica gel, and successfully used for the enantioseparations of DL-amino acids and DL-hydroxyl adds. The resolutions were achieved by using water containing 2.0 × 10^-4 mol/L of CuAc2 as a mobile phase, column temperature of 40 ℃, flow rate of 1.0 mL/min and detection at UV 254 nm. The elution order of D-isomer before L-isomer was observed for all DL-amino acids resolved except DL-Pro.展开更多
Based on the chiral ligand exchange, the distribution behavior of mandelic acid enantiomers, and the partition of Cu2+ at different pH values were studied in a water/alcohol two-phase system containing Cu2+ and N-n-（...Based on the chiral ligand exchange, the distribution behavior of mandelic acid enantiomers, and the partition of Cu2+ at different pH values were studied in a water/alcohol two-phase system containing Cu2+ and N-n-（dodecyl-L-proline（A）.） The influences of the solvent sort, the pH value, the concentrations of Cu2+ and chiral ligand on the partition coefficient（K） and separation factor（α） were discussed. The experimental results show that the A formed has more stable ternary complex with D-mandelic acid enantiomer than with L-mandelic acid enantiomer. There is an important influence of the pH value on K and α. When the pH values are less than 3.5, the formation of binary complexes is thermodynamically unfavourable. K and α become maximum when pH values are above 3.5 and the molar ratio of the chiral ligand to Cu2+ is 2∶1.展开更多
A series of novel enantiomerically pure diols were synthesized from D-erythorbic acid in three steps, and the absolute configuration of one of them 4a has been confirmed by X-ray analysis.
Several kinds of chiral heterocyclic ligands without hydroxyl group have been synthesized and used as catalysts for the asymmetric addition of diethylzinc to benzaldehyde. These ligands promoted the formation of (S)-1...Several kinds of chiral heterocyclic ligands without hydroxyl group have been synthesized and used as catalysts for the asymmetric addition of diethylzinc to benzaldehyde. These ligands promoted the formation of (S)-1-phenylpropanols in good yields and medium to good enantioselectivities (50 similar to 86 % ee.).展开更多
Methyl methacrylate was anionically polymerized in the presence of chiral ligands, e. g. (+)-DDB and (-)-Sp. The polymers thus formed were optically inactive due to the instability of the helical chain for the less bu...Methyl methacrylate was anionically polymerized in the presence of chiral ligands, e. g. (+)-DDB and (-)-Sp. The polymers thus formed were optically inactive due to the instability of the helical chain for the less bulky ester group. Isotactic poly(methyl methacrylate) was given when (+)-DDB was used, whereas, a syndiotactic polymer was formed in the presence of (-)-Sp. Accordingly, two different propagation mechanisms were postulated.展开更多
The syntheses of a library of new chiral aminophenolate bidentate O,N-type ligands HOC<sub>6</sub>H<sub>4</sub>(2-R- 4-R′)CH<sub>2</sub>N(Me)CH(Me)C<sub>6</sub>H<sub...The syntheses of a library of new chiral aminophenolate bidentate O,N-type ligands HOC<sub>6</sub>H<sub>4</sub>(2-R- 4-R′)CH<sub>2</sub>N(Me)CH(Me)C<sub>6</sub>H<sub>5</sub> [R = R′ = Bu<sup>t</sup>, 1;R = R′ = Pent, 2;R = Bu<sup>t</sup>, R′ = Me, 3;R = Me, R′ = Bu<sup>t</sup>, 4;R = R′ = Me, 5] and tridentate O,N,O-type ligands HOC<sub>6</sub>H<sub>4</sub>(2,4-Bu<sup>t</sup>)CH = NCH(R′′)C<sub>6</sub>H<sub>5</sub> [R′′ = Me, 6;R′′ = CH<sub>2</sub>OMe, 7] are reported. These ligands were characterized by elemental analysis, nuclear magnetic resonance spectroscopy (<sup>1</sup>H &<sup> 13</sup>C), and single crystal X-ray diffraction. These ligands serve as chiral auxiliaries for inorganic chemists to design chiral metal-based complexes for asymmetric catalysis and stereoselective polymerization reactions. Three new heteroleptic zinc complexes based on these ligands have been synthesized in moderate yields via a ligand-exchange transamination reaction between homoleptic [Zn(N(SiMe<sub>3</sub>)<sub>2</sub>)<sub>2</sub>] and one equivalent of corresponding ligands to afford [L<sup>3</sup>ZnN- (SiMe<sub>3</sub>)<sub>2</sub>] (3a), [L<sup>4</sup>ZnN(SiMe<sub>3</sub>)<sub>2</sub>] (4a), and [L<sup>7</sup>ZnN(SiMe<sub>3</sub>)<sub>2</sub>] (7a). Solvent-free polymerization of raclactide at 130°C using these zinc compounds yielded atactic polylactides with Mw 10,000 g/mol and narrow polydispersity of 1.3.展开更多
The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.
A novel chiral stationary phase （CSP1） for ligand-exchange chromatography （CLEC） was prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol group on the surface of ...A novel chiral stationary phase （CSP1） for ligand-exchange chromatography （CLEC） was prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol group on the surface of silica gel, and then introducing L-Pro as a chiral selector and hydrophobic octyl group to the silica gel surface simultaneously. The enantioseparations of 14 DL-amino acids on CSP1 were achieved with the enantioselectivity α ranging from 1.09 to 2.44 and the resolution Rs being between 0.8 and 6.3. The chromatographic performances of CSP1 with the bonded phase （CSP2） prepared using reference method were compared. The results showed that the column efficiency and resolution Rs of chiral stationary phase could be improved by using the above modifying method.展开更多
The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framewor...The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framework and has been utilized as an important toolbox due to their structural stability.Herein,we design and synthesize[2.2]paracyclophane-derived oxazole-pyrimidine ligands(abberviated as PYMCOX).These N,N-ligands with stable properties,rigid structure and large steric hindrance performed successfully in nickel-catalyzed asymmetric 1,2-reduction ofα,β-unsaturated ketones,affording the chiral allylic alcohols with up to 99%yield and 99%ee.Meanwhile,this reduction reaction could be conducted on gram-scale without loss of activity and enantioselectivity,and the chiral ligand could be conveniently recovered with high yield.展开更多
The efficient catalytic systems generated in situ from RuCl2（PPh3）3 and chiral ligands N,N-bis[2-（di-o-tolylphosphino）-benzyl]cyclohexane-1,2-diamine（2） were employed for asymmetric transfer hydrogenation of aro...The efficient catalytic systems generated in situ from RuCl2（PPh3）3 and chiral ligands N,N-bis[2-（di-o-tolylphosphino）-benzyl]cyclohexane-1,2-diamine（2） were employed for asymmetric transfer hydrogenation of aromatic ketones, giving the corresponding optically active alcohols with high activities（up to 99% conversion） and excellent enantioselectivities（up to 96% e.e.） under mild conditions. The chiral ruthenium（Ⅱ） complex （R,R）-3 has been prepared and characterized by NMR and X-ray crystallography.展开更多
The enantioseparation of dencichine and its D-isomer was achieved on a novel chiral stationary phase via coating N-（2-hydroxyl-3-octoxyl） propyl-S-benzyl-（L）-cysteine on YWG-C18 phase by ligand exchange chromatogr...The enantioseparation of dencichine and its D-isomer was achieved on a novel chiral stationary phase via coating N-（2-hydroxyl-3-octoxyl） propyl-S-benzyl-（L）-cysteine on YWG-C18 phase by ligand exchange chromatography.展开更多
基金the National Natural Science Foundation of China (20102002) Science Foundation of Jiangsu Province (BK2001030) and the 863 High Technology Program for their financial support. The research funds for Y. Pan from Qin-Lan Program of Jiangsu Province and
文摘Several new chiral organogallium and indium complexes with chiral Salen (1 and 2) as anxciliary ligands have been synthesized and characterized by elemental analysis, IR, 1H NMR and Mass spectroscopy. For the gallium, mono and bimetallic complexes were obtained, whereas ring closure complexes of indium were obtained.
文摘Three chiral stationary phases（CSPl, CSP2 and CSP3） for ligand-exchange chromatography were prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol groups on the surface of silica gel, and then modifying the surface of silica gel with allyl glycidyl ether and alkenes through the hydrosilation reaction, and lastly introducing L-proline as a chiral selector. The enantiomer resolutions of 14 amino acids and 2 hydroxyl acids were completed on the CSPs by using an aqueous solution of Cu（Ac）2 as mobile phase at a flow rate of 1.0 mL/min and column temperature of 40 ℃ with detection at UV 254 nm. In terms of enantioseleetivity a, column efficiency and resolution Rs, the chromatographic behaviors of the analytes on the CSPs were discussed via comparing them to those on the CSP4 prepared via the reference method. The results show that enantioselectivity a, column efficiency and resolution Rs of the analytes on the CSPs could be improved by using the above modifying method.
文摘Click chemistry was applied to immobilize L-proline derivative onto azide-modified silica gel to give a novel chiral stationary phase （denoted as click-CSP） for ligand exchange chromatography. The developed protocol combines the benefits of operational simplicity, exceptionally mild conditions and high surface loadings. The enantioselectivity α of some DL-arnino acids on the click- CSP were found to be in the range from 1.13 to 3.46. The chromatographic resolutions of some DL-amino acids and the stability study firmly illustrate the potential of click chemistry for preparation chiral stationary phase for ligand exchange chromatography.
基金Project(21176262) supported by the National Natural Science Foundation of ChinaProject(2010WK3029) supported by Science and Technology Program of Hunan Province,China
文摘Chiral ionic liquids (CILs) containing imidazolium cations and L-Proline (L-Pro) anions were applied as chiral selector to separate tryptophan (Trp) enantiomers on a C18 column by ligand exchange chromatography. Several factors influencing Trp enantiomers separation, such as alkyl chain length of CILs, concentrations of Cu2+ and CILs, pH of the mobile phase, flow rate, organic solvent and temperature, were studied. Under the optimal conditions, the Trp enantiomers could be successfully separated within 21 min with the resolution of 2.30. At the same time, some thermodynamical parameters were obtained. The experimental results show that the enthalpy values of the Trp enantiomers are negative, indicating that the separation process is exothermic. And the enthalpy values of D-Trp are larger than those of L-Trp, which indicates that L-Trp could form more stable ternary complexes with tryptophan enantiomers.
文摘Three new hybrid organic/inorganic polymeric ligand-exchange chiral stationary phases were developed by radical chain transfer reaction and surface grafting on silica gel, and successfully used for the enantioseparations of DL-amino acids and DL-hydroxyl adds. The resolutions were achieved by using water containing 2.0 × 10^-4 mol/L of CuAc2 as a mobile phase, column temperature of 40 ℃, flow rate of 1.0 mL/min and detection at UV 254 nm. The elution order of D-isomer before L-isomer was observed for all DL-amino acids resolved except DL-Pro.
基金Project(20376085) supported by the National Natural Science Foundation of China
文摘Based on the chiral ligand exchange, the distribution behavior of mandelic acid enantiomers, and the partition of Cu2+ at different pH values were studied in a water/alcohol two-phase system containing Cu2+ and N-n-（dodecyl-L-proline（A）.） The influences of the solvent sort, the pH value, the concentrations of Cu2+ and chiral ligand on the partition coefficient（K） and separation factor（α） were discussed. The experimental results show that the A formed has more stable ternary complex with D-mandelic acid enantiomer than with L-mandelic acid enantiomer. There is an important influence of the pH value on K and α. When the pH values are less than 3.5, the formation of binary complexes is thermodynamically unfavourable. K and α become maximum when pH values are above 3.5 and the molar ratio of the chiral ligand to Cu2+ is 2∶1.
基金the National Natural Science Foundation of China for the project support (No. 29972021 )
文摘A series of novel enantiomerically pure diols were synthesized from D-erythorbic acid in three steps, and the absolute configuration of one of them 4a has been confirmed by X-ray analysis.
文摘Several kinds of chiral heterocyclic ligands without hydroxyl group have been synthesized and used as catalysts for the asymmetric addition of diethylzinc to benzaldehyde. These ligands promoted the formation of (S)-1-phenylpropanols in good yields and medium to good enantioselectivities (50 similar to 86 % ee.).
文摘Methyl methacrylate was anionically polymerized in the presence of chiral ligands, e. g. (+)-DDB and (-)-Sp. The polymers thus formed were optically inactive due to the instability of the helical chain for the less bulky ester group. Isotactic poly(methyl methacrylate) was given when (+)-DDB was used, whereas, a syndiotactic polymer was formed in the presence of (-)-Sp. Accordingly, two different propagation mechanisms were postulated.
文摘The syntheses of a library of new chiral aminophenolate bidentate O,N-type ligands HOC<sub>6</sub>H<sub>4</sub>(2-R- 4-R′)CH<sub>2</sub>N(Me)CH(Me)C<sub>6</sub>H<sub>5</sub> [R = R′ = Bu<sup>t</sup>, 1;R = R′ = Pent, 2;R = Bu<sup>t</sup>, R′ = Me, 3;R = Me, R′ = Bu<sup>t</sup>, 4;R = R′ = Me, 5] and tridentate O,N,O-type ligands HOC<sub>6</sub>H<sub>4</sub>(2,4-Bu<sup>t</sup>)CH = NCH(R′′)C<sub>6</sub>H<sub>5</sub> [R′′ = Me, 6;R′′ = CH<sub>2</sub>OMe, 7] are reported. These ligands were characterized by elemental analysis, nuclear magnetic resonance spectroscopy (<sup>1</sup>H &<sup> 13</sup>C), and single crystal X-ray diffraction. These ligands serve as chiral auxiliaries for inorganic chemists to design chiral metal-based complexes for asymmetric catalysis and stereoselective polymerization reactions. Three new heteroleptic zinc complexes based on these ligands have been synthesized in moderate yields via a ligand-exchange transamination reaction between homoleptic [Zn(N(SiMe<sub>3</sub>)<sub>2</sub>)<sub>2</sub>] and one equivalent of corresponding ligands to afford [L<sup>3</sup>ZnN- (SiMe<sub>3</sub>)<sub>2</sub>] (3a), [L<sup>4</sup>ZnN(SiMe<sub>3</sub>)<sub>2</sub>] (4a), and [L<sup>7</sup>ZnN(SiMe<sub>3</sub>)<sub>2</sub>] (7a). Solvent-free polymerization of raclactide at 130°C using these zinc compounds yielded atactic polylactides with Mw 10,000 g/mol and narrow polydispersity of 1.3.
文摘The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.
文摘A novel chiral stationary phase （CSP1） for ligand-exchange chromatography （CLEC） was prepared by firstly using dimethylchlorosilane as an endcapping reagent for decreasing residual silanol group on the surface of silica gel, and then introducing L-Pro as a chiral selector and hydrophobic octyl group to the silica gel surface simultaneously. The enantioseparations of 14 DL-amino acids on CSP1 were achieved with the enantioselectivity α ranging from 1.09 to 2.44 and the resolution Rs being between 0.8 and 6.3. The chromatographic performances of CSP1 with the bonded phase （CSP2） prepared using reference method were compared. The results showed that the column efficiency and resolution Rs of chiral stationary phase could be improved by using the above modifying method.
基金Financial support from National Natural Science Foundation of China (22171260)K.C.Wong Education Foundation of CAS (GJTD-2020-08)is acknowledged.
文摘The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framework and has been utilized as an important toolbox due to their structural stability.Herein,we design and synthesize[2.2]paracyclophane-derived oxazole-pyrimidine ligands(abberviated as PYMCOX).These N,N-ligands with stable properties,rigid structure and large steric hindrance performed successfully in nickel-catalyzed asymmetric 1,2-reduction ofα,β-unsaturated ketones,affording the chiral allylic alcohols with up to 99%yield and 99%ee.Meanwhile,this reduction reaction could be conducted on gram-scale without loss of activity and enantioselectivity,and the chiral ligand could be conveniently recovered with high yield.
基金Supported by the National Natural Science Foundation of China(Nos.2042300220703034)+1 种基金the Natural Science Foundation of Fujian Province of China(No.2008J0235)the Natural Science Foundation of Guangxi Province of China(No. 0991016)
文摘The efficient catalytic systems generated in situ from RuCl2（PPh3）3 and chiral ligands N,N-bis[2-（di-o-tolylphosphino）-benzyl]cyclohexane-1,2-diamine（2） were employed for asymmetric transfer hydrogenation of aromatic ketones, giving the corresponding optically active alcohols with high activities（up to 99% conversion） and excellent enantioselectivities（up to 96% e.e.） under mild conditions. The chiral ruthenium（Ⅱ） complex （R,R）-3 has been prepared and characterized by NMR and X-ray crystallography.
文摘The enantioseparation of dencichine and its D-isomer was achieved on a novel chiral stationary phase via coating N-（2-hydroxyl-3-octoxyl） propyl-S-benzyl-（L）-cysteine on YWG-C18 phase by ligand exchange chromatography.
