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 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 new chiral ligand N p toluenesulfonyl 2,2′ dimethoxy 6,6′ diaminobiphenyl (Ts DMBDPPA) was prepared from 2,2′ dimethoxy 6,6′ diaminobiphenyl via N tosylation. Its Ru(II) complex was effec...A new chiral ligand N p toluenesulfonyl 2,2′ dimethoxy 6,6′ diaminobiphenyl (Ts DMBDPPA) was prepared from 2,2′ dimethoxy 6,6′ diaminobiphenyl via N tosylation. Its Ru(II) complex was effective catalysts for catalytic asymmetric transfer hydrogenation of aromatic ketones (with ee 's up to 69.3%).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
Chiral ligand (R)-N, N'-Bis(2-hydroxy-3,5-di- tert-butyl-aryl-methyl)-1, 1'-binaphthalene-2,2'-diamine derived from the reduction of Schiff base (R)-2,2'-bis (3,5-di-tert-butyl-2-hy-droxybenzylideneami...Chiral ligand (R)-N, N'-Bis(2-hydroxy-3,5-di- tert-butyl-aryl-methyl)-1, 1'-binaphthalene-2,2'-diamine derived from the reduction of Schiff base (R)-2,2'-bis (3,5-di-tert-butyl-2-hy-droxybenzylideneamino)-1, 1'-binaphthyl with LiAIH(4) is fairly effective in the asymmetric addition reaction of diethylzinc to aldehydes by which good yields (46%-94%) of the corresponding sec-alcohols can be obtained in moderate ee (51%-79%) with R configuration for a variety of aldehydes.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
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
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
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
In the process of resolution of DL-amino acids by ligand exchange chromatography, the matrix of the packing has great effect on the resolution efficiency. Lefebvre et al.reported that chiral packing (Ⅰ) with hydrophi...In the process of resolution of DL-amino acids by ligand exchange chromatography, the matrix of the packing has great effect on the resolution efficiency. Lefebvre et al.reported that chiral packing (Ⅰ) with hydrophilic polyacrylamide matrix has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.
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
An enantiopure helical coordination polymer AgPF6·（R）-3 as crystalline solid was synthesized by the self-assembly of chiral binaphthyl-based ligand（R）-6,6＇-di[6-（2,2＇-bipyridyl）]-2,2＇-diethoxyl-1,1＇-bin...An enantiopure helical coordination polymer AgPF6·（R）-3 as crystalline solid was synthesized by the self-assembly of chiral binaphthyl-based ligand（R）-6,6＇-di[6-（2,2＇-bipyridyl）]-2,2＇-diethoxyl-1,1＇-binaphthalene [（R）-3] and Ag＋ ion.The single crystal structural analysis indicates that this polymer exhibits an infinite cylindric single-stranded M-helical structure with local Λ configuration at each tetrahedral metal center.However,the extended structure is dissociated into some oligomeric fragments in solution.The 1H NMR spectra of complex AgPF6·（R）-3 show that the ligand possesses a good C2 symmetry,and the chemical shifts of the protons depend on the concentration and temperature.In addition,there are rapid dynamic exchanges among some oligonuclear fragments in the solution of AgPF6·（R）-3.展开更多
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 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 new chiral ligand N p toluenesulfonyl 2,2′ dimethoxy 6,6′ diaminobiphenyl (Ts DMBDPPA) was prepared from 2,2′ dimethoxy 6,6′ diaminobiphenyl via N tosylation. Its Ru(II) complex was effective catalysts for catalytic asymmetric transfer hydrogenation of aromatic ketones (with ee 's up to 69.3%).
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.
基金theMajorStateBasicResearchDevelopmentProgram (No .G2 0 0 0 0 480 0 7)andtheNationalNaturalScienceFoundationofChina (No .2 0 0 2 5 2 0 6 )
文摘Chiral ligand (R)-N, N'-Bis(2-hydroxy-3,5-di- tert-butyl-aryl-methyl)-1, 1'-binaphthalene-2,2'-diamine derived from the reduction of Schiff base (R)-2,2'-bis (3,5-di-tert-butyl-2-hy-droxybenzylideneamino)-1, 1'-binaphthyl with LiAIH(4) is fairly effective in the asymmetric addition reaction of diethylzinc to aldehydes by which good yields (46%-94%) of the corresponding sec-alcohols can be obtained in moderate ee (51%-79%) with R configuration for a variety of aldehydes.
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.
文摘In the process of resolution of DL-amino acids by ligand exchange chromatography, the matrix of the packing has great effect on the resolution efficiency. Lefebvre et al.reported that chiral packing (Ⅰ) with hydrophilic polyacrylamide matrix has
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Supported by the National Natural Science Foundation of China(No.20502024)
文摘An enantiopure helical coordination polymer AgPF6·（R）-3 as crystalline solid was synthesized by the self-assembly of chiral binaphthyl-based ligand（R）-6,6＇-di[6-（2,2＇-bipyridyl）]-2,2＇-diethoxyl-1,1＇-binaphthalene [（R）-3] and Ag＋ ion.The single crystal structural analysis indicates that this polymer exhibits an infinite cylindric single-stranded M-helical structure with local Λ configuration at each tetrahedral metal center.However,the extended structure is dissociated into some oligomeric fragments in solution.The 1H NMR spectra of complex AgPF6·（R）-3 show that the ligand possesses a good C2 symmetry,and the chemical shifts of the protons depend on the concentration and temperature.In addition,there are rapid dynamic exchanges among some oligonuclear fragments in the solution of AgPF6·（R）-3.
