A series of C_2-symmetrical chiral 2,5-bis(4'-alkyloxazolin-2-yl) thiophenes(thiobox) have been synthesized from thiophene-2,5-dicarboxylic acid by sequential amidation with achiral ethanolamine, conversion of hyd...A series of C_2-symmetrical chiral 2,5-bis(4'-alkyloxazolin-2-yl) thiophenes(thiobox) have been synthesized from thiophene-2,5-dicarboxylic acid by sequential amidation with achiral ethanolamine, conversion of hydroxyl to chloro group, and base-promoted oxazoline ringformation. As demonstrated by (-)-2,5-bis[4'-(S)-isopropyloxazolin-2'-yl] thiophene, these thioboxsystems exhibited remarkable chirality recognition of 1,1'-bi-2-naphthol giving rise to pronouncedshifts in the ~1H NMR signals of the latter axial chiral compound at the positions of C-3, C-4, C-5,and C-8.展开更多
The lanthanide chelates of(l)-2,2-dimethyl-6-trifluoromethyl-7-oxa-6,8,8,9,9,10, 10,10-octafluoro-3,5-decanedione,Ln[(l)-CF_3CF_2CF_2OCF(CF_3)COCHCOC(CH_3)_3]_3(l-3a,Ln=Eu; 3b, Ln=Pr), are useful as ~1H NMR shift reag...The lanthanide chelates of(l)-2,2-dimethyl-6-trifluoromethyl-7-oxa-6,8,8,9,9,10, 10,10-octafluoro-3,5-decanedione,Ln[(l)-CF_3CF_2CF_2OCF(CF_3)COCHCOC(CH_3)_3]_3(l-3a,Ln=Eu; 3b, Ln=Pr), are useful as ~1H NMR shift reagents for direct determination of enantiomeric composition of enantiomorphous alcohols. ketones and amines. With these substrates. l-3a induces shift difference similar to that induced by Eu(facam)_3 and Eu(hfbc)_3. However, due to the higher solubility of the chelates l-3a and l-3b in nonpolar organic solvent such as CHCl_3, CCl_4 and only one ~1H signal from l-3a and l-3b is observed. their application as the new chiral shift reagents seems promising. The spectral nonequivalence is also observed for dimethylsulfoxide in the presence of l-3a.展开更多
目的研究手性分子与核磁共振(NMR)谱图之间的关系,为手性化合物研究提供参考。方法通过举例分析,阐述手性分子与NMR谱图之间的关系。如毗邻一个手性中心的亚甲基中的2个质子化学位移并非等价,—CH_2—基团实际上是—CH_aH_b—结构。此...目的研究手性分子与核磁共振(NMR)谱图之间的关系,为手性化合物研究提供参考。方法通过举例分析,阐述手性分子与NMR谱图之间的关系。如毗邻一个手性中心的亚甲基中的2个质子化学位移并非等价,—CH_2—基团实际上是—CH_aH_b—结构。此方法可以用来确定ee%(对映体过量)值。结果给出了应用手性衍生试剂、手性溶剂化试剂和手性位移试剂来确定ee%值的方法;此外,对手性螺环化合物的~1 H NMR谱图也进行了讨论。结论对于手性分子与NMR谱图之间关系的研究,可为通过NMR谱图表征手性分子提供参考。展开更多
用1 H NMR和13 C NMR研究了水溶性镧系位移试剂Sm-pdta对反式-4-羟基脯氨酸的手性识别.反式-4-羟基脯氨酸与Sm-pdta形成络合物后,其1 H NMR和13 C NMR图谱的化学位移有所变化,手性碳附近的某些原子所对应的吸收峰裂分为2组信号,分别对...用1 H NMR和13 C NMR研究了水溶性镧系位移试剂Sm-pdta对反式-4-羟基脯氨酸的手性识别.反式-4-羟基脯氨酸与Sm-pdta形成络合物后,其1 H NMR和13 C NMR图谱的化学位移有所变化,手性碳附近的某些原子所对应的吸收峰裂分为2组信号,分别对应反式-4-羟基脯氨酸的两种对映异构体.结果显示,对于反式-4-羟基脯胺酸,Sm-pdta是一个既方便又有效的手性位移试剂.展开更多
文摘A series of C_2-symmetrical chiral 2,5-bis(4'-alkyloxazolin-2-yl) thiophenes(thiobox) have been synthesized from thiophene-2,5-dicarboxylic acid by sequential amidation with achiral ethanolamine, conversion of hydroxyl to chloro group, and base-promoted oxazoline ringformation. As demonstrated by (-)-2,5-bis[4'-(S)-isopropyloxazolin-2'-yl] thiophene, these thioboxsystems exhibited remarkable chirality recognition of 1,1'-bi-2-naphthol giving rise to pronouncedshifts in the ~1H NMR signals of the latter axial chiral compound at the positions of C-3, C-4, C-5,and C-8.
文摘The lanthanide chelates of(l)-2,2-dimethyl-6-trifluoromethyl-7-oxa-6,8,8,9,9,10, 10,10-octafluoro-3,5-decanedione,Ln[(l)-CF_3CF_2CF_2OCF(CF_3)COCHCOC(CH_3)_3]_3(l-3a,Ln=Eu; 3b, Ln=Pr), are useful as ~1H NMR shift reagents for direct determination of enantiomeric composition of enantiomorphous alcohols. ketones and amines. With these substrates. l-3a induces shift difference similar to that induced by Eu(facam)_3 and Eu(hfbc)_3. However, due to the higher solubility of the chelates l-3a and l-3b in nonpolar organic solvent such as CHCl_3, CCl_4 and only one ~1H signal from l-3a and l-3b is observed. their application as the new chiral shift reagents seems promising. The spectral nonequivalence is also observed for dimethylsulfoxide in the presence of l-3a.
基金The Natural Science Foundation of China(21572240)
文摘目的研究手性分子与核磁共振(NMR)谱图之间的关系,为手性化合物研究提供参考。方法通过举例分析,阐述手性分子与NMR谱图之间的关系。如毗邻一个手性中心的亚甲基中的2个质子化学位移并非等价,—CH_2—基团实际上是—CH_aH_b—结构。此方法可以用来确定ee%(对映体过量)值。结果给出了应用手性衍生试剂、手性溶剂化试剂和手性位移试剂来确定ee%值的方法;此外,对手性螺环化合物的~1 H NMR谱图也进行了讨论。结论对于手性分子与NMR谱图之间关系的研究,可为通过NMR谱图表征手性分子提供参考。
文摘用1 H NMR和13 C NMR研究了水溶性镧系位移试剂Sm-pdta对反式-4-羟基脯氨酸的手性识别.反式-4-羟基脯氨酸与Sm-pdta形成络合物后,其1 H NMR和13 C NMR图谱的化学位移有所变化,手性碳附近的某些原子所对应的吸收峰裂分为2组信号,分别对应反式-4-羟基脯氨酸的两种对映异构体.结果显示,对于反式-4-羟基脯胺酸,Sm-pdta是一个既方便又有效的手性位移试剂.
