描述了24元大环的合成,其中作为柔性类似物的刚性x吨单元(X)和/或二苯醚单元(D)通过脲基连接。对于环化步骤,已获得所有四种可能的组合(XXX,XXD,XDD,DDD),产率为40-72%。在两种情况下,还分离了相应的环状六聚体(XXDXXD,XXXXXX)。两种化合物的特征是通过游离三脲的单晶X射线分析(XXD,XDD)和一个实例(DDD)通过与氯化四丁铵的络合物表征。它显示了大环中心的氯阴离子,由六个NH ... Cl-氢键保持。与其他各种阴离子的相互作用已通过1 H NMR进行了研究。已经通过紫外分光光度法测量了所有三聚体的氯化物,溴化物和乙酸盐的络合常数。已经进行了分子动力学模拟以确定游离受体在氯仿和乙腈中的构象。他们表明,在氯仿中,酰胺键的反式->顺式异构化有时会促进分子内氢键键合,从而控制大环的构象,而在乙腈(用于络合度测量的溶剂)中,连接尿素NH质子的排列适当。阴离子的络合,但是它们的强溶剂化作用与络合相反。
Varied flexibility: Cyclic oligoureas are formed by using anions as templates. Linking of six xanthene and/or diphenyl ether fragments by urea groups leads to the formation of five macrocyclic compounds with a 48‐membered ring with variable flexibility (see picture). Their interaction with anions shows a strong influence of acetate and chloride ions on the cyclization from four precursor molecules
Cyclic triureas—synthesis, crystal structures and properties
作者:Denys Meshcheryakov、Françoise Arnaud-Neu、Volker Böhmer、Michael Bolte、Véronique Hubscher-Bruder、Emilie Jobin、Iris Thondorf、Sabine Werner
DOI:10.1039/b718114k
日期:——
analysis of the free triurea (XXD, XDD) and one example (DDD) by its complex with tetrabutylammonium chloride. It shows the chloride anion in the centre of the macrocycle, held by six NH...Cl- hydrogen bonds. The interaction with various other anions has been studied by 1H NMR. Complexation constants for chloride, bromide and acetate have been measured for all trimers by UV spectrophotometry. Molecular dynamics
描述了24元大环的合成,其中作为柔性类似物的刚性x吨单元(X)和/或二苯醚单元(D)通过脲基连接。对于环化步骤,已获得所有四种可能的组合(XXX,XXD,XDD,DDD),产率为40-72%。在两种情况下,还分离了相应的环状六聚体(XXDXXD,XXXXXX)。两种化合物的特征是通过游离三脲的单晶X射线分析(XXD,XDD)和一个实例(DDD)通过与氯化四丁铵的络合物表征。它显示了大环中心的氯阴离子,由六个NH ... Cl-氢键保持。与其他各种阴离子的相互作用已通过1 H NMR进行了研究。已经通过紫外分光光度法测量了所有三聚体的氯化物,溴化物和乙酸盐的络合常数。已经进行了分子动力学模拟以确定游离受体在氯仿和乙腈中的构象。他们表明,在氯仿中,酰胺键的反式->顺式异构化有时会促进分子内氢键键合,从而控制大环的构象,而在乙腈(用于络合度测量的溶剂)中,连接尿素NH质子的排列适当。阴离子的络合,但是它们的强溶剂化作用与络合相反。
Cyclic tetraureas with variable flexibility – synthesis, crystal structures and properties
作者:Denys Meshcheryakov、Françoise Arnaud-Neu、Volker Böhmer、Michael Bolte、Julien Cavaleri、Véronique Hubscher-Bruder、Iris Thondorf、Sabine Werner
DOI:10.1039/b808773c
日期:——
for both compounds and intramolecular hydrogen bonds for the two structures of XXXD, but surprisingly no direct intermolecular hydrogen bonds between the macrocyclic tetraurea molecules. The interaction with various anions was studied by (1)H NMR spectroscopy. Stability constants for all tetramers were determined by UV spectroscopy for complexes with chloride, bromide, acetate and dihydrogenphosphate