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Chiral Cavities (chiral + cavity)
Selected AbstractsChemInform Abstract: Substrate Control by Means of the Chiral Cavity of Prolinamide Derivatives of Cholic Acid in the Organocatalyzed Michael Addition of Cyclohexanone to Nitroolefins.CHEMINFORM, Issue 12 2009Gian Luigi Puleo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Metal-Complex Assemblies Constructed from the Flexible Hinge-Like Ligand H2bhnq: Structural Versatility and Dynamic Behavior in the Solid StateCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2004Koichi Yamada Dr. Abstract Novel metal-complex assemblies constructed from the flexible hinge-like ligand H2bhnq (H2bhnq=2,2,-bi(3-hydroxy-1,4-naphthoquinone)) have been synthesized. The X-ray crystal structures of these compounds reveal that four types of architectures are accessible by variation of the metal ions. In copper(II) compounds 1,3, the chelating bhnq2, ions bridge copper(II) centers to form one-dimensional zigzag chains. The chains of 1,3 are arranged by hydrogen-bonding interactions and stacking interactions to produce porous structures. Cobalt(II) and zinc(II) compounds 4 and 5 form one-dimensional helical chains. In 4 and 5, the crystal packing induces spontaneous resolution of the helical chains with chiral cavities formed perpendicular to the helices. Nickel(II) compounds 6 and 7 form cyclic tetramers. The fourth architecture, a dimer (compound 8), is obtained by the reaction of zinc(II) and bhnq2, in MeOH. In these compounds, changes of the dihedral angles and the metal-coordination mode of the bhnq2, ion induce the structural versatility. The assemblies of the zigzag chains of the copper(II) compounds exhibit reversible vapochromic behavior. UV/Vis, powder X-ray diffraction, EPR, and adsorption isotherm measurements indicate that this vapochromic behavior is based on the hinge-like flexibility of the bhnq2, ion. [source] Asymmetric Epoxidation of Terminal Olefins with Binaphthyl Strapped Porphyrin Catalysts: (-( Stacking Interaction and Steric Effects on the EnantioselectivitiesCHINESE JOURNAL OF CHEMISTRY, Issue 5 2009Qizhi REN Abstract Two binaphthyl strapped porphyrins with similar chiral auxiliaries 1b and 2b were used as efficient catalysts for asymmetric epoxidation of both styrene derivatives and non-aromatic olefin substrates. Theoretical calculation of styrene approach to both catalysts has been performed. The subtle difference of the chiral cavities between two porphyrins has been analyzed by 1H NMR. The ,-, stacking interaction between aromatic substrates and catalysts might be one factor for the dramatic different enantioselectivities. Besides, the steric effect of the binaphthyl handle of 1b and 2b also causes the high ee values for non-aromatic olefin epoxidations. [source] Chiral Crystal Structure of Racemic Binaphthyl Poly(ether ketone) MacrocyclesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2005Xing Wang Abstract Summary: The crystal structure of rigid, hollow, racemic binaphthyl poly(ether ketone) macrocycles has been elucidated by single crystal X-ray analysis. Multitudinal interactions were identified within the chiral space group P212121. The structural analysis revealed that this macrocyclic compound contains an elliptic chiral cavity with a size of 9.80,×,5.18 Å, which is similar to that of cyclodextrins. The knowledge about the interaction sites and the structure of the binaphthyl-based macrocycle provides a unique opportunity to understand its molecular or chiral recognition properties. Space-filling representation of the single (R)-macrocycle. [source] | ||||||||||