title: Terpenols as substituents for the diastereoselective formation of enantiomerically pure triple lithium-bridged helicate type-coordination compounds.
abstract: The terpenols l(-)-borneol, (1S2S3S5R)-3-pinanol, (-)-menthol, and (-)-myrtenol are easily available chiral alcohols for the preparation of enantiomerically pure catechol esters -H2. Those ligands are used for the hierarchical assembly of triple lithium-bridged dinuclear titanium(iv) triscatecholate helicates Li[Li3()6Ti2]. In solution, the dimeric species are in a solvent dependent equilibrium with the monomer Li2[()3Ti]. The equilibrium is studied by (1)H NMR. CD spectroscopy indicates that the configuration at the complex units of the enantiomerically pure dimeric α-chiral derivatives Li[Li3()6Ti2] is opposite to the configuration of the monomers Li2[()3Ti]. For the γ-chiral complex Li2[()3Ti] only a de of 25% is observed and in this case no interpretation of the mechanism of stereocontrol is possible.
authors.affiliation: Institut für Organische Chemie, RWTH Aachen, Landoltweg 1, 52074 Aachen, Germany. markus.albrecht@oc.rwth-aachen.de.
authors.forename: M
authors.initials: M
authors.lastname: Albrecht
authors.forename: E
authors.initials: E
authors.lastname: Isaak
authors.forename: H
authors.initials: H
authors.lastname: Shigemitsu
authors.forename: V
authors.initials: V
authors.lastname: Moha
authors.forename: G
authors.initials: G
authors.lastname: Raabe
authors.forename: R
authors.initials: R
authors.lastname: Fröhlich