ABSTRACT
Five racemic dissymmetric bis(pyridyl) ligands based on 2,8- or 3,9-difunctionalised Tröger's base derivatives have been synthesised. Only those derived from a 2,8-difunctionalised scaffold were found to undergo selective self-assembly to discrete self-assembled dinuclear metallosupramolecular aggregates of rhomboid shape upon coordination to cis-protected Pd(2+) or Pt(2+) ions, as evidenced by ESI mass spectrometry, NMR spectroscopy and single-crystal X-ray diffraction. Interestingly, these processes were found to be highly diastereoselective leading to the formation of C(2v)-symmetric heterochiral assemblies in a self-discriminating manner.
ABSTRACT
An enantiomerically pure bis(bipyridine) BINOL ligand was synthesized which was functionalized with an iodine substituent in its periphery. Using this halogen function, the ligand was immobilized on a commercially available polystyrene gel via Suzuki cross-coupling. The functionalized gel was found to be effective in the chiral resolution of similar bis(bipyridine) ligands based on a Tröger's base core.
ABSTRACT
A racemic bis(nitrile) ligand based on the Tröger's base scaffold self-assembles into an achiral dinuclear heterochiral rhomb in a diastereoselective self-discrimination process; this occurs upon coordination to (dppp)Pd(OTf)(2) as evidenced by nmr spectroscopy and X-ray crystal structure analysis.
ABSTRACT
Two racemic derivatives of Tröger's base, the 2,8-diboronic acid ester 6 and the 3,9-dibromo-substituted derivative 5, were synthesized and successfully resolved by HPLC on a chiral stationary Whelk-01 phase on a semipreparative scale, thereby giving rise to both enantiomers in a pure form. These functionalized C(2)-symmetric building blocks are valuable precursors for a variety of further applications. Their absolute configurations were determined by comparison of their quantum chemically calculated CD and UV/Vis spectra with the experimental ones and were independently confirmed by X-ray diffraction analysis.
