Pseudotetrahedral Polyhaloadamantanes as Chirality Probes:  Synthesis, Separation, and Absolute Configuration

• Published in: Journal of the American Chemical Society 2002-11, Vol.124 (45), p.13348-13349
• Main Authors: Schreiner, Peter R, Fokin, Andrey A, Lauenstein, Oliver, Okamoto, Yoshio, Wakita, Tsuneki, Rinderspacher, Christopher, Robinson, Gregory H, Vohs, Jason K, Campana, Charles F
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; General molecular conformation and symmetry; stereochemistry; Molecular properties and interactions with photons; Physics; Properties of molecules and molecular ions
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0274195

Pseudotetrahedral, conformationally as well as configurationally stable 1-bromo-3-chloro-5-fluoro- (4) and 1-bromo-3-chloro-5-fluoro-7-iodoadamantane (5) (and some related compounds) were prepared by our recently devised phase-transfer catalytic halogenation protocol; the optical antipodes of 4 were separated by HPLC on chiral phase in ee > 99%, and the absolute configurations were assigned by matching observed and computed circular dichroism spectra. Structure 5 is the first chiral aliphatic hydrocarbon containing all stable (nonradioactive) halogens; its structure was proven by NMR spectroscopy and by X-ray crystal data. We emphasize that the combination of experiment and theory is very powerful in assigning absolute configurations even for molecules without typical chromophors, with small values for the optical rotation, and without an atom at the stereogenic center.