Pseudotetrahedral polyhaloadamantanes as chirality probes: synthesis, separation, and absolute configuration.
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.
Schreiner
Peter R
PR
Institut für Organische Chemie der Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany. prs@chem.uga.edu
Fokin
Andrey A
AA
Lauenstein
Oliver
O
Okamoto
Yoshio
Y
Wakita
Tsuneki
T
Rinderspacher
Christopher
C
Robinson
Gregory H
GH
Vohs
Jason K
JK
Campana
Charles F
CF