Azq. Khan et J. Sandstrom, ENANTIOMER AND DIASTEREOISOMER RESOLUTION, ROTATIONAL BARRIERS, AND CD AND UV SPECTRA OF SOME TWISTED PUSH-PULL ETHYLENES, Perkin transactions. 2, (7), 1994, pp. 1575-1579
Suitably substituted twisted push-pull ethylenes capable of existing e
ither as mixtures of achiral diastereoisomers or as pairs of enantiome
rs have been resolved, in the first case into diastereoisomers by HPLC
on silica, in the second case into enantiomers by chiral chromatograp
hy on tris(phenylcarbamoyl)cellulose. Free energy barriers to rotation
through the planar state have been determined by monitoring respectiv
ely the rate of diastereoisomer interconversion and the rate of racemi
zation at elevated temperatures. UV and CD spectra have been analysed
with the aid of CNDO/S calculations for simplified models.