Chiral β-Cyclocitral Schiff Bases: A Combined Spectroscopic and Theoretical Approach to a Twisted Enimine Structure

Article abstract of DOI:10.1021/ja00255a039

UV and CD spectra of eight β-cyclocitral Schiff bases rendered chiral by virtue of an asymmetrically substituted imine part have been measured and rationalized on the basis of force-field (MMP2) and quantum-mechanical (CNDO) calculations.They show the compounds to exist as a temperature- and solvent-dependent mixture of highly twisted s-cis and close to planar, but less stable s-trans conformers.Both ??* and n?* absorptions are unambigously assigned, the former in the UV spectra, and the latter in the CD spectra; however, only the sign of the n?* band correlates with the absolute conformation of the diene, being plus for M and minus for P helicity.