Stereomutation of axially chiral aryl coumarins.
Coumarins substituted by an aryl group in position 4 display restricted rotation about the Ar-C4 bond, giving rise to conformational or configurational enantiomers (atropisomers) when such a restricted motion leads to a C(1) symmetry. The dynamics of the stereomutation processes of these axial enantiomers was monitored by dynamic NMR, dynamic enantioselective HPLC, or racemization kinetics, depending on the activation energies involved. These results were further supported by DFT computations. In the two cases where the enantiomers were sufficiently long living as to be physically separated at ambient temperature, the absolute configuration was determined by means of a theoretical simulation of their electronic circular dichroism spectra (ECD).
Lunazzi
Lodovico
L
Department of Organic Chemistry A. Mangini, University of Bologna, Viale Risorgimento 4, Bologna 40136, Italy.
Mancinelli
Michele
M
Mazzanti
Andrea
A
Pierini
Marco
M
D002942:Circular Dichroism; D003198:Computer Simulation; D003374:Coumarins / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013237:Stereoisomerism
D003374:Coumarins