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 aC1 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 dicroism spectra (ECD).
Stereomutation of Axially Chiral Aryl Coumarins / L. Lunazzi; M.Mancinelli; A.Mazzanti; M.Pierini. - In: JOURNAL OF ORGANIC CHEMISTRY. - ISSN 0022-3263. - STAMPA. - 75:(2010), pp. 5927-5933. [10.1021/jo101261k]
Stereomutation of Axially Chiral Aryl Coumarins
LUNAZZI, LODOVICO;MANCINELLI, MICHELE;MAZZANTI, ANDREA;
2010
Abstract
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 aC1 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 dicroism spectra (ECD).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
