Document Type
Article
Publication Date
5-1-2014
Published In
Nature
Abstract
One of the most well-recognized stereogenic elements in a chiral molecule is an sp(3)-hybridized carbon atom that is connected to four different substituents. Axes of chirality can also exist about bonds with hindered barriers of rotation; molecules containing such axes are known as atropisomers(1). Understanding the dynamics of these systems can be useful, for example, in the design of single-atropisomer drugs(2) or molecular switches and motors(3). For molecules that exhibit a single axis of chirality, rotation about that axis leads to racemization as the system reaches equilibrium. Here we report a two-axis system for which an enantioselective reaction produces four stereoisomers (two enantiomeric pairs): following a catalytic asymmetric transformation, we observe a kinetically controlled product distribution that is perturbed from the system's equilibrium position. As the system undergoes isomerization, one of the diastereomeric pairs drifts spontaneously to a higher enantiomeric ratio. In a compensatory manner, the enantiomeric ratio of the other diastereomeric pair decreases. These observations are made for a class of unsymmetrical amides that exhibits two asymmetric axes-one axis is defined through a benzamide substructure, and the other axis is associated with differentially N,N-disubstituted amides. The stereodynamics of these substrates provides an opportunity to observe a curious interplay of kinetics and thermodynamics intrinsic to a system of stereoisomers that is constrained to a situation of partial equilibrium.
Recommended Citation
K. T. Barrett, A. J. Metrano, Paul R. Rablen, and S. J. Miller.
(2014).
"Spontaneous Transfer Of Chirality In An Atropisomerically Enriched Two-Axis System".
Nature.
Volume 509,
Issue 7498.
71-75.
DOI: 10.1038/nature13189
https://works.swarthmore.edu/fac-chemistry/102
Comments
This work is a preprint that has been provided to PubMed Central courtesy of Nature Publishing Group.
The final publication version can be freely accessed courtesy of Springer Nature's SharedIt service.