First asymmetric photosensitization in supercritical fluid. Exceptionally high pressure/density dependence of optical yield in photosensitized enantiodifferentiating isomerization of cyclooctene

The photosensitized enantiodifferentiating isomerization of (Z)-cyclooctene (1Z) in supercritical carbon dioxide has been performed for the first time. The critical control of the enantiomeric excess (ee) of chiral product, (E)-cyclooctene (1E), and even the switching of the product's chirality were achieved through a small change of pressure particularly in the low-density region near the critical density. Quantitative evaluation of these ee changes was achieved by estimating differential activation volumes between the diastereomeric transition states of the reaction.