Probing the stereochemistry of the photo-Favorskii rearrangement

ORGN 638

Marina Rubina,, Kenneth F. Stensrud, and Richard S Givens, Department of Chemistry, University of Kansas, 5010 Malott Hall, 1251 Wescoe Hall Dr, Lawrence, KS 66045
The stereochemistry of the migrating carbon in the photo-Favorskii rearrangement of α-substituted p-hydroxybutyrophenones has been investigated for a series of diastereomeric carboxylates and sulfonates. Positioning the leaving group on a stereogenic center provides an opportunity to probe steric factors and the stereochemical consequences of the rearrangement to the p-hydroxyphenylbutanoic acid. Questions regarding substrate-chromophore recombination, configurational relaxation, and enantiomeric configuration and purity of the rearranged chromophore have been addressed. Comparative quantum yields of the diastereomeric pairs in various solvent systems have been investigated as well as the preparative synthetic routes to homochiral p-hydroxybutyrophenone-protected carboxylates will be presented.