The primary goal of this project is aimed to improve the understanding and control of diastereofacial selectivity in asymmetric organic reactions. The conformational preferences of chiral alkenes will be determined through the J averaging method with the variable temperature NMR technique. The free energy differences for the two diastereomeric transition states will be estimated through the isomeric products ratio. The stereochemistry of the products and the conformational preferences of the starting materials should form a basis for the understanding of the important factors in the transition states, therefore the control of the pi-facial selectivity. Based on our preliminary results, the modern high field NMR technique is well suited to study the relative conformational stabilities of chiral alkenes. Although the significance of the conformational profiles of the chiral alkenes has been recognized for sometime, presently experimental techniques are either difficult to interpret or cannot be applied to a wide range of reagents. The information obtained through the VT NMR study should prove to be of great value and interest to the chemical community. Previous studies aimed at the understanding of electronic effects have concentrated on comparing C-C bonds with slightly different polarities. This project employs substrates which have either a C-H bond or a C-0 bond anti to the attacking nucleophile. Thus the properties of the implied orbital interaction in the transition state are different enough to allow little ambiguity in the final analysis of the results.
