| My Ph.D. dissertation describes three different external influences on pericyclic reactions: (1) ionic liquids, (2) Lewis acids and (3) bis(oxazoline)-Cu(II) complexes. (1) Ionic liquids deliver enhanced rates and endo/ exo selectivities on the Diels-Alder reaction. The goal is to establish a firm understanding of the molecular interactions that give rise to the observed rate and selectivity enhancements. In order to accomplish our goal, we have used density functional theory methodology, specifically the Becke three parameter with Lee, Yang and Parr corrections at the 6-31G(d), to describe short-range effects, and have created new force field parameters using CHARMM to allow faster classical computations and explore bulk phase effects. (2) Lewis acids are known to influence strongly the rate, regio, endo/ exo, diastereofacial and enantio selectivities of the Diels-Alder reaction. Specifically, asymmetric catalysis using chiral Lewis acids provides a crucial tool in the enantioselective synthesis of chiral organic compounds. Uncovering the differential forces between the ground and transition structures with chiral Lewis acids is a perquisite step towards the creation of more effective enantioselective catalysts. Our efforts focus upon a novel combination of two specific intermolecular interactions between boron Lewis acids and Diels-Alder transition structures. Quantum mechanical calculations along with kinetic isotope effects are used in conjunction to elucidate these specific interactions. (3) Cu(II) functions effectively as a Lewis acidic center that has proven to control the stereoselectivity of a wide range of organic reactions. Specifically, bis(oxazoline) copper(II) complexes operate as enantioselective Lewis acid catalysts for carbocyclic and hetero Diels-Alder reactions. We have used quantum mechanical calculations in order to determine how ligand field strength influences Cu(II) coordination and ultimately the stereoselectivity of organic reactions. |
