1. Building Enantioselective Ligands: New Frontiers with Oxazolines
Christopher J. A. Daley, Department of Chemistry and Biochemistry, University of San Diego, San Diego, CA
While many organic reactions are catalyzed with good to excellent enantioselectivity, a vast number of improvements are still required to (i) expand the set of reactions that a specific complex can catalyze, (ii) expand the substrate range of catalyzed reactions, (iii) tolerate a wider set of functional groups, and (iv) decrease the cost of the catalysts. The ongoing design and synthesis of new chiral ligands continues to have a positive impact by reducing the extent of these problems. The fundamental goal of this project is to make a series of new multifunctional chiral ligands that, in conjunction with appropriate metals, catalyze numerous organic reactions with increased enantioselectivity.
For enantioselective catalysis to succeed for our system, the oxazoline pendent arms must be chiral and should have high thermal stability in order to condense with the isoindoline synthon. We have presently synthesized our first chiral ligand system as a zinc(II) complex. It has been characterized by multinuclear NMR, electrospray mass spectrometry, and atomic absorption. Our next goals will be to (a) prepare the ligand in higher yield, (b) synthesize a number of metal complexes, and (c) determine the enantioselectivity of the metal complexes by performing a standard suite of metal-mediated organic reactions.