This research proposal describes experiments that will incorporate Corey's postulate of formyl CH-O hydrogen bonding as a new design element for chiral copper(II) catalysts for the aldol reaction. The cationic bis(oxazoline) ("box") and pyridyl bis(oxazoline) ("pybox") complexes function as efficient catalysts for the aldol reactions involving chelating substrates. The wealth of knowledge gained regarding the nature of the catalyst/substrate organization in these reactions makes them an ideal proving ground for new concepts such as the formyl CH-X hydrogen bond. The first part of the proposal delineates the development of a series of bidentate amine ligands with tethered alkoxides that will bind non-chelating aldehydes and engage in a formyl CH-O hydrogen bond. The resultant catalyst-substrate complex will have a structure reminiscent of the chelate assembly postulated to form between the copper(II)-box catalyst and a chelating electrophile, and should thus show a similar sense of asymmetric induction. The latter portion of the proposal discusses how formyl CH-X hydrogen bonding can be used to effect enantio-complimentarity by use of ligands that mimic the square pyramidal geometry of the copper(II)-pybox catalysts. Through placement of the hydrogen bond acceptor on the metal center at either an equatorial or apical site, the mode of binding of an aldehyde will be reversed as will the sense of asymmetric induction. The successful execution of the experiments described within will evaluate the viability of formyl CH-X hydrogen bonding as a conformational constraint for reactions catalyzed by new and novel copper(II) Lewis acids. This will in turn lead to the discovery of new selective reactions for the formation of biologically relevant organic molecules.
|Effective start/end date||6/15/99 → …|
- National Institutes of Health: $30,256.00
- National Institutes of Health: $32,416.00
- Biochemistry, Genetics and Molecular Biology(all)