Doctor of Philosophy / Department of Chemistry / Christopher J. Levy / The helix is an important chiral motif in nature, there is increasing development in field of helical transition metal complexes and related supramolecular structures. Hence, the goals of this work are to apply the principles of helicity in order to produce metal complexes with predictable molecular shapes and to study their properties as asymmetric catalysts. Computational studies suggest that the (1R,2R)-cyclobutyldiamine unit can produce highly twisted salen complexes with a large energy barrier between the M and P helical forms. To test this prediction, the tartrate salt of (1R,2R)-cyclobutyldiamine was synthesized and condensed with a series of saliclaldehydes to produce novel salen ligands. The salicylaldehydes chosen have extended phenanthryl or benz[a]anthryl sidearms to encourage formation of helical coordination complexes. These ligands were metallated with zinc, iron and manganese salts to produce salen metal complexes which were characterized by NMR analysis, high-resolution mass spectrometry, and IR spectroscopy. A second ligand type, neutral bis(pyridine-imine) has also been synthesized from (1R,2R)-cyclobutyldiamine and quinolylaldehydes. The synthesis of bis(pyridine-imine) ligands was conducted using greener method, solvent assisted grinding. These ligands, in-situ with nickel metal salts, showed good catalytic activity for asymmetric Diels-Alder reactions. The third ligand type studied was chiral acid-functionalized Schiff-base ligands. These were synthesized by the condensation of 3-formyl-5-methyl salicylic acid and (1R,2R)-cyclobutyldiamine. With this type of ligand, there is possibility of producing both mono and dinuclear metal complexes. In our studies, we were only able to synthesize mononuclear complexs. These were tested as catalysts for asymmetric direct Mannich-type reaction, but were found to be ineffective.

The synthetic strategy of this study mainly depends upon the asymmetric desymmetrization of meso norbornene type an anhydride. Asymmetric desymmetrization was achieved by using chinchona alkaloids under kinetically controlled conditions. The resultant mono ester carboxylic acid was epimerized to trans configuration. Subsequent esterification followed by lithium aluminum hydride reduction afforded the first chiral diol ligand with 98 % ee. Transformation of diol to corresponding trans diamine was achieved via Mitsunobu-Gabriel combination. The resultant diamine was first transformed into salen type ligand with 3,5-di-tert-butyl-2-hydroxybenzaldehyde. Throughout this process, no racemization was observed and all the ligands tested in asymmetric reactions have 98 % ee value. The second part of the thesis involves the asymmetric test reactions of the chiral ligands to check the effectiveness of them. The first testing method was diethylzinc addition to benzaldehyde. The ligands showed moderate effectiveness. The salen type ligand was tested in asymmetric epoxidation and aziridination reactions and it showed good effectiveness. Another applied method was desymmetrization of meso 2-cyclohexene-3,4-diol in which 2-(diphenylphosphino)benzoic acid attached trans-diol and trans-diamine type ligands were tested. Since norbornene type strained bicyclic systems are available in ring opening methathesis polymerization (ROMP) reactions, trans-diamine was subjected to ROMP to get an enlarged macromolecular system

Functionalized cyanophosphates are important starting materials for the synthesis of beta-lactam ring moiety of beta-lactam antibiotics. The cyanophosphates are synthesized starting from easily available acylphosphonate and ethylcyanoformate. Acylphosphonates are synthesized starting from acylchloride and trimethylphosphite. Addition of acylphoshonate to ethylcyanoformate furnishes the cyanophosphate with the quaternary center.