From catalysis to anion recognition

Abstract

<bold>Part 1. A novel approach to enantioselective hydroacylation.</bold> A known methodology for hydroacylation of monosubstituted alkenes utilizing 2-amino-3-picoline as a temporary directing group was studied in order to broaden its scope and enable access to chiral products. This transformation was expanded to include intramolecular process of prochiral 1,1-disubstituted alkenes, which leads to the formation of six and seven-membered cyclic β-substituted ketones. Various approaches to induce enantioselectivity were investigated and promising results were obtained with a chiral derivative of 2-amino-3-picoline. <bold>Part 2. Three hydrogen bond donor catalysts.</bold> Inspired by Nature's three pronged oxy anion holes, the first study on the effect of a third hydrogen bond on catalysis was carried out. Model compounds based on a 1,3,5-triarylbenzene core containing two or three hydrogen bond donors were designed and synthesized. Kinetic studies of various reactions showed that the catalysts that can provide three hydrogen bonds often lead to much faster rates and give higher selectivities compared to their two hydrogen bond donor analogs. <bold>Part 3. Functionalized 1,3,5-triarylbenzenes as anion receptors.</bold> Anion binding affinities of structural analogs of the catalysts in Part 2 were studied. A neutral tris-thiourea derivative was discovered to be a selective dihydrogen phosphate receptor in aqueous solutions. Model compounds with one and two thiourea arms were synthesized. UV-VIS, IR and NMR spectra along with binding constant determinations elucidated the mode of interaction of various anions to these thiourea compounds. Fluorescent and bifunctional receptors were also studied to further increase the selectivity for dihydrogen phosphate.