Diastereoselective synthesis of cyclopropanols and their use as homoenolates

Chapter one focuses on the development of an efficient, one-pot asymmetric approach to synthesizing pyranones. Asymmetric addition of dialkylzinc reagents mediated by the chiral amino alcohol ligand, (-)-MIB, to 2-furfurals proceeded to give the corresponding furyl alkoxides in high enantioselectivity. Direct addition of water and N- bromosuccinimide (NBS) resulted in formation of the corresponding pyranone in high enantioselectivities and moderate to good yields. In addition to commercially available zinc nucleophiles, functionalized dialkylzinc reagents were also found to be amenable to this procedure in order to synthesize more highly substituted pyranones.;Chapter two describes the synthesis of trans-1,2-substituted cyclopropanols using alpha-haloaldehydes and the gem-dizinc reagent, bis(iodozincio)methane. Reaction of this dizinc reagent with both alpha-bromo and alpha-chloroaldehydes yielded the corresponding cyclopropanols with similar yields and diastereoselectivities. Use of an enantioenriched alpha-chloroaldehyde was also found the give the desired product with no loss in enantioselectivity. Reactions were designed in order to probe the mechanism by which such high diastereoselectivity was obtained.;Chapter three discusses the use of 2-substituted cyclopropanols as masked carbonyl compounds. Due to the strained nature of the three-membered ring, cyclopropanols are subject to ring opening reactions to generate transient homoenolates, which are otherwise difficult to access. This project describes a mild method for the palladium-mediated cross-coupling of reactive aldehyde homoenolates with aryl bromides. Treating trans-2-substituted cyclopropanols with Pd(OAc)2 (5 mol %), QPhos (10 mol %), and triethylamine leads to the cross coupling of both electron-rich and electron-poor aryl bromides to provide the beta-arylated aldehydes in good yield (59-89%). This procedure is easily scalable and applicable to enantioenriched cyclopropanols, where cross-coupling was found to proceed without loss of stereochemistry.;In Chapter 4, the synthesis of tri(aryl)benzene compounds via the Suzuki cross- coupling of 1-bromo-3-chloro-5-iodobenzene with boronic acids is explored. Compounds such as 1,3-bis(1-naphthyl)-5-(2-naphthyl)benzene have been found to form stable, high density glasses upon vapor deposition. The goal of this project is the systematic synthesis of tri(aryl)benzene compounds and the investigation of how chemical structure affects the ability of a molecule to undergo glass transition. Our collaborators in the Fakhraai group have been testing these compounds for the presence of glass transitions and also plan on determining whether these compounds can form stable glasses upon vapor deposition.