Semester

Spring

Date of Graduation

2010

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Xiaodong M. Shi.

Abstract

Enantioselective intermolecular crossed-conjugate additions between nitroalkenes and alpha,beta-enals through a dual. Enantioselective intermolecular crossed-conjugated additions between nitroalkenes and enals were developed through Lewis base and iminium cation dual activation strategy. The optimal condition was suitable for a large group of nitroalkenes and enals with excellent yields and e.e.. Further derivatization led two diastereomers into single enantiomers of substituted pyrrolidine with excellent stereochemistry retention.;One-pot cascade Michael-Michael-Aldol condensation for diastereoselective synthesis of nitro-substituted cyclohexanes. A one-pot Michael-Michael-Aldol cascade reaction of proline Lewis base activated nitroalkenes and enones was developed for the preparation of nitro-vinyl-substituted cyclohexanes. Good yields and diastereoselectivity were observed. Further simple transformations easily lead to poly-N-heterocycles, which have great potential for the backbone synthesis of bioactive natural products.;Concise asymmetric synthesis of fully substituted isoxazoline-N-oxide through Lewis base catalyzed nitroalkene activation. A concise asymmetric synthesis of isoxazoline-N-oxides is reported through secondary amine Lewis base catalyzed nitroalkenes activation and sequential intermolecular condensation with aldehydes and ylides. Through the further application of camphor derived sulfur ylide, the enantiomeric enriched isoxazoline-N-oxides were prepared with excellent yields (up to 95%) and stereoselectivity (single trans isomers and up to 96% e.e.). The limitation of previous study had been successfully overcome. Further transformations of isoxazoline-N-oxide led to the gram-scale synthesis of a Clausenamide analogue, which has great potential for brain damage repair (Alzheimer's disease). Notably, this strategy had provided the all-cisgamma-lactam with four stereogenic centers in 4 steps, with excellent stereochemistry control. Asymmetric synthesis of other related analogues is underway.;One-step synthesis of substituted di-hydrofurans from Lewis base catalyzed three-component condensation. A one-pot synthesis of substituted di-hydrofuran was developed through Lewis base catalyzed three components cascade condensation between nitroalkene, aldehyde and 1,3-dicarbonyl compounds. The di-nucleophile moieties (1,3-dicarbonyl compounds) readily reacted with the nitro diene intermediate to provide the desired cyclization products with large substrate scope (>20 examples) and excellent diastereoselectivity (only trans isomers) in good to excellent yields (up to 96%). Further application of the di-hydrofuran towards useful synthetic building blocks is being studied with preliminary results.;One-pot asymmetric synthesis of substituted piperidines by exocyclic chirality induction. A highly efficient one-pot synthesis of substituted piperidines was developed through nitroalkene, amine, and enone condensation. The transformation was suitable for a large group of substrates, giving excellent yields and diastereoselectivity. Reactions using chiral amines revealed a chirality induction through the unusual exo-cyclic stereochemistry control, producing enantiomeric pure piperidines in simple steps. A six-member ring chair transition state was proposed to account for the stereoselectivity. Reactions involving chiral amine for the similar transition state are being investigated to extend the exo-cyclic chirality transfer strategy.;Anion bridged nanosheet from self-assembled G-quadruplexes. A novel, non-covalent polymeric nanosheet has been produced through functionalized Guanosine self-assembly via the cooperation of cations and corresponding anions. The nanosheet material was 3.0 nm in height 200 nm in average diameter. Its composition and structure have been characterized by solution NMR, solid-state NMR, powder XRD and AFM. Functionalized Guanosine had also been synthesized for further construction of nano scale supramolecular structures.

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