The aim of our project is to build new catalysts for the asymmetric epoxidation of alkenes using ð-interactions as fundamental factors for the control of the facial selectivity. It was decided to employ cinchona alkaloid derivatives as the basic core of our catalysts. We envisage that the alkene would interact selectively with the aromatic rings of the catalyst to give the corresponding epoxide in good enantiomeric excess. Quinuclidine derived cataysts of simplified structures were synthesised to find the best conditions for the experiments using chiral cinchona derivatives. An important result to be taken into account in the development of the chiral catalysts was the influence of the counterion on the conversion rate. The triflate gave the highest epoxidation rates for trans-â-methylstyrene. The use of a mixture MeOH/ DMM/ H2O led to a two fold increase in reaction rate and is recommended to increase the van der Waals interactions between the aromatic rings of the catalyst and the alkene. New catalyst amd a new epoxidation protocol for the epoxidation of alkenes mediated by dioxiranes have been disscussed .Encouraging results have been obtained from this work.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2017. / This thesis is aimed at the investigation of the chiral discrimination process during diastereomeric salt formation, when selected cinchona alkaloids are exposed to racemic mixtures of tartaric acid derivatives. This research is based on the use of (+)‐cinchonine, (‐)‐cinchonidine, (‐)‐quinidine and (+)‐ quinine, which served as chiral bases, in order to resolve racemates of O,O'‐dibenzoyl‐tartaric acid (DBTA) and O,O'‐di‐p‐toluoyl‐tartaric acid (DTTA). Cinchona alkaloids were selected because of their abilities to form salts with the targeted acids. DBTA and DTTA are commonly used resolving agents to separate racemic bases via diastereomeric salt formation, and they are also commercially available and affordable chiral acids. Results were obtained from all combination but only the experiments with cinchonidine were included in this thesis, namely [CIND+][L‐DBTA‐], 2[CIND+][D‐DBTA2‐], [CIND+][LDTTA‐] and 2[CIND+][D‐DTTA2‐]∙2DMSO∙0.7H2O. Experimental analytical techniques, such as thermal analysis, powder X‐ray diffraction, and single crystal X‐ray diffraction were used to analyze the harvested diastereomeric salts. A correlation of molecular parameters derived from the structures and an investigation of the mechanism, which drives the resolution process were discussed. The thesis also summarizes the findings on 8 inclusion compounds of (‒)‐O,O'‐dibenzoyl‐(2R,3R)‐tartaric acid (L‐DBTA) and (‒)‐O,O'‐di‐p‐toluoyl‐(2R,3R)‐tartaric acid (L‐DTTA) or their racemic mixtures, (rac)‐ DBTA and (rac)‐DTTA, with DMSO and water: (rac)‐DBTA∙H2O, (rac)‐DBTA∙DMSO, L‐DBTA∙H2O, LDBTA∙ DMSO, (rac)‐DTTA∙H2O, (rac)‐DTTA∙DMSO, L‐DTTA∙H2O, and L‐DTTA∙DMSO. The discussed inclusion compounds were obtained serendipitously, as a product of the pre‐screening of suitable solvents to dissolve both the acids and the cinchona alkaloids during the discrimination experiments. Only few crystal structures of solvates of these two tartaric acid derivatives are known up to now, and fewer of these structures do exist when both the racemic and the enantiopure acid encapsulates the same solvent. The synthesis and structural analysis of these inclusion compounds contribute to the pool of available crystal structures when comparing chiral vs. achiral crystal forms of the same compounds.

Document incorrectly classified as a dissertation on title page (decision to classify as a thesis from NDSU Graduate School) / Organocatalysis is a field that has bloomed over the last decades. With the field’s promise of being able to mimic nature and afford products in a synergistic manner to traditional Lewis acid catalysis, several interesting discoveries have been made. Owing to the vastness of the field as it exists today, this document will focus on two main aspects; cinchona alkaloid (and derivatives) as used in common carbon-carbon bond forming reactions and kinetic resolution via 4-dimethyl aminopyridine-N-oxide derivative driven acylation. Kinetic resolution via organocatalysis has the potential to react one enantiomer of a racemic mixture without affecting the other. The highlight of this screening was an s factor of 9 which was produced using optimized conditions using a catalyst designated DMAPO-IV. There remains much to do in improving the system and elucidating the scope of this catalytic system this report details the efforts made thus far.

Synthesis of cyclodextrin derivatives for organocatalysis This doctoral thesis examines the preparation of new cyclodextrin (CD) derivatives suitable for organocatalysis. The aim of this work is to prepare monosubstituted and disubstituted CD derivatives as organocatalysts for different types of enantioselective reactions potentially performed in water. In addition, disubstituted CD derivatives require considering the potential mixture of regioisomers and pseudoenantiomers. Thus, this thesis is divided into several sections - preparation of CD precursors and derivatives for organocatalysis, preparation of pure regioisomers and pseudoenantiomers of disubstituted CDs and final application of CD derivatives in enantioselective reactions. Furthermore, this thesis also focuses on the molecular modeling of the prepared CD derivatives and on their catalytic activity in silico. The first section covers the preparation of new disubstituted CD precursors as pure regioisomers for organocatalysts, specifically to develop a new method for the preparation of heterodisubstituted AC regioisomers on the primary rim of α-CD. This section also includes the determination of the regioisomer ratios of common α-CD intermediates disubstituted on the primary rim to evaluate their potential as precursors in organocatalysis....

Stereodivergent and enantiodivergent pathways for the Friedel–Crafts reactions were computationally studied with DFT methods. This study aims to explain recently observed solvent-dependent regioselectivity, and enantioselectivity when cinchona catalyst is used. Deprotonation reaction, Frontier Kohn-Sham orbitals, dual descriptors, Mulliken charges, and Hirshfeld atomic charge for reactant were calculated and analyzed. The most probable position of electrophilic attack and nucleophilic attack in-silico predicted aligns with experimental observations. The calculation of the transition states on the anionic and neutral model in a vacuum show preference for the electrophilic attack in the para position. In comparison to the anionic system, the presence of potassium cation improves ortho/para selectivity and increases the energy barrier. For the key enantioselective step, 12 transition states were calculated which covers 4 representative product such: (R)-ortho, (S)-ortho, (R)-para, and (S)-para. The computational study suggests, that the presence of the cesium cation is essential for the arrangement of the reactant and catalyst in the transition state, which leads to observed selectivity.

Project I. Cinchona alkaloid-derived quaternary ammonium salts have been successfully used as phase-transfer catalysts, particularly in asymmetric alkylations. Our group applied this type of catalyst in the synthesis of β-hydroxy α-amino acids via aldol reactions and discovered that the Park-Jew catalyst afforded good yields and good enantiomeric excess of the syn diasteromers, but negligible diastereoselectivity. This project was therefore focused on the synthesis of novel cinchonidine-derived catalysts with the Park-Jew catalyst as the lead structure. The C3 position of cinchonidine nucleus was modified to achieve dimers and catalysts possessing electron-deficient alkyne and alkene moieties. Synthesized catalysts were tested in the asymmetric aldol reactions, with some of them yielding improvements relative to the Park-Jew catalyst. Project II. Celogentin C is a natural product that was isolated from the seeds of Celosia argentea by Kobayashi in 2001. It is the most potent inhibitor of the polymerization of tubulin from among the celogentin family. The novel bicyclic octapeptide structure contains unusual linkages between leucine β-carbon and indole C-6 of tryptophan and between tryptophan indole C-2 and imidazole N-1 of histidine. The project culminated in the first total synthesis of celogentin C. Reaction conditions were developed by synthesizing the left-hand ring and the right-hand ring separately, and the total synthesis was accomplished via a left to right strategy. Key transformations in the construction included intermolecular Knoevenagel condensation, radical conjugate addition, macrolactamization, and oxidative coupling.