Thesis (M.S.)--University of Toledo, 2008. / Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science Degree in Chemistry." "A thesis entitled"--at head of title. Bibliography: leaves 58-62.

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La síntesi de sulfòxids quirals ha estat investigada teòricament considerant dos dels mètodes més avançats: l'oxidació asimètrica de sulfurs amb peròxid d'hidrogen catalitzada per vanadi i el mètode DAG. El mecanisme d'aquestes reaccions va ser explorat a nivell DFT (teoria del funcional de la densitat) en sistemes models. L'origen de l'enantioselectivitat en els sistemes reals va ser investigat emprant mètodes híbrids QM/MM (mecànica quàntica/mecànica molecular). L'estudi DFT sobre la sulfoxidació asimètrica catalitzada per vanadi va revelar que aquest procés segueix un mecanisme de transferencia directa d'oxigen en que el substrat s'oxida en una única etapa concertada. El catalitzador és un complex de vanadi(+V) en que l'oxidant es coordina al metall en mode hidroperoxo. Aquest complex catalitza el procés d'oxidació reduint la barrera energètica de 40.4 a 26.7 kcal/mol. L'estudi QM/MM del sistema real va demostrar que existiexen dos diastereòmers del catalitzador, etiquetats com a A i B, que catalitzen l'oxidació induint enantioselectivitats oposades. La coexistencia d'A i B en solució va permetre racionalitzar l'influència de l'estructura del lligand quiral sobre l'enantioselectivitat. L'estudi DFT del mètode DAG va revelar que la resolució cinètica dinàmica implicada en aquesta reacció segueix un mecanisme d'addició/eliminació. L'etapa clau és l'addició en que l'alcohol reacciona directament amb el clorur de sulfinil. Aquest procés implica un transferència d'hidrogen que és assistida per una base. La trimetilamina redueix la barrera d'aquest procés desde 26.8 a 12.2 kcal/mol. La base també catalitza la racemització del clorur de sulfinil reduint la barrera de la seva inversió piramidal desde 63.4 a 22.3 kcal/mol. La subsititució inicial del clor per la base va ser descartada. L'estudi QM/MM del sistem real confirmà que l'enantioselectivitat d'aquest procés es pot invertir amb facilitat emprant diferents bases no quirals, com la piridina o la colidina, tal com va ser observat experimentalment. El nostre estudi revelà que el paper estèric de la base és fonamental quan la piridina es canvia per colidina. Aquest canvi de base implica una inversió de la distribució quiral del volum estèric al voltant del sofre que provoca el canvi en el sentit de l'enantioselectivitat. / The synthesis of chiral sulfoxides has been theoretically investigated considering two of the most advanced methods: the vanadium-catalyzed asymmetric oxidation of sulfides with hydrogen peroxide and the DAG method. The mechanism of these reactions was explored at a DFT (Density Functional Theory) level on model systems. The origin of enantioselectivity in the real systems was explored applying hybrid QM/MM (Quantum Mechanics/Molecular Mechanics) methods. The DFT study on the vanadium-catalyzed asymmetric sulfoxidation revealed that this process follows a direct oxygen transfer mechanism in which the substrate is oxidized in a single concerted step. The catalyst is a oxo complex of vanadium(+V) with the oxidant coordinated to the metal as a hydroperoxo ligand. This complex catalyzes the oxidation process reducing the energy barrier from 40.4 to 26.7 kcal/mol. The QM/MM study on the real system showed that there are two possible diastereomers of the catalyst, labeled as A and B, that catalyze the oxidation inducing opposite enantioselectivities. The coexistence of A and B in solution explains the influence of the chiral ligand structure upon enantioselectivity. The DFT study on the DAG method revealed that the dynamic kinetic resolution involved in this transformation follows an addition/elimination mechanism. The key step is the addition in which the alcohol reacts directly with the sulfinyl chloride. This process implies a hydrogen transfer assisted by the base. Triethylamine reduces the barrier of this process from 26.8 to 12.2 kcal/mol. The base also catalyzes the racemization of the sulfinyl chloride reducing the barrier of its pyramidal inversion from 63.4 to 22.3 kcal/mol. The substitution of chlorine by the base was discarded. The QM/MM study of the real system confirmed that the enantioselectivity of this reaction can be easily reversed using different non chiral bases, like pyridine or collidine, as experimentally observed. Our study showed that the steric role of the base becomes critical when pyridine is replaced by collidine. This modification of the base implies an inversion of the chiral distribution of steric bulk around sufur that induces the reversal of enantioselectivity.

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This thesis describes the synthesis of a number of hydroxy vinylsulphoxides and sulphones by a high pressure modification of the Baylis-Hillman reaction, together with their directed hydrogenation catalysed by rhodium catalysts. A detailed kinetic analysis of a number of the hydrogenation reactions carried out by numerical analysis is also presented. Chapter 1 serves as an introduction to directed hydrogenation and the chemistry of sulphur containing compounds. Chapter 2 details the synthesis of catalysts and substrates used in hydrogenation reactions. The use of high pressures to improve the performance of the Baylis-Hillman reaction is included. Chapter 3 details the products and the selectivity obtained in the hydrogenation of hydroxy vinylsulphoxides and sulphones. The kinetic resolution of 3-phenyl-2-(phenylsulphonyl)- propene-3-ol using a DiPAMP rhodium catalyst is described. Chapter 4 details the numerical analysis of the kinetics of the hydrogenation reactions of a number of hydroxy vinylsulphoxides and sulphones.

Thesis (M.Sc. (Organic Chemistry))--Mahidol University, 1983.

Thesis (M.Sc. (Organic Biochemistry)--Mahidol University, 1984.

Thesis (M.Sc. (Organic Chemistry))--Mahidol University, 1983. / A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science (Organic Chemistry) in the Faculty of Graduate studies of Mahidol University, 1983.

Thesis (M.Sc. (Organic Chemistry))--Mahidol University, 1984.

Thesis (M.Sc. (Organic Chemistry)) -- Mahidol University, 1978. / Supported by the University Development Commission.