The presented master thesis is devoted to the investigation of reaction intermediates in homogeneous gold catalysis. Electrospray ionization mass spectrometry (ESI-MS) was used as the primary research technique in this study. Delayed reactant labeling was used as the main method. I have focused mainly on the hydration of 1-phenyl-1-propyne catalyzed by the gold complex [Au(IPr)(MeCN)]BF4 (IPr = 1,3-bis(2,6-di-iso-propylphenyl)imidazol-2- ylidene). I have detected two main intermediates containing one or two gold atoms, respectively (monoaurated and diaurated intermediate). I have obtained rate constants for the degradation of the reaction intermediates and their half-lives. I have derived kinetic isotope effects for the formation and the decomposition of the detected intermediates. I have shown that the kinetics of the degradation of both intermediates is identical, therefore I conclude that hydration of alkynes catalyzed by gold complex [Au(IPr)(MeCN)]BF4 proceeds most probably via neutral monoaurated intermediates. These neutral intermediates are detected by ESI-MS as protonated (monoaurated intermediate) or tagged by a second gold cation (diaurated intermediate). Key words: gold catalysis, reaction intermediates, electrospray ionization, mass spectrometry.

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In the last century, no less than five nobel prizes have been awarded for the construction of carbon-carbon bonds : The Grignard reaction (1912), the Diels-Alder reaction (1950), the Wittig reaction (1979), Olefin metathesis (2005) and palladium cross-coupling reactions (2011). The latter two are transition metal catalyzed transformations and their impact on the synthesis of pharmaceutically active compounds, bulk chemicals, fine chemicals, high tech materials as well as agricultural chemicals has been phenomenal. These reactions have changed the way the scientific community views the science of synthesis. Unlike palladium, gold has long been considered to be an expensive and inert metal and therefore, research on Au catalysis was scarse until the begining of the new millenium. Once the scientific community realized the treasure trove of reactivity that gold had to offer, the number of chemical transformations as well as total syntheses involving Au(I)/Au(III) catalysis has sky rocketed. A methodology initially developped by Toste and coworkers has shown that intramolecular addition of a silyl enol ether on alkynes proceeds via a 5-exo¬-dig¬ process. In the first part of this thesis, we will discuss how the ancilary ligand on Au(I) species can influence pathway selectivity for these cyclizations, therefore opening the door to selective 6-endo-dig cyclizations to generate fused carbocycles. With biological processes as well as other competing processes becoming ever more efficient, the future of chemical synthesis is threatened. If it is to survive, the focus of new chemical transformations will have to be on the cost and the greeness of the process. In the second part of this thesis, we will demonstrate how Ag(I) and Cu(I) complexes can offer even better 6-endo-dig¬ selectivity than analogous Au(I) complexes. Silver is about 56 times less expensive than gold, and copper is about 453 times less expensive than gold. Due to the greatly increased selectivity as well as the diminished cost of the catalysts, we have provided access to an attractive 6-endo-dig¬ cyclization process.

Gold catalysis has attracted much attention within the chemical community in recent years, and its importance as a synthetic tool has only started to be uncovered. This thesis describes the development of a gold(I) catalyzed transformation and its application to the synthesis of a structurally unique Lycopodium alkaloid, Magellanine. Although there have been a few reports on the synthesis of the magellanane core to date, the approach described herein would represent a new and efficient strategy to construct the angularly fused tetracyclic core. The 5 exo dig/Prins reaction that would be the key step of the synthesis was first developed and studied on a model substrate, enabling the verification of the hypothesis that this transformation could indeed form the A and B rings of Magellanine and be applied to its synthesis. This reaction formed the tricyclic products in good yields and in good exo:endo ratios. The synthesis of Magellanine was undertaken, but problems of isomerization prevented the synthesis of the desired 5 exo dig/Prins substrate, which contained the C and D rings of Magellanine with a cis relationship at the ring junction. However, an almost identical substrate, save for a trans configuration between the C and D rings instead of the cis configuration, was prepared and served in further establishing the applicability of this methodology to the synthesis of Magellanine by successfully undergoing the 5-exo-dig/Prins reaction and generating the tetracyclic products. Studies of the steps following the key transformation were performed on the model substrate, allowing for the evaluation of these steps prior to their use in the synthesis. The results of the studies indicate a possible need to revisit the order in which the steps should be carried out. Promising solutions to the different obstacle encountered during the work are presented, demonstrating how the synthesis of Magellanine through a route featuring the 5-exo-dig/Prins cyclization is attainable.

This is a thesis in two parts. Part A examines two potential routes towards the synthesis of the communesin family of alkaloids, as well as an overview of some of the successful synthetic routes to date. Our first proposed route involves the gold catalyzed isomerization of an o-amino aryallene to a vinyl imine and subsequent (formal) cycloaddition with an indole. This would have allowed quick access to the pentacyclic core of the communesins; however, the unexpected 5-endo-dig product was exclusively obtained in good to excellent yields. The second route involves the use of a Meerwein- Eschenmoser Claisen rearrangement. This route was successful in affording the C, D, E and F rings of the communesin alkaloids, however future work is required for completion of the synthesis. Also discussed in these sections is an alternative endgame approach involving a novel Pictet-Spangler reaction to afford the G ring, and the possibility of an asymmetric variation to the proposed route. Part B examines the use of alkyl aluminum sesquichlorides in the catalysis of Diels-Alder cycloadditions of sterically hindered systems, a current obstacle in organic chemistry. Previously developed methods are discussed and preliminary results are presented. Ethyl aluminum sesquichloride is compared to other alkyl aluminum catalyst, and the effects of temperature, catalysts loading, choice of solvent, the use of additives, and the use of chiral oxazolidinones are reported and what these result can tell us about the mechanism of catalysis are discussed.

Las sales de oro se han convertido en uno de los catalizadores por excelencia en una gran variedad de transformaciones orgánicas mediante la activación selectiva de alquinos, alenos y alquenos. Parte del trabajo de esta tesis doctoral se ha centrado en el estudio de la naturaleza carbénica o carbocatiónica de los intermedios de reacción presentes en las cicloisomerizaciones de 1,5-eninos catalizadas por complejos de oro. De esta forma se han desarrollado distintas metodologías de ciclación dando lugar a diferentes productos tricíclicos a partir de oxo-1,5-eninos o 1,5-bencileninos. Además, se ha podido aplicar estas nuevas metodologías de ciclación en la síntesis de productos naturales como etapa clave de la misma. Por último, nuestro interés se ha centrado en el desarrollo de reacciones intermoleculares de gran utilizad química catalizadas por oro. Por ello hemos desarrollado la síntesis de fenoles substituidos a partir de diferentes acetilenos y furanos. / Gold salts and complexes are the most active catalysts for the activation of alkynes, allenes and alkenes. Part of this Doctoral Thesis is focused on the study of the carbenic or cationic character of the reaction intermediates presents in the cycloisomerizations of 1,5-enynes catalyzed by goldcomplexes. Different methodologies have been developed to synthesize different tryciclic products from oxo-1,5-enynes or 1,5-benzylenynes. Moreover, these methodologies were applied successfully as the key step in the synthesis of natural products. Finally, our interest was focused on the development of intermolecular gold-catalyzed reactions. Therefore, we have developed a general synthesis of trisubstituted phenols from alkynes and furans.

This is a thesis in two parts. Part A examines two potential routes towards the synthesis of the communesin family of alkaloids, as well as an overview of some of the successful synthetic routes to date. Our first proposed route involves the gold catalyzed isomerization of an o-amino aryallene to a vinyl imine and subsequent (formal) cycloaddition with an indole. This would have allowed quick access to the pentacyclic core of the communesins; however, the unexpected 5-endo-dig product was exclusively obtained in good to excellent yields. The second route involves the use of a Meerwein- Eschenmoser Claisen rearrangement. This route was successful in affording the C, D, E and F rings of the communesin alkaloids, however future work is required for completion of the synthesis. Also discussed in these sections is an alternative endgame approach involving a novel Pictet-Spangler reaction to afford the G ring, and the possibility of an asymmetric variation to the proposed route. Part B examines the use of alkyl aluminum sesquichlorides in the catalysis of Diels-Alder cycloadditions of sterically hindered systems, a current obstacle in organic chemistry. Previously developed methods are discussed and preliminary results are presented. Ethyl aluminum sesquichloride is compared to other alkyl aluminum catalyst, and the effects of temperature, catalysts loading, choice of solvent, the use of additives, and the use of chiral oxazolidinones are reported and what these result can tell us about the mechanism of catalysis are discussed.

No description available.

This report summarises the work done on monohydroxy aliphatic alcohol upgrading using Au/TiO2 catalysis. The catalysts were initially tested using a plug-flow CO oxidation reactor; complete conversion of a stream of CO flowing over the catalyst bed at a GHSV of approximately 79,500 hr-1 was typically achieved without any required external heating. TEM analysis showed that the freshly prepared catalyst does not contain detectable Aunano clusters, while the spent CO oxidation catalyst had clearly visible nanoparticles with an average size of approximately 1.6 nm. XRD analyses showed that the final pH to which the deposition-precipitation procedure was adjusted had a major role in determining the average nanocluster size. Alcohols were oxidised using the 1% Au/TiO2 catalyst in a plug-flow reactor, with the alcohol vapour being produced by sparging a blended stream of helium and oxygen (typically made up to a total flowrate of 100 ml min-1). The temperature of the alcohol could be adjusted, thereby controlling the vapour mole fraction of alcohol. For methanol oxidation, the primary reaction pathway across the entire range of studied feed compositions was combustion. The onset of combustion occurred dramatically, in the range of 140-160°C. For ethanol oxidation, acetaldehyde selectivity increases and overall conversion decreases as the oxygen content of the feed stream decreases. The kinetics of the catalysed ethanol oxidation showed a compensation effect, described by the equation ln(A) = 0.2032EA + 2.6102 (EA in kJ mol-1). Propanol oxidation demonstrated the highest selectivity towards a value added product (propanaldehyde), with propanaldehyde being formed in significant quantities. However, combustion was still favoured at high temperatures when large excesses oxygen were present. The thermokinetic data calculated for n-propanol oxidation did not exhibit the compensation effect observed in ethanol oxidation; the EA for this reaction was stable at approximately 38 kJ mol-1. In the anaerobic catalysed reactions of ethanol and n-propanol, an oily layer was collected above the water meniscus in a cold trap. This oil could potentially be formed via poly-aldol condensation reactions of the aldehydes produced during oxidation. Though other researchers suggest these condensation reactions typically end in a cyclic dehydration into aromatic compounds, electrospray mass spectrometry found no indication of such products. Control reactions performed using unloaded TiO2 and porous Au (obtained by in-situ reduction of Au2O3) produced different product distributions, all requiring substantially higher reaction temperatures. This suggests that there must be a synergistic effect between the Au and TiO2 substrate which facilitates reactions. Furthermore, the product distributions of the 1% Au/TiO2 catalysed reactions were significantly different from results published by other researchers performing similar oxidations on Au(111) single crystals, where substantially higher selectivity towards value-added products (formaldehyde, acetaldehyde, and propanaldehyde) is typically observed.

No description available.