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No description available.

It has been shown that $\eta\sp5$-cyclopentadienyl)dicarbonylcobalt is reactive to Friedel-Crafts' acylation with both organic and organometallic acid chlorides: acetyl, p-anisoyl, benzoyl, 2-naphthoyl, and p-toluoyl chlorides and ($\eta\sp5$-chloroformylcyclopentadienyl)($\eta \sp5$-cyclopentadienyl)iron, bis($\eta\sp5$-chloroformylcyclopentadienyl)iron, and ($\eta\sp5$-chloroformylcyclopentadienyl)-manganese tricarbonyl. However, ($\eta\sp5$-cyclopentadienyl)carbonyl(triphenylphosphine)cobalt is unreactive to Friedel-Crafts' acylation. Infrared and NMR studies of the acylation of ($\eta\sp5$-cyclopentadienyl)carbonyl(triphenyl-phosphine)cobalt indicate that this compound contains many reactive sites, with the cyclopentadienyl ring being the less favored. Analogous spectral studies of ($\eta\sp5$-cyclopentadienyl)dicarbonylcobalt support acylation of the cyclopentadienyl ring but also suggest other sites for reaction. All ketones derived from ($\eta\sp5$-cyclopentadienyl)dicarbonylcobalt have been reacted with triphenylphosphine and/or diphenylacetylene to give the phosphine and/or tetraphenylcyclobutadiene derivatives. Ketone derivatives of ($\eta\sp5$-cyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)cobalt have been shown to undergo typical organic reactions: lithium aluminum hydride/aluminum chloride reduction, sodium borohydride reduction, and the Wittig reaction. ($\eta\sp5$-Carbomethoxycyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)cobalt has been synthesized and used for the preparation of the following derivatives: ($\eta\sp5$-carboxycyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)-cobalt, ($\eta\sp5$-chloroformylcyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)-cobalt, ($\eta\sp5$-carbamoylcyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)cobalt, ($\eta\sp5$-cyanocyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)cobalt, and bis- (($\eta\sp5$-carboxycyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)cobalt) anhydride. The preparation of a pinacol from ($\eta\sp5$-benzoylcyclopentadienyl)-($\eta \sp4$-tetraphenylcyclobutadiene)cobalt has been attempted. Two products have been isolated. ($\eta\sp5$-Chloroformylcyclopentadienyl)($\eta \sp4$-tetraphenylcyclobutadiene)cobalt has been demonstrated to react with ferrocene to give the corresponding heterobimetallic compound. Other heterobimetallics have been prepared from ($\eta\sp5$-cyclopentadienyl)dicarbonylcobalt and ($\eta\sp5$-chloroformylcyclopentadienyl)($\eta \sp5$-cyclopentadienyl)iron, bis($\eta\sp5$-chloroformylcyclopentadienyl)iron, or ($\eta\sp5$-chloroformylcyclopentadienyl)manganese tricarbonyl.

Abstract The development of quinolones is described from the first quinolone to the latest fluoroquinolones. Quinolones have generated considerable interest since their discovery because of their antibacterial capabilities. Analogs incorporating the 4-quinolone ring system comprise a largely expanding group of synthetic compounds. The development of antibacterial resistance has created the need for an efficient synthesis of quinolones that can be easily adapted toward the assembly of quinolone based antibacterial drugs. There are several reported approaches to the 4-quinolone ring system. Many of these methods use expensive starting materials, require the removal of high boiling solvents, or use high temperature conditions (>200°C) for the final cyclization. Our synthesis of 4-quinolones was achieved via continuous flow chemistry using inexpensive starting materials in easily removable solvents, and under mild conditions. Flow chemistry is the use of technology that allows a continuous flow of reagents to be introduced at various points along a process stream, enabling interaction under highly controlled conditions. By employing this technology we achieved a more rapidly scalable synthesis of 4-quinolones, offering safer reacting conditions and highly reproducible results.

<p>This licentiate thesis is based on the development of catalytic reactions for the synthesis and application of organometallic reagents. By use of palladium pincer-complex catalysts, we have developed an efficient procedure for the synthesis of allylboronates starting from allylic alcohols. These reactions were further extended by including various one-pot multi-component reactions, using the in situ generated allylboronates. Furthermore, novel unsymmetrical palladium pincer-complexes were synthesized and studied in auto-tandem catalysis.</p>

This licentiate thesis is based on the development of catalytic reactions for the synthesis and application of organometallic reagents. By use of palladium pincer-complex catalysts, we have developed an efficient procedure for the synthesis of allylboronates starting from allylic alcohols. These reactions were further extended by including various one-pot multi-component reactions, using the in situ generated allylboronates. Furthermore, novel unsymmetrical palladium pincer-complexes were synthesized and studied in auto-tandem catalysis.

This thesis deals with the study of oxazoline-based ligands in metal-catalyzed asymmetric reactions. The first part describes the synthesis of six new bifunctinal pyridine-bis(oxazoline) ligands and their applications in asymmetric metal-catalysis. These ligands, in addition to a Lewis acid coordination site, are equipped with a Lewis basic part in the 4-position of the oxazoline rings. Dual activation by means of this system was probed in cyanide addition to aldehydes. The second part is concerned with the synthesis of two pyridine-bis(oxazoline) ligands bearing bulky triazole groups in the 4-position of the oxazoline rings and a macrocyclic ligand consisting of a pyridine-bis(oxazoline) moiety and a diaza-18-crown-6 ether. The synthesis of these compounds benefits from the use of “click chemistry”. The ligands thus obtained were tested in different asymmetric catalytic reactions. Complexation studies with different bifunctional molecules that could bind into the cavity of the macrocycle were carried out using NMR spectroscopy. A third chapter is devoted to the synthesis of a supported pyridine-bis(oxazoline) catalyst and its use in catalysis. The pyridine-bis(oxazoline) ligand was efficiently connected to a polystyrene resin via a robust triazole linker. This resin could be employed in different metal-catalyzed asymmetric reactions and good results were obtained in terms of yield and enantioselectivity. Moreover, this polymer-bound ligand could be easily and efficiently recycled. Finally, the last part deals with the use of a hydroxy-containing phosphinooxazoline ligand in the hydrosilylation of imines and in the asymmetric intermolecular Heck reaction. A cationic iridium complex of this ligand was studied by NMR spectroscopy. / QC 20100914

Life, as we know it, has emerged from the association of simple building blocks (e.g. HCN, NH3, aldehydes, etc). The reactions required to form the complex subunits of life face a great entropic barrier due to the intermolecular nature of their reactivity. Intermolecular reactions are slow at low concentrations, and therefore, the assembly of complex subunits requires the presence of a concentration mechanism. Formaldehyde, which was present in concentrations as high as 0.02 M, may have been used as a concentration mechanism on early Earth. By tethering two molecules together, formaldehyde allows catalysis via temporary intramolecularity. Moreover, formaldehyde has been shown to act as a hydrolase / hydratase mimic, allowing important rate accelerations in hydration and hydrolysis reactions which are of fundamental importance to prebiotic chemistry. Herein, the efficiency of formaldehyde as a catalyst, operating via temporary intramolecularity is demonstrated for a hydroamination reaction that occurs in dilute aqueous conditions. First, using soluble N-methylallylamine and Nmethylhydroxylamine, formaldehyde allowed catalytic turnover at prebiotically relevant formaldehyde concentrations (0.02 M) for a model hydroamination reaction. The efficiency of formaldehyde was compared to other prebiotic aldehydes, demonstrating that although other prebiotic aldehydes are capable of inducing temporary intramolecularity, they were inferior.A second small molecule which may have played a role in the origin of life is D-glyceraldehyde. Since life’s molecules are homochiral, there is a need to explain how this homochirality arose. There have been many breakthroughs by the scientific community when it comes to addressing this challenge, however there is still no general consensus on the origins of homochirality from a prebiotic perspective. Herein, we demonstrate that D-glyceraldehyde is capable of templating a challenging intermolecular reaction while also transmitting some of its chirality to the product. Though the enantiomeric excess produced was generally low (usually around 20 %), there is a significance behind these results due to prebiotically relevant amplification procedures. Lastly, formaldehyde is examined as a possible desymmetrizing agent; coupled with Brønsted acids, the possibility of formaldehyde to induce desymmetrization of alpha-amino or alpha-hydroxy diesters to produce azlactones, and oxalactones, respectively will be established. Moreover, the use of a chiral Brønsted acid would introduce the ability to achieve this transformation in an enantioselective manner. The resulting azlactones / oxalactones are valuable for two reasons: 1) the lactones are present in bioactive molecules, and 2) the lactones can be hydrolyzed to produce chiral alpha-amino / alpha-hydroxy acids. Therefore, we began a systematic study of the conditions required to allow this transformation to occur. This study indicates that the desymmetrization of an alpha-amino diester is possible, producing moderate yields of the resulting azlactone. The desymmetrization of alpha-hydroxy diesters however proved more challenging, and no conversion was observed. Further investigation is required to the increase efficiency of the desymmetrizations, and experimentation with chiral Brønsted acids is required in order to discover enantioselective transformations.

No description available.