Student Number : 9201775F - MSc dissertation - School of Chemistry - Faculty of Science / The base/light-induced cyclisation (condensation) reaction between alkyl and carbonyl substituents on biaryl compounds discovered in the University of the Witwatersrand laboratories was used to synthesise benzo[c]carbazoles. Specifically, 5,7-dimethyl-7H-benzo[c]carbazole was synthesised from 2-methyl-1H-indole in 79 % yield over four steps. The reaction sequence involved bromination of 2-methyl-1H-indole at C-3 to give 3-bromo-2-methyl-1H-indole. The subsequent methylation of the amino group to give 3-bromo-1,2-dimethyl-1H-indole was followed by Suzuki coupling with acetophenone-2-boronic acid under non-aqueous reaction conditions to give 1-[2-(1,2-dimethyl-1H-indol-3-yl)phenyl]. Lastly, tBuOK/hν–induced cyclisation of the product yielded the desired benzo[c]carbazole. 10-Methoxy-5,7-dimethyl-7H-benzo[c]carbazole was synthesized analogously in 75% yield from 5-methoxy-2-methyl-1H-indole.

Carbaryl toxicity, metabolism, and distribution in adults of three species of grass bugs _from the genus Labops were studied in relation to species, sex, and treatment with piperonyl butoxide. Lc50 values for 8 hour exposure periods ranged from 0.02-0.14, 0.03-0.3, and 0.2-0.7 μg carbaryl/vial for L. utahensis, L. hirtus, and L. hesperius respectively. The males were more susceptible to carbaryl than females. Males of L. utahensis were more susceptible than L. hirtus and L. hesperius respectively. The synergist difference values (Lc50 of carbaryl alone - Lc50 values of carbaryl after piperonyl butoxide treatment) were measured. The percent dependency of these _insects on MFOs for detoxifying carbaryl was estimated based on the theoretical synergist difference which was calculated by the equation Log LC50 = 1.014 log SD - 0.009. The percent dependency values were 38-59, 25-46, and 13-33% for L. hesperius, L. hirtus, and L. utahensis, respectively. Males of L. utahensis had the lowest percent dependency upon MFOs in detoxifying carbaryl (13%) indicating the possibility that carbaryl toxicity may be controlled by other potential defense mechanisms which are relatively ineffective themselves in view of the low tolerances of the insects to carbaryl. Treatment with piperonyl butoxide resulted in greater enhancement of carbaryl toxicity against L. hesperius (synergized Lc50 0.1-0.26 μg carbaryl/vial) while it showed a moderate effect on L. hirtus (synergized Lc50 0.02-0.16 μg carbaryl/vial). Piperonyl butoxide's effect was less pronounced in the case of L. utahensis (synergized Lc50 0.013- 0.09 μg carbaryl/vial. Unmetabolized carbaryl was the principle compound isolated from the bugs after 6 hours from treatment, being more prominent in males of L. hirtus (71.1% of the total metabolites) and less prominent in females hesperius (36.7% of the total metabolites). The mechanism of detoxication appeared to include ring hydroxylation for both species and sexes. 4 and 5-hydroxycarbaryl were the only metabolites associated with the degrading of carbaryl by the bugs, since the levels of metabolites obtained were too low for accurate quantitation. Pretreatment with piperonyl butoxide prevented the appearance of both carbaryl metabolites in the organosoluble fraction and increased the accumulation of unmetabolized carbaryl. This effect was probably due to inhibition of the insect's MFO system. Generally, this study showed a good correlation between the bioassays and the metabolic studies, thus reflecting the effectiveness of the bioassays along with synergist difference (SD) and percent dependency concepts in establishing some conclusions regarding the MFOs of Labops bugs. Further application of these techniques with agricultural insects should provide a practical means of characterizing field populations for insecticide tolerance, relative levels of MFOs and their role as a defense mechanism.

Il sinergizzante piperonil-butossido (PBO) usato in combinazione con insetticidi è in grado di contrastare i parassiti resistenti inibendo temporaneamente i sistemi di detossificazione. Nuovi sinergizzanti sono stati sintetizzati a partire dalla struttura molecolare del PBO, ma anche gli insetti utili come le api possono risentire di una maggiore efficacia degli insetticidi. In questo studio abbiamo osservato l’attività enzimatica in vitro (esterasi, acetilcolinesterasi, glutatione S-transferasi e monossigenasi P450) di api operaie Italiane e Carniche in presenza del PBO e dei suoi nuovi derivati del benzodiossolo e 2,3-diidrobenzofurano mediante saggi spettrofotometrici, per determinare se i sistemi di detossificazione e altri sistemi enzimatici sono influenzati dai sinergizzanti. I nuovi derivati del PBO possono inibire parzialmente le esterasi in alcune popolazioni di api più sensibili. Altri sistemi enzimatici non sembrano essere inibiti dai sinergizzanti studiati. Studi di tossicità acuta orale e di contatto sono stati condotti in laboratorio presso il Bee Research Institute (Dol, Repubblica Ceca) su api operaie Carniche per verificare il possibile incremento di tossicità degli insetticidi imidacloprid e alfa-cipermetrina in combinazione con PBO e i suoi derivati del benzodiossolo. Gli studi hanno mostrato una differenza significativa tra la tossicità dei due principi attivi da soli e in combinazione con i sinergizzanti. / The synergist piperonyl-butoxide (PBO) has been proved to successfully control resistant pests when combined with insecticides by temporarily inhibiting the detoxification systems which lead to resistance. New synergists, starting from the molecular structure of PBO, have been developed but pollinators may also suffer from an increased efficacy of insecticides. In this study we observed in vitro enzyme (esterases, acetylcholinesterases, glutathione S-transferases and P450 mixed function oxidases) activity of Italian and Carniolan honey bee workers in presence of the synergist PBO and its novel benzodioxole and 2,3-dihydrobenzofuran derivatives through spectrophotometric assays, to determine if detoxification systems and other enzymatic systems are affected by synergists. This data show that novel PBO derivatives may partially inhibit esterases in some honey bee populations which are more sensitive. Other enzymatic systems seem not to be targeted by the studied synergists. Acute oral and contact toxicity studies were conducted in laboratory conditions at the Bee Research Institute (Dol, Czech Republic) on adult Carniolan workers to investigate the possible increase of imidacloprid and alpha-cypermethrin toxicity when combined with PBO and its benzodioxole derivatives. Tests showed some significant difference between the toxicity of the two active principles alone and combined with the synergists.

The current study discusses the preparation and long-term performance of polymer composites used for various purposes under different ageing conditions. The first part deals with the preparation and characterization of polymer nanocomposites based on poly(ethylene-co-butyl acrylate) (EBA–13 and EBA–28 with 13 and 28 wt % butyl acrylate, respectively) and 2–12 wt % (0.5–3 vol %) of aluminum oxide nanoparticles (two types with different specific surface areas and different hydroxyl-group concentrations; uncoated and coated with, respectively, octyltriethoxysilane and aminopropyltriethoxysilane). The nanocomposite with EBA–13 showed better overall nanoparticle dispersion while EBA–28 resulted in poor dispersion, probably due to insufficiently high shear forces acting during extrusion mixing which were unable to break down nanoparticle agglomerates. The activity of hindered phenolic antioxidant (0.2 wt%) in all EBA nanocomposites was assessed by determining the oxidation induction time using DSC. The composites containing uncoated aluminium oxide nanoparticles showed a much shorter initial OIT than the pristine polymer with the same initial concentration of antioxidant, indicating adsorption of antioxidant onto the nanoparticle surfaces. Composites containing coated nanoparticles showed a significantly smaller decrease in the initial OIT, suggesting the replacement of hydroxyl groups with organic silane tails, decreasing the concentration of available adsorption sites on the nanoparticle surfaces. The decrease in OIT with increasing ageing time in dry air at 90 °C of the nanocomposites was slower than that of the unfilled pristine polymer, suggesting a slow release of antioxidant from adsorption sites. The EBA nanocomposites exposed to liquid water at 90°C showed faster decrease of OIT than samples exposed to dry or humid air. The migration rate of antioxidant was controlled by the boundary conditions in the case of ageing in humid air and liquid water. The antioxidant diffusivity was lower for the composites containing uncoated ND than for the composites containing ND coated with octyltriethoxysilane or aminopropyltriethoxysilane. The migration and chemical consumption of deltamethrin DM, (synthetic pyrethroid) and synergist piperonyl butoxide from molded polyethylene sheets was also studied. Deltamethrin and piperonyl butoxide are often used for food  storage and insect control purposes. DM showed no signs of crystallization and remained in a liquid state after being cooled to room temperature. Exposure of polyethylene compound sheets to liquid water (at 80 &amp; 95 °C), caused degradation and hydrolysis of the ester bond in the DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas in air at 80 °C (60 and 80 %RH) the loss of DM and PBO was negligible over 30 days. The long-term performance of medium-density polyethylene stabilized with six different phenolic antioxidants (0.1 wt%) in aqueous chlorinated media at 70 °C was studied. The results were compared with data for previously studied solutions of antioxidants in squalane (a liquid, low molar mass analogue of polyethylene). A linear relationship was established between the time to reach antioxidant depletion in polyethylene tape samples and the time in squalane samples. Infrared spectroscopy and scanning electron microscopy of drawn samples revealed the onset of surface oxidation and surface embrittlement in tape samples exposed beyond the time for antioxidant depletion. / <p>QC 20121109</p> / Cable insulation materials / Loss of deltamethrin and pipronyl butoxide from polyethylene / long-term performance of polyethylene in chlorine dioxide water

L’afide del pesco Myzus persicae rappresenta uno degli insetti più dannosi in agricoltura. Estremamente polifago e cosmopolita, viene combattuto principalmente con trattamenti insetticidi. Nel corso degli ultimi anni neonicotinoidi e piretroidi hanno rappresentato i componenti principali delle strategie di difesa contro questa specie, ma recenti programmi di monitoraggio condotti in Sud Europa hanno rivelato la presenza di popolazioni resistenti, mettendo in dubbio l’efficacia a lungo termine di queste classi di prodotti. Il presente lavoro prende in esame la diffusione dei principali meccanismi di resistenza agli insetticidi nelle popolazioni di M. persicae presenti sul territorio italiano. La prima parte si concentra sulle resistenze target-site e considera la distribuzione delle principali mutazioni che sono state associate alla resistenza a neonicotinoidi e piretroidi. La seconda parte riguarda le resistenze metaboliche e analizza le principali classi di enzimi associate ad attività di sequestro o detossificazione delle molecole di insetticida. Infine, il progetto si focalizza sulla caratterizzazione delle possibili interazioni tra tali enzimi detossificanti e molecole sinergizzanti quali il ben noto piperonil butossido (PBO). I risultati ottenuti consentiranno di migliorare le strategie di difesa per evitare trattamenti inefficaci e mantenere il più a lungo possibile l’efficacia dei prodotti oggi disponibili per il controllo di M. persicae. / The green peach aphid Myzus persicae is a globally significant crop pest, controlled mainly by chemical treatments. In recent years neonicotinoids and pyrethroids have been the main components of pest management strategies used by growers. However, recent monitoring programmes in Southern Europe have shown the widespread presence of resistant populations, posing a serious threat to the long-term efficacy of these insecticide classes. The present work aims to characterise the main biochemical and molecular mechanisms responsible for insecticide resistance in Italian populations of M. Persicae. The first part is focused on target-site resistance and consider the frequency and distribution of the main target-site mutations associated with neonicotinoid and pyrethroid resistance. The second part is related to metabolic resistance and analyses the involvement of detoxifying enzymes able to sequester or metabolise the insecticide molecules. Furthermore, the project aims to characterise possible interactions between those enzymes and synergistic compounds like the well-known piperonyl butoxide (PBO). Results obtained by this investigation will help to improve insecticide resistance management strategies, in order to avoid ineffective applications and maintain the long-term sustainability of chemical control against M. persicae.

The three insecticides of interest were lindane (an organochlorine), malathion (an organophosphate) and piperonyl butoxide (PBO; a synergist). Based on minimum cytotoxicity (> LC25), the following concentrations were chosen for the pesticide mixture studies: 70μM lindane (Lind), 50μM malathion (Mal) and 55μM PBO. In the AlamarBlue cytotoxicity assay, individual pesticide and mixtures of malathion/PBO (MP) and malathion/lindane (ML) prompted cytotoxicity with varying intensities (Mal 18.8%, Lind 20.4%, PBO 23.5%, ML 53.6% and MP 64.9%). Cytopathological analysis revealed apoptotic features in treated cells and the DNA Ladder Assay confirmed the presence of DNA fragments. The specific mode of cell death was examined via the 7-aminoactinomycin D (7-AAD) Staining Assay. Apoptosis was detected in each treatment (Mal 6.5%, Lind 12.0%, PBO 13.2%, ML 19.3% and MP 23.4%). Furthermore, 7-AAD staining in combination with fluorescent-labeled monoclonal antibodies, PE-CD45RB/220 and FITC-CD90, was performed. B-cells were more susceptible to Mal and PBO treatments than were T-cells. The pro-oxidant activity of the pesticides was monitored via the Dichlorofluorescin Diacetate assay. Exposure to pesticides for 15 minutes increased H2O2 production above the controls, Mal 21.1%; Lind 10.8%; PBO 25.9%; ML 26.8%; MP 37.8%. The activities of antioxidant enzymes, glutathione peroxidase (GSH-Px) and glutathione reductase (GR) were altered by these treatments. GR was significantly reduced for the pesticide mixtures only (control: 51.7; Mal: 48.2; Lind: 50; PBO: 52.3; ML: 40.5; MP: 42 Units/mg). GSH-Px activity was severely reduced for all the pesticide treatments (control: 44.9; Mal: 30.2; Lind: 30.6; PBO: 32.4; ML: 21.1; MP: 21.1 Units/mg). These results indicate that exposure to these pesticide and pesticide mixtures induces apoptosis and oxidative stress. / Master of Science

Cette thèse de doctorat porte sur la catalyse à partir de métaux de transition et sur la substitution homolytique aromatique favorisée par une base visant à former de nouvelles liaisons C–C, et à ainsi concevoir de nouvelles structures chimiques. Au cours des vingt dernières années, des nombreux efforts ont été réalisés afin de développer des méthodologies pour la fonctionnalisation de liens C–H, qui soient efficaces et sélectives, et ce à faible coût et en produisant le minimum de déchets. Le chapitre d'introduction donnera un aperçu de la fonctionnalisation directe de liens C–H sur des centres sp2 et sp3. Il sera également discuté dans cette partie de certains aspects de la chimie radicalaire reliés a ce sujet. Les travaux sur la fonctionnalisation d’imidazo[1,5-a]pyridines catalysée par des compleces de ruthénium seront présentés dans le chapitre 2. Malgré l'intérêt des imidazo[1,5-a]azines en chimie médicinale, ces composés n’ont reçu que peu d'attention dans le domaine de la fonctionnalisation de liens C–H. L'étendue de la réaction et l'influence des effets stériques et électroniques seront détaillés. Les cyclopropanes représentent les 10ème cycles carbonés les plus rencontrés dans les petites molécules d’intérêt pharmacologique. Ce sont aussi des intermédiaires de synthèse de choix pour la création de complexité chimique. Malgré de grands progrès dans le domaine de la fonctionnalisation de liens C(sp3)–H, l'étude des cyclopropanes comme substrats dans les transformations directes est relativement nouvelle. Le chapitre trois présentera l'arylation intramoléculaire directe de cyclopropanes. Cette réaction est réalisée en présence de palladium, en quantité catalytique, en combinaison avec des sels d’argent. Des études mécanistiques ont réfuté la formation d'un énolate de palladium et suggéreraient plutôt une étape de métallation - déprotonation concertée. En outre, les cycles de type benzoazepinone à sept chaînons ont été synthétisés par l'intermédiaire d'une séquence d'activation de cyclopropane/ouverture/cyclisation. Une arylation directe intermoléculaire des cyclopropanes a été réalisée en présence d'un auxiliaire de type picolinamide (Chapitre 4). Les deux derniers chapitres de ce mémoire de thèse décriront nos études sur la substitution homolytique aromatique favorisée par une base. Le mécanisme de la réaction de cyclisation intramoléculaire d'halogénures d'aryle, réalisée en présence de tert-butylate de potassium, a été élucidé et se produit via une voie radicalaire (Chapitre 5). La transformation, exempte de métaux de transition, ne nécessite que la présence d’une base et de pyridine comme solvant. Cette réaction radicalaire a été étendue à la cyclisation d'iodures d'alkyle non activés en présence d'un catalyseur à base de nickel et de bis(trimethylsilyl)amidure de sodium comme base (Chapitre 6). Des études de RMN DOSY ont démontré une association entre le catalyseur, la base et le matériel de départ. / The dissertation will focus on transition metal catalysis and base-promoted homolytic aromatic substitution as a means of forming new C–C bonds, and thus designing new chemical scaffolds. During the last twenty years, tremenduous efforts have been expended to achieve low-cost, waste-free, efficient and selective C–H bond functionalization methodologies. The introductory chapter will provide an overview of direct functionalization of C–H sp2 and sp3 centers, as well as discuss relevant topics in radical chemistry. Work on the ruthenium-catalyzed functionalization of imidazo[1,5-a]pyridines will be presented in Chapter 2. Despite interest from the medicinal chemistry field, imidazo[1,5-a]azines have received little attention in the C–H functionalization field. The scope of the reaction and, in particular, the influence of sterics and electronics will be detailed. Cyclopropanes represent the 10th most encountered rings in small drug synthesis. They are also valuable synthetic intermediates en route to more chemical complexity. Despite great advances in the field of C(sp3)–H functionalizations, the exploration of cyclopropanes as substrates in direct transformations is relatively novel. Chapter three will present the intramolecular direct arylation of cyclopropanes. A combination of palladium catalysis in presence of a silver salt was found to mediate the reaction. Mechanistic studies disproved the formation of a palladium-enolate and pointed towards a concerted metalation-deprotonation pathway. Furthermore, seven-membered benzoazepinone rings were synthesized via a cyclopropane activation/opening/cyclization sequence. An intermolecular direct arylation of cyclopropanes was achieved in presence of a picolinamide auxiliary (Chapter 4). The last two chapters of the thesis will describe our studies on base-promoted homolytic aromatic substitution. A potassium tert-butoxide-promoted intramolecular cyclization of aryl halides was shown to occur through a radical pathway (Chapter 5). The transition metal-free transformation occurred in the sole presence of the base and pyridine as the solvent. The radical process was extended to the cyclization of unactivated alkyl iodides in presence of a nickel catalyst and sodium hexamethyldisilzide as the base (Chapter 6). DOSY NMR studies demonstrated an association between the catalyst, base and starting material.

No description available.