M. Tech. (Department of Chemistry, Faculty of Applied and Computer Science), Vaal University of Technology / Cadmium and cobalt complexes of urea and thiourea were synthesized using ethanol as a solvent. All complexes were refluxed at 70 - 80 °C, left to cool at room temperature, washed with methanol and acetone to remove impurities and dried at an open environment. The characterization of complexes was done using FTIR spectroscopy, elemental analysis and TGA. The complexes were found to coordination with the ligands through sulphur and oxygen atoms to the metal, instead of nitrogen. These were as results of wavelength shifting from high to low frequency from spectra of the complexes as compare to their free ligands. These observations make these complexes good candidates for the possible use in synthesis of metal sulphides or oxides nanoparticles. Thermogravimetric analyses of all the complexes were conducted to check the stability of use as precursors for nanoparticles at low and high temperature. A number of thiourea and urea complexes with cadmium and cobalt have been prepared and used in the preparation of metal sulphides/oxides nanoparticles. Complexes start to decompose at low temperature about 100°C and the last decomposition step was at about 800-900°C, which is convenient to thermal decomposition of precursors in the high boiling solvents or capping agent to prepare surface capped metal sulphides/oxides nanoparticles. The complexes were easy to synthesize, low cost and stable in air and were obtained in reasonable yields. All the complexes reported in this study have been used as single source molecular precursor in the preparation of cadmium oxide, cadmium sulphide, cobalt oxide, cobalt sulphide nanoparticles (normal) and as mixture of any two complexes to form core-shells nanoparticles. Quality nanoparticles synthesis requires three components: precursors, organic surfactants and solvents. The synthesis of the nanoparticles can be thought of as a nucleation event, followed by a subsequent growth period. Both the nucleation and growth rates were found to be dependent upon factors such as temperature, growth time, and precursor concentration. For a continuous flow system the residence time (at nucleation and growth conditions) was also found to be important. In order to separate the nucleation and growth events, injection techniques were employed to achieve rapid nucleation of nanoparticles with final size dictated by the growth temperature and/or residence time through the growth zone of the reaction system. Good crystalline normal nanoparticles were obtained from thermolysis of the precursors in hexadecylamine (HDA) as the capping agent at fixed concentrations, temperature and time. All nanoparticles showed a blue-shift in band edges with good photoluminescence behaviour which is red-shifted from their respective band edges and XRD patterns, the crystal structure are in hexagonal phase. The particles showed rods, spheres and hexagonal shapes. Nucleation and growth mechanism brings new avenue in nanostructures called core-shells, which have been reported to have improved luminescence, quantum yields, decreased fluorescence lifetimes, and benefits related to the tailoring of the relative band-gap positions between the two materials. In this study cadmium and cobalt complexes of urea and thiourea were separately dispersed in TOP and injected separately (allowing nucleation/core to occur, followed by the shell) in hot HDA at 180ºC for 1hour to yield core-shell nanoparticles. Parameters, such as concentration, temperature and capping molecule as factor affecting nucleation and growth of the core-shells were monitored. The core-shell nanoparticles were characterized by UV/Vis spectroscopy, XRD and TEM. We observed spherical, tripod, bipods, hexagonal and irregular shaped nanoparticle as the concentration of the precursors was increasing, however we were able to form core-shells nanoparticles in one set of experiment 1:3 CdS-CdO, which are assumed to be a reverse type I coreshells nanoparticles. Exciton absorption peaks at higher energy than the fundamental absorption edge of bulk indicate quantum confinement effect in nanoparticles as a consequence of their small size. XRD patterns, crystals range from hexagonal, cubic and mixture of hexagonal and orthorhombic. A low temperature studies were also conducted a mixture of hexagonal and sphererical shapes with sheets like onion morphology were observed. / NRF HUB & SPOKES (VUT)

Etilenotiouréia (ETU) é uma substância tóxica, formada pela degradação e/ou biotransformação dos fungicidas etilenobisditiocarbamatos (EBDC). Seus resíduos podem ser encontrados em plantas e no ambiente, após o uso de EBDC na agricultura, ou em animais e no ser humano, quando expostos a esses produtos. Comprovadamente, a ETU tem a capacidade de induzir tumor na tireóide de roedores e no fígado de camundongo, apresentando evidência suficiente para carcinogenicidade em animais e evidência inadequada para carcinogenicidade em seres humanos. Os objetivos deste estudo foram: validar método analítico para determinação de resíduos de ETU nas matrizes estudadas; verificar a presença de resíduos de ETU em amostras de frutas (mamão, maçã e morango), coletadas em diferentes pontos de comercialização da cidade de São Paulo; avaliar os resultados e a contribuição de risco à saúde da população consumidora. Foram analisadas 90 amostras, sendo 30 de cada fruta (maçã, mamão e morango), adquiridas em diferentes pontos de comercialização da cidade São Paulo, no período de dezembro de 2005 a dezembro de 2006, distribuídas nas diferentes regiões do referido município e durante as estações do ano. Os parâmetros de validação avaliados foram: seletividade, linearidade, limite de quantificação, limite de detecção, exatidão e precisão. Os estudos de recuperação foram realizados com fortificações em três níveis (1, 2 e 10 LQ) em amostras controle. A determinação de resíduos de ETU foi feita por cromatografia a líquido de alto desempenho, com detector de absorção no ultravioleta (HPLC-UV) e cromatografia a líquido acoplada à espectrometria de massas em tandem (LC/MS/MS). Como todos os resultados obtidos por HPLC-UV apresentaram níveis de ETU abaixo do LQ limite de quantificação (10,0?g/kg), as quantificações foram realizadas no LC/MS/MS, com limite de quantificação e de detecção respectivamente de 1,0?g/kg e 0,5?g/kg. O método por LC/MS/MS mostrouse adequado para análise de ETU nos níveis de até 2,0?g/kg para maçã e morango e de até 10,0 ?g/kg para mamão, com recuperações médias de 75 a 110% e coeficientes de variação de 6 a 17%. Foram encontrados resíduos de ETU em 10 (33%) das amostras de maçã, em níveis que variaram de 1,0 a 3,7 ?g/kg (ppb); em 20 (67%) das amostras de mamão, de 1,0 a 5, 3?g/kg; em 2 (7%) das amostras de morango, de 1,0 a 1,4 ?g/kg. Estes valores estão abaixo do limite de 50?g/kg, estabelecido na União Européia. A estimativa da ingestão de resíduos de ETU pelo consumo das frutas estudadas, considerando o maior nível encontrado nesta pesquisa e dados fornecidos pelo IBGE, representam respectivamente 0,05 e 0,20 % da IDA (Ingestão Diária Aceitável, estabelecida pelo Codex Alimentarius), para a população em geral e crianças. A estimativa da ingestão de resíduos de EBDC pelo consumo dos alimentos (maçã, tomate, mamão, alface, morango, banana, laranja, cenoura), monitorados pelo PARA no período de 2001 a 2004, considerando os maiores níveis encontrados e 100% dos resíduos de ditiocarbamatos (CS2) como sendo originários do uso de EBDC, foi de 7,2% para a população em geral e de 28,9 % para crianças. Dados de ETU e EBDC em outros alimentos, incluindo os industrializados, em água de consumo e em amostras ambientais, além de dados mais refinados de consumo alimentar para subgrupos mais sensíveis (como crianças e mulheres grávidas), são necessários para se avaliar o risco de maneira mais global e condizente com a realidade, em prol da Saúde Pública. / Ethylene thiourea (ETU) is a toxic substance generated by the degradation and/or biotransformation of ethylenebisdithiocarbamates (EBDC) fungicides. Their residues may be found in plants and in the environment after EBDC's use in agriculture or in animals and humans when exposed to such products. ETU is confirmedly able to induce tumors in rodents' thyroids and in mouse's liver, showing enough evidence of carcinogenicity in animals and inadequate evidence of carcinogenicity in humans. The aims of this study were validating an analytical method for determining ETU residues in the studied sources, verifying the presence of ETU residues in fruit samples (papaya, apple and strawberry) collected from different commercial centers in the city of São Paulo; evaluating the results and their contribution as a risk to the consumers' health. Ninety fruit samples (30 samples of each fruit - papaya, apple and strawberry) were analyzed. The samples were purchased at different commercial centers in different regions of the city of São Paulo and over all seasons during December 2005 through December 2006. The validation parameters used were selectivity, linearity, accuracy and precision. Recovery studies were carried out with fortifications in 3 levels (1, 2 and 10 times the Limit of Quantification, LQ) in control samples. The determination of ETU residues was carried out by high performance liquid chromatography, ultra-violet absorption detector (HPLC/UV) and liquid chromatography coupled on tandem mass spectrophotometry (LC/MS/MS). Since all results obtained through HPLC/UV showed levels of ETU below the LQ (10.0 ?g/kg), quantification were carried out through LC/MS/MS with quantification and detection limits of 1.0?g/kg and 0.5 ?g/kg, respectively. The LC/MS/MS method proved adequate for analyzing quantities of ETU as low as 2.0 ?g/kg in apple and strawberry and 10.0 ?g/kg in papaya, with average recovery of 75 to 110 % and variation coefficients of 6 to 17 %. ETU residues were found in 10 (33%) apple samples with levels ranging from 1.0 to 3.7 ?g/kg (ppb); in 20 (67%) of papaya samples with levels ranging from 1.0 to 5.3 ?g/kg (ppb); and in 2 (7%) strawberry samples with levels ranging from 1.0 to 1.4 ?g/kg (ppb). These values are below the limit established in European Community (50 ?g/kg). The assessment of ETU intake, considering the consumption informed by IBGE (Instituto Brasileiro de Geografia e Estatística, the Brazilian Institute for Geography and Statistics) and the highest level observed in total fruit samples in this research, represent 0.05 % and 0.20 % ADI (Acceptable Daily Intake, established by the Codex Alimentarius) for geral population and children, respectively. The assessment of EBDC intake, considering the consumption informed by IBGE (Instituto Brasileiro de Geografia e Estatística, the Brazilian Institute for Geography and Statistics) and the highest level observed in food samples (apple, tomato, papaya, lettuce, strawberry, banana, orange, carrot), monitoring from 2001 through 2004 year in the PARA (Programa de Análise de Resíduos de Agrotóxicos em Alimentos, Program Monitoring of Pesticide Residues in Food, Brazil), and that 100% of dithiocarbamate (CS2) residues from EBDC's use, represent 7.2% and 28.9% ADI for geral population and children, respectively. ETU and EBDC data in other foods (including industrialized foods), water and environment samples, together with more refined food consumption data considering more sensitive population subgroups (as children and pregnants) are necessary to evaluate the risk in a more global and realistic way in favor of Public Health.

Etilenotiouréia (ETU) é uma substância tóxica, formada pela degradação e/ou biotransformação dos fungicidas etilenobisditiocarbamatos (EBDC). Seus resíduos podem ser encontrados em plantas e no ambiente, após o uso de EBDC na agricultura, ou em animais e no ser humano, quando expostos a esses produtos. Comprovadamente, a ETU tem a capacidade de induzir tumor na tireóide de roedores e no fígado de camundongo, apresentando evidência suficiente para carcinogenicidade em animais e evidência inadequada para carcinogenicidade em seres humanos. Os objetivos deste estudo foram: validar método analítico para determinação de resíduos de ETU nas matrizes estudadas; verificar a presença de resíduos de ETU em amostras de frutas (mamão, maçã e morango), coletadas em diferentes pontos de comercialização da cidade de São Paulo; avaliar os resultados e a contribuição de risco à saúde da população consumidora. Foram analisadas 90 amostras, sendo 30 de cada fruta (maçã, mamão e morango), adquiridas em diferentes pontos de comercialização da cidade São Paulo, no período de dezembro de 2005 a dezembro de 2006, distribuídas nas diferentes regiões do referido município e durante as estações do ano. Os parâmetros de validação avaliados foram: seletividade, linearidade, limite de quantificação, limite de detecção, exatidão e precisão. Os estudos de recuperação foram realizados com fortificações em três níveis (1, 2 e 10 LQ) em amostras controle. A determinação de resíduos de ETU foi feita por cromatografia a líquido de alto desempenho, com detector de absorção no ultravioleta (HPLC-UV) e cromatografia a líquido acoplada à espectrometria de massas em tandem (LC/MS/MS). Como todos os resultados obtidos por HPLC-UV apresentaram níveis de ETU abaixo do LQ limite de quantificação (10,0?g/kg), as quantificações foram realizadas no LC/MS/MS, com limite de quantificação e de detecção respectivamente de 1,0?g/kg e 0,5?g/kg. O método por LC/MS/MS mostrouse adequado para análise de ETU nos níveis de até 2,0?g/kg para maçã e morango e de até 10,0 ?g/kg para mamão, com recuperações médias de 75 a 110% e coeficientes de variação de 6 a 17%. Foram encontrados resíduos de ETU em 10 (33%) das amostras de maçã, em níveis que variaram de 1,0 a 3,7 ?g/kg (ppb); em 20 (67%) das amostras de mamão, de 1,0 a 5, 3?g/kg; em 2 (7%) das amostras de morango, de 1,0 a 1,4 ?g/kg. Estes valores estão abaixo do limite de 50?g/kg, estabelecido na União Européia. A estimativa da ingestão de resíduos de ETU pelo consumo das frutas estudadas, considerando o maior nível encontrado nesta pesquisa e dados fornecidos pelo IBGE, representam respectivamente 0,05 e 0,20 % da IDA (Ingestão Diária Aceitável, estabelecida pelo Codex Alimentarius), para a população em geral e crianças. A estimativa da ingestão de resíduos de EBDC pelo consumo dos alimentos (maçã, tomate, mamão, alface, morango, banana, laranja, cenoura), monitorados pelo PARA no período de 2001 a 2004, considerando os maiores níveis encontrados e 100% dos resíduos de ditiocarbamatos (CS2) como sendo originários do uso de EBDC, foi de 7,2% para a população em geral e de 28,9 % para crianças. Dados de ETU e EBDC em outros alimentos, incluindo os industrializados, em água de consumo e em amostras ambientais, além de dados mais refinados de consumo alimentar para subgrupos mais sensíveis (como crianças e mulheres grávidas), são necessários para se avaliar o risco de maneira mais global e condizente com a realidade, em prol da Saúde Pública. / Ethylene thiourea (ETU) is a toxic substance generated by the degradation and/or biotransformation of ethylenebisdithiocarbamates (EBDC) fungicides. Their residues may be found in plants and in the environment after EBDC's use in agriculture or in animals and humans when exposed to such products. ETU is confirmedly able to induce tumors in rodents' thyroids and in mouse's liver, showing enough evidence of carcinogenicity in animals and inadequate evidence of carcinogenicity in humans. The aims of this study were validating an analytical method for determining ETU residues in the studied sources, verifying the presence of ETU residues in fruit samples (papaya, apple and strawberry) collected from different commercial centers in the city of São Paulo; evaluating the results and their contribution as a risk to the consumers' health. Ninety fruit samples (30 samples of each fruit - papaya, apple and strawberry) were analyzed. The samples were purchased at different commercial centers in different regions of the city of São Paulo and over all seasons during December 2005 through December 2006. The validation parameters used were selectivity, linearity, accuracy and precision. Recovery studies were carried out with fortifications in 3 levels (1, 2 and 10 times the Limit of Quantification, LQ) in control samples. The determination of ETU residues was carried out by high performance liquid chromatography, ultra-violet absorption detector (HPLC/UV) and liquid chromatography coupled on tandem mass spectrophotometry (LC/MS/MS). Since all results obtained through HPLC/UV showed levels of ETU below the LQ (10.0 ?g/kg), quantification were carried out through LC/MS/MS with quantification and detection limits of 1.0?g/kg and 0.5 ?g/kg, respectively. The LC/MS/MS method proved adequate for analyzing quantities of ETU as low as 2.0 ?g/kg in apple and strawberry and 10.0 ?g/kg in papaya, with average recovery of 75 to 110 % and variation coefficients of 6 to 17 %. ETU residues were found in 10 (33%) apple samples with levels ranging from 1.0 to 3.7 ?g/kg (ppb); in 20 (67%) of papaya samples with levels ranging from 1.0 to 5.3 ?g/kg (ppb); and in 2 (7%) strawberry samples with levels ranging from 1.0 to 1.4 ?g/kg (ppb). These values are below the limit established in European Community (50 ?g/kg). The assessment of ETU intake, considering the consumption informed by IBGE (Instituto Brasileiro de Geografia e Estatística, the Brazilian Institute for Geography and Statistics) and the highest level observed in total fruit samples in this research, represent 0.05 % and 0.20 % ADI (Acceptable Daily Intake, established by the Codex Alimentarius) for geral population and children, respectively. The assessment of EBDC intake, considering the consumption informed by IBGE (Instituto Brasileiro de Geografia e Estatística, the Brazilian Institute for Geography and Statistics) and the highest level observed in food samples (apple, tomato, papaya, lettuce, strawberry, banana, orange, carrot), monitoring from 2001 through 2004 year in the PARA (Programa de Análise de Resíduos de Agrotóxicos em Alimentos, Program Monitoring of Pesticide Residues in Food, Brazil), and that 100% of dithiocarbamate (CS2) residues from EBDC's use, represent 7.2% and 28.9% ADI for geral population and children, respectively. ETU and EBDC data in other foods (including industrialized foods), water and environment samples, together with more refined food consumption data considering more sensitive population subgroups (as children and pregnants) are necessary to evaluate the risk in a more global and realistic way in favor of Public Health.

Carbene ligands over these years have become a heavily utilizes and effective ligand for catalysis. The diamino carbene class of ligands are slightly less understood. The effects of bis(carbene) ligand structures of palladium (II) catalysts were investigated using the ETS-NOCV method. The results showed that the amount of π-backbonding played a major role in the rate of the reaction for these NHC complexes. The amount of pi acceptance from the ligand increased in correlation to the length of the methylene linkage in the ligand back bone resulting in increased catalytic activity. The ETS-NOCV method was used to determine the deformation densities that had a contribution to this interaction based on visual interpretation. The percent contribution of pi interactions provided a linear correlation to the natural log of the initial reaction rate, indicating that π-backbonding plays a crucial role in the overall catalytic activity of the palladium complexes. Gold (I) bis acyclic diamino carbenes (ADCs) were investigated for the possibility to be strong hydrogen bond catalysts. The ligand motif of the gold (I) bisADCs were found to be analogous thiourea compounds. Based on NBO analysis there were some improvements to hydrogen bond donicity in comparison to thioureas with the same functional group. The complexes were analyzed for hydrogen bond interactions and polarizations interactions between simple nitroolefin substrate and the catalyst using ETS-NOCV. Results showed that the compounds can form a stable hydrogen bonding system and activate the substrate. This capability is tunable by changing the electron withdrawing properties of the ligase motif, providing the idea that gold (I) bisADCs have potential to be good hydrogen bond catalysts. New thiourea-like gold (I) catalysts utilizing the acyclic diamino carbene motif that were hypothesized were synthesized using a one pot synthesis approach utilizing a metal templated synthesis method. The synthesis, characterization, and application prove these complexes with their cationic centers and bisADCs ligand motif can be utilized for Friedel-Crafts alkylation of indoles, resulting in the production of three new compounds to literature. This research also provided a new application for this specific ligand class and further proved the robustness of ADC ligands.

Le squelette 1,3,5-triazépane-2,6-dione est un hétérocycle à sept chainons dérivé de dipeptides et accessible en quatre étapes en solution. Une voie de synthèse en parallèle sur support solide de cet hétérocycle a été élaborée. Cette synthèse, qui repose sur les principes de "catch and release" et de cyclo-clivage, a permis la création d’une chimiothèque de plus d’une centaine de composés. Pour augmenter la diversité du squelette 1,3,5-triazépane-2,6-dione, des modifications post-cyclisation peuvent avoir lieu telles que des réactions de N-mono-alkylation ou de N,N-di-alkylation de l’urée, des réactions d’acylation ou bien des réactions de thionation des fonctions carbonyles. De même, la synthèse des cycles analogues aux 1,3,5-triazépane-2,6-diones des tailles plus importantes a été examinée conduisant à l’obtention de plusieurs macrocycles.Les 1,3,5-triazépane-2,6-diones présentent un fort potentiel pour la recherche de molécules d’intérêt thérapeutique puisque le cycle est rigide, non-planaire et possède une bonne capacité de distribution des pharmacophores dans l’espace. Des molécules de cette famille présentent une activité inhibitrice modérée mais spécifique sur les phospholipases A2 secrétées humaines de type V et X. La recherche de nouveaux inhibiteurs de sPLA2 par une étude de relation structure/activité, par création d’une pince à calcium ou par simulation moléculaire a conduit à l’identification de nouveaux composés actifs. / The 1,3,5-triazepane-2,6-dione scaffold is a seven membered heterocycle derived from dipeptides and accessible in a four steps synthesis in solution. A parallel solid phase synthesis of this heterocycle was developed. This strategy, based on "catch and release" and cyclo-cleavage processes, had created a library containing more than one hundred compounds. To increase the diversity of 1,3,5-triazepane-2,6-dione moieties, some post-cyclisation modifications were performed, e.g. urea N-mono-alkylation or N,N-di-alkylation, acylation, and carbonyl thionation. Synthesis of larger cycles was also investigated and several macrocycles were obtained.The 1,3,5-triazepane-2,6-diones have a strong pharmacological interest, because their cycle is rigid, non-planar and can allow multiple presentation of pharmacophores in space. Some 1,3,5-triazepane-2,6-diones have shown a small but specific activity on the groups V and X of the human secreted phospholipases A2. Structure/activity relationships, clamp synthesis to bind calcium or virtual screening were the strategies used to identify new active compounds.

O presente trabalho visou o estudo da modificação química da celulose de linter (obtida de fonte de rápido crescimento e considerada a celulose de maior pureza isolada de fontes vegetais) através da sua derivatização em meio homogêneo, buscando-se a obtenção de materiais com características bem definidas e via um método que apresente boa reprodutibilidade. Dentre os derivados de celulose, os acetatos têm importância industrial significativa. No presente trabalho, acetatos de celulose obtidos no sistema de solvente cloreto de lítio/dimetilacetamida (LiCl/DMAc), com diferentes graus de substituição (GS) foram caracterizados através de 1H NMR, espectroscopia na região do infravermelho, viscosimetria e análises térmicas (DSC e TG). Através de métodos quantitativos aplicados às curvas termogravimétricas pode-se obter parâmetros cinéticos relacionados à decomposição térmica como a energia de ativação (Ea). Os resultados para os acetatos mostraram que conforme o GS aumenta, aumenta o grau de substituição de C2 e C3, e observa-se também aumenta Ea. Acetatos de celulose com diferentes GS foram utilizados para a obtenção de filmes a partir do mesmo sistema de solvente. Visando à obtenção de biocompósitos, filmes de acetatos de celulose com diferentes porcentagens de celulose foram preparados. Nestes filmes, os acetatos são considerados como matriz e a celulose como reforço, se tendo como pressuposto que as cadeias de celulose formarão agregados em solução, os quais serão mantidos nos filmes, atuando então como reforço. Este pressuposto é baseado em resultados de trabalhos anteriores, assim como estudos reológicos feitos no presente trabalho, que mostram que as cadeias de celulose se agregam, mesmo a baixas concentrações. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), cromatografia de exclusão por tamanho (SEC), microscopia eletrônica de varredura (MEV), solvatocromismo, dentre outras. A eliminação dos solventes após a obtenção dos filmes é um fator importante a ser considerado, e os resultados mostraram que o processo escolhido não leva a presença residual dos solventes utilizados. As imagens de MEV indicaram que fibras de celulose nos filmes de biocompósitos no geral não são visíveis em escala microscópica. Este resultado é promissor, pois sugere que as fibras de celulose podem estar presentes em escala nanométrica, já que para alguns filmes a ação como reforço foi observada, através da melhora em algumas propriedades. Ainda, a rugosidade dos filmes de biocompósitos foi alterada com a presença de celulose conforme mostram os resultados de AFM. Os resultados de DMTA indicaram que uma baixa porcentagem de celulose (5% de celulose) no filme de acetato de celulose com GS 0,8, foi suficiente para a ação como reforço ser observada, sugerindo que cadeias de celulose interagiram preferencialmente entre si, gerando estruturas supramoleculares de cadeias agregadas quando ainda no meio solvente (LiCl/DMAc), as quais permaneceram na preparação dos filmes. No entanto, para o filme obtido a partir de um GS maior (GS 1,5), o efeito de reforço da celulose nos filmes de biocompósitos ocorre apenas para a maior proporção de celulose (15% de celulose). Os resultados de ensaio à tração mostraram que dependendo da aplicação, ou seja, a necessidade de filmes mais resistentes à tração e maior rigidez, estes podem ser empregados. Adicionalmente, filmes de celulose e quitosana foram preparados no sistema de solvente NaOHaq./tiouréia. Nestes filmes, considera-se a quitosana como matriz e a celulose como agente de reforço. Acredita-se que as cadeias de celulose prefiram interagir entre si, gerando \"domínios\" de cadeias de celulose. Por este motivo, o termo biocompósito foi empregado também para estes filmes. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), biodegradação, sorção de umidade, microscopia de força atômica (AFM), dentre outras. Os resultados de difração de raios X mostram que o sistema de solvente não altera significativamente a cristalinidade dos filmes, comparativamente aos materiais de partida. As análises térmicas empregadas (TG e DSC) mostraram que a estabilidade térmica é alterada devido a presença dos dois polissacarídeos nos filmes de biocompósitos. O estudo de biodegradação dos filmes de biocompósitos em solo simulado mostrou que a velocidade de biodegradação está relacionada à proporção das regiões não cristalinas, que são mais acessíveis à água e aos microrganismos, isto é, quanto maior o valor de índice de cristalinidade, menor será a velocidade de biodegradação. Importante ressaltar que o comportamento destes filmes em relação à biodegradação está também relacionado com a morfologia apresentada pelos filmes. A análise de AFM mostrou que o aumento da proporção de quitosana nos filmes de biocompósitos leva a maiores valores de rugosidade. Os resultados obtidos para os filmes de quitosana, celulose e biocompósitos (quitosana/celulose), assim como para os filmes de acetato de celulose, celulose e biocompósitos (acetato de celulose/celulose) se mostraram promissores. / This work was aimed at studying the chemical modification of linters cellulose extracted from a source of rapid growth and considered the most pure cellulose from vegetable sources. Derivatization was carried out in a homogeneous medium to obtain materials with well-defined properties via a reproducible method. Here cellulose acetate was obtained with various degrees of substitution (DS) using the lithium chloride/dimethylacetamide system (LiCl/DMAc), being characterized with 1H NMR, infrared spectroscopy, viscometry measurements and thermal analysis (DSC and TG). The thermogravimetric curves were analyzed quantitatively, which allowed the determination of kinetics parameters for the thermal decomposition, including the activation energy (Ea). Ea and the substitution at C2 and C3 increased with increasing DS. Cellulose acetates with distinct DS were obtained in the form of films using the solvents mentioned above. Furthermore, biocomposite films were prepared with different contents of cellulose, in which the acetates were considered as matrices and the cellulose was the loading material. It is assumed that the cellulose chains form aggregates in solution, which will be preserved in the films, thus acting as reinforcement. This hypothesis was based on previous work and confirmed here with rheological data. We show that the cellulose chains are aggregated even at low concentrations. These films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), size exclusion chromatography (SEC), atomic force microscopy (AFM) and scanning electron microscopy. No residual solvent was present after film preparation. The SEM images indicated that the cellulose fibers in the biocomposite films are not visible at the microscopy scale, thus suggesting the presence of cellulose nanofibers. This is promising due to the possible enhancement in the mechanical properties, which was actually observed with a threshold percentage of only 5% of cellulose with DS 0.8. The cellulose chains apparently interacted among each other, generating supramolecular structures with aggregated chains in the LiCl/DMAc solvent. The film roughness investigated with AFM was altered by the presence of cellulose in the composite film. For the film obtained with cellulose acetate with GS 1.5, the effects from cellulose as reinforcement were only observed with higher content of cellulose (15%). According to the stress-strain tests, the films may be employed in applications requiring rigid, mechanically resistant materials. Cellulose/chitosan films were also prepared using NaOHaq./thiourea as solvent, in which chitosan served as the matrix. As in the biocomposite with cellulose acetate, the cellulose chains formed domains. The films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), biodegradation tests, humidity sorption isotherms and AFM. The solvent did not affect the crystallinity of the sample, according to the XRD data. Through thermal analysis, it was inferred that the thermal stability was affected by the presence of chitosan in the biocomposite films. The study of biocomposite film degradation in a simulated soil showed that the rate of biodegradation is associated with the crystalline regions of the sample, which are more accessible to the water and the microorganisms. In other words, the higher the crystallinity the lower the biodegradation rate is. It is worth mentioning that the biodegradability also depends on the film morphology. The analysis of AFM images indicated that the film roughness increased with the content of chitosan. The results obtained with the films made with chitosan, cellulose and biocomposites (chitosan/cellulose), as well as for the films from cellulose acetate and cellulose acetate/cellulose, are promising.

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-03-21T13:39:54Z No. of bitstreams: 1 2015 - Arthur Valbon Rodrigues.pdf: 2339821 bytes, checksum: 867f44f511f5a52dfdcf023619e589a9 (MD5) / Made available in DSpace on 2017-03-21T13:39:54Z (GMT). No. of bitstreams: 1 2015 - Arthur Valbon Rodrigues.pdf: 2339821 bytes, checksum: 867f44f511f5a52dfdcf023619e589a9 (MD5) Previous issue date: 2015-08-04 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / In this work six asymmetric thyourea, derived from benzylamine and phenethylamine, were synthesized by reaction of p-substituted phenyl isothiocyanates in the presence of benzylamine and phenethylamine in toluene as solvent by irradiation in ultrasonic bath, featuring the first report in the literature of the adoption of this method for such molecules. The compounds were obtained in high purity, requiring only one recrystallization from hexane/dichloromethane. Yields were very satisfactory, ranging from 89 to 98%. The compounds were characterized by spectroscopic techniques such as 1H, 13C Nuclear Magnetic Resonance and IR. The synthesized compounds were evaluated by electrochemical potentiodynamic polarization techniques, Electrochemical Impedance Spectroscopy and Linear Polarization Resistance as inhibitors to the corrosion AISI 1020 carbon steel in 1M HCl media. Molecular modeling was used for better visualization of the thiourea structures and to correlate theoretical parameters such as the energy of the symmetrical frontier orbital, Mulliken charge on the sulfur atom and dipole moment with the experimental results for corrosion efficiency. In general, all compounds showed corrosion inhibition efficiency with characteristics of mixed inhibitors with anodic trend, however compounds with nitro substituent showed less efficiency, a fact that may be related to their electrons withdrawing potential, which consequently decreases the electron density at the possible center of chemical adsorption, the sulfur atom. However, compounds which showed no substituent and those that contain electron donating group (OCH3) stood out as inhibitors, highlighting N- (p-methoxyphenyl) -N'-phenetylthiourea, which showed 95% efficiency corrosion inhibition, from Electrochemical Impedance spectroscopy. Thus, the asymmetric thiourea benzyl and phenethyl-substituted, especially methoxy-substituted phenyl, can be considered as promising corrosion inhibitors for carbon steel in acid. / Nesse trabalho de disserta??o foram sintetizadas seis tioureias assim?tricas, derivadas da benzilamina e fenetilamina. A obten??o ocorreu atrav?s da rea??o dos isotiocianatos de fenila p-substituidos na presen?a da benzilamina e fenetilamina em tolueno como solvente atrav?s de irradia??o em banho de ultrassom, sendo o primeiro relato na literatura dessa metodologia para tais mol?culas. Os compostos foram obtidos em alto grau de pureza, sendo necess?ria apenas uma recristaliza??o em hexano/diclorometano. Os rendimentos foram muitos satisfat?rios, variando de 89 ? 98%. Os compostos foram caracterizados por t?cnicas espectrosc?picas como Resson?ncia Magn?tica Nuclear 1H,13C e Infravermelho. Os compostos sintetizados foram avaliados atrav?s das t?cnicas eletroqu?micas de Polariza??o Potenciodin?mica, Espectroscopia de Imped?ncia Eletroqu?mica e Resist?ncia a Polariza??o Linear quanto ? a??o como inibidores de corros?o frente a a?o carbono AISI 1020 em HCl 1 mol.L-1. A Modelagem Molecular foi utilizada para melhor visualiza??o das estruturas das tioureias e correlacionar os par?metros te?ricos como a energia dos orbitais de fronteiras sim?tricos, carga de Mulliken no ?tomo de enxofre e momento dipolar com os resultados experimentais da efici?ncia anticorrosiva. De forma geral, todos apresentaram efici?ncia de inibi??o ? corros?o com caracter?sticas de inibidores mistos com tend?ncia an?dica, por?m os compostos com substituinte nitro apresentaram menor efici?ncia, fato esse que pode estar relacionado ao seu poder retirador de el?trons, que consequentemente, diminui a densidade eletr?nica no poss?vel centro de adsor??o qu?mica, o enxofre. Por?m, os compostos que n?o apresentaram substituintes e os que cont?m grupo doador de el?trons (OCH3) se destacaram como inibidores, dando destaque a N-(p-metoxi-fenil)-N?-fenetiltioureia, que apresentou efici?ncia de 95% de inibi??o da corros?o, pela t?cnica de Espectroscopia de Imped?ncia Eletroqu?mica. Assim, as tioureias assim?tricas benzil e fenetil-substitu?das, especialmente met?xi-fenil substitu?das, podem ser consideradas como promissores agentes inibidores da corros?o para o a?o-carbono em meio ?cido.

The thesis entitled “Controlling Stereochemistry at the Quaternary Center Using Bifunctional (Thio)urea Catalysis” is divided into five chapters. Chapter 1: Catalytic Enantioselective Construction of Quaternary Stereocenters through Direct Vinylogous Michael Addition of Deconjugated Butenolides to Nitroolefins The direct use of deconjugated butenolides in asymmetric C–C bond forming reaction is a powerful but challenging task because of the additional problem of regioselectivity along with the issues of diastereo- and enantioselectivity. In this chapter, a direct asymmetric vinylogous Michael addition of deconjugated butenolides to nitroolefins has been demonstrated for the construction of quaternary stereocenter at the γ-position of butenolides. A novel thiourea-based bifunctional organocatalyst, containing two elements of chirality, was synthesized starting from commercially available quinine and (S)-tert-leucine. Remarkably, the sense of stereoinduction in this process is dominated by the tert-leucine segment of the catalyst. Synthetically versatile & highly functionalized γ-butenolides with contiguous quaternary and tertiary stereocenters were synthesized stereoselectively. The reaction was found to be general and a wide range of nitroolefins, with both electron-rich and electron-deficient substituents, underwent smooth reaction under these mild conditions. Similarly, deconjugated butenolides, having various substituents at the γ-position were well tolerated under these reaction conditions and the products were obtained in excellent yields and with uniformly high diastereo- and enantioselectivities. Reference: Manna, M. S.; Kumar, V.; Mukherjee, S. Chem. Commun. 2012, 48, 5193–5195. Chapter 2: Catalytic Asymmetric Direct Vinylogous Michael Addition of Deconjugated Butenolides to Maleimides for the Construction of Quaternary Stereogenic Center In this chapter, a mild and operationally simple protocol for the direct vinylogous Michael addition of deconjugated butenolides to maleimides has been illustrated. Using bifunctional tertiary amino thiourea organocatalyst, derived from a ‘matched’ combination of trans-(1R,2R)-diaminocyclohexane (DACH) and (S)-tert-leucine, the Michael adducts were obtained in excellent yields and with good to high diastereoselectivities and outstanding enantioselectivities. Application of the corresponding diastereomeric catalyst indicated the dominance of the ‘DACH’ unit over the chiral side chain in determining the sense of stereoinduction. The practicality of this protocol is illustrated by substantial low catalyst loading (down to 5 mol%) and one-pot catalyst recycling. Based on the X-ray structure of the catalyst and observed stereochemistry of the Michael adduct, a stereochemical model is proposed which was further supported by additional experiment. Reference: Manna, M. S.; Mukherjee, S. Chem.–Eur. J. 2012, 18, 15277–15282. Chapter 3: Enantioselective Desymmetrization of Cyclopentenedione through Direct Catalytic Vinylogous Michael Addition of Deconjugated Butenolides Five-membered carbocycles containing one or more stereogenic centers on the ring are privileged structural motifs found in many biologically active natural and non-natural compounds. Among various methods for accessing these enantioenriched carbocyclic frameworks, desymmetrization of prochiral or meso-compounds through catalytic enantioselective transformations represents a powerful strategy. The biggest advantage of such asymmetric desymmetrization reactions lies in their ability in controlling stereochemistry remote from the reaction site. This chapter deals with a highly efficient desymmetrization protocol for 2,2-disubstituted cyclopentene-1,3-diones via direct vinylogous nucleophilic addition of deconjugated butenolides with the help of a tertiary amino thiourea bifunctional catalyst. In contrast to the existing desymmetrization protocols, this method represents a unique example where quaternary stereocenter is generated not only within the ring but also outside the cyclopentane ring. Densely functionalized products are obtained in excellent yields and with outstanding diastereo- and enantioselectivities. The robustness screening indicated that the reaction is highly tolerant to a variety of competing electrophiles and nucleophiles. The remarkable influence of the secondary catalyst site on the enantioselectivity points towards an intriguing mechanistic scenario. To the best of our knowledge, this is the first time such an effect is observed in the context of asymmetric catalysis. Reference: (1) Manna, M. S.; Mukherjee, S. Chem. Sci. 2014, 5, 1627–1633. (2) Manna, M. S.; Mukherjee, S. Org. Biomol. Chem. 2015, 13, 18–24. (Perspective) Chapter 4: Enantioselective Desymmetrization of Cyclopentenediones through Organocatalytic C(sp2)–H Alkylation Organic compounds are characterized by the presence of various C–H bonds. Functionalization of a specific C–H bond in a molecule with a selected atom or group are among the most straightforward and desirable synthetic transformations in organic chemistry. In this chapter, a simple protocol for the direct alkylation of olefinic C(sp2)–H bond has been developed, not only enantioselectively using an organocatalyst but more importantly without using any directing group. This alkylative desymmetrization of prochiral 2,2-disubstituted cyclopentene-1,3-diones is catalyzed by a dihydroquinine-based bifunctional urea derivative. Using easily accessible, inexpensive and air-stable nitroalkanes as the alkylating agent, this C(sp2)−H alkylation represents a near-ideal desymmetrization and delivers products containing an all-carbon quaternary stereogenic center in good to excellent yields and with high enantioselectivities. The mild reaction conditions allow for the introduction of various functionalized alkyl groups. The possibility of a second alkylation and its applications has also been demonstrated. This protocol is the first example of the use of nitroalkane as the alkyl source in an enantioselective transformation. It is expected that, these findings would have broader consequences and applications to other alkylative and related transformations. Reference: Manna, M. S.; Mukherjee, S. J. Am. Chem. Soc. 2015, 137, 130–133. (Highlighted in Synform 2015, 67–70) Chapter 5: Enantioselective Desymmetrization of Cyclopentenediones through Organocatalytic Formal C(sp2)–H Vinylation The development of catalytic enantioselective C(sp2)–H vinylation reactions remained relatively underexplored for a long time because of various challenges associated with it. As C(sp2)–H functionalization reactions do not generate any stereocenter at the reaction site, development of enantioselective C(sp2)−H functionalization must rely on desymmetrization of prochiral or meso-substrates. More important issue is the identification of a suitable directing group which can efficiently control the regioselectivity during the activation of C(sp2)−H bond. In this chapter, an efficient formal C(sp2)−H vinylation of prochiral 2,2-disubstituted cyclopentene-1,3-dione is developed without using any directing group. This formal C(sp2)−H vinylation of 2,2-disubstituted cyclopentene-1,3-dione is realized using a two-step operation: catalytic enantioselective Michael addition of deconjugated butenolides followed by a base mediated decarboxylation. The vinylated products, containing a remote all-carbon quaternary stereogenic center, are obtained in good yields and with good to high enantioselectivities. Synthetic utility of this protocol is demonstrated by converting the resulting chiral electron-deficient diene into various important building blocks. Significant erosion in enantioselectivity during the decarboxylation process was explained by a plausible mechanism, which was further supported by control experiments. Reference: Manna, M. S.; Sarkar, R.; Mukherjee, S. manuscript under preparation.

O presente trabalho visou o estudo da modificação química da celulose de linter (obtida de fonte de rápido crescimento e considerada a celulose de maior pureza isolada de fontes vegetais) através da sua derivatização em meio homogêneo, buscando-se a obtenção de materiais com características bem definidas e via um método que apresente boa reprodutibilidade. Dentre os derivados de celulose, os acetatos têm importância industrial significativa. No presente trabalho, acetatos de celulose obtidos no sistema de solvente cloreto de lítio/dimetilacetamida (LiCl/DMAc), com diferentes graus de substituição (GS) foram caracterizados através de 1H NMR, espectroscopia na região do infravermelho, viscosimetria e análises térmicas (DSC e TG). Através de métodos quantitativos aplicados às curvas termogravimétricas pode-se obter parâmetros cinéticos relacionados à decomposição térmica como a energia de ativação (Ea). Os resultados para os acetatos mostraram que conforme o GS aumenta, aumenta o grau de substituição de C2 e C3, e observa-se também aumenta Ea. Acetatos de celulose com diferentes GS foram utilizados para a obtenção de filmes a partir do mesmo sistema de solvente. Visando à obtenção de biocompósitos, filmes de acetatos de celulose com diferentes porcentagens de celulose foram preparados. Nestes filmes, os acetatos são considerados como matriz e a celulose como reforço, se tendo como pressuposto que as cadeias de celulose formarão agregados em solução, os quais serão mantidos nos filmes, atuando então como reforço. Este pressuposto é baseado em resultados de trabalhos anteriores, assim como estudos reológicos feitos no presente trabalho, que mostram que as cadeias de celulose se agregam, mesmo a baixas concentrações. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), cromatografia de exclusão por tamanho (SEC), microscopia eletrônica de varredura (MEV), solvatocromismo, dentre outras. A eliminação dos solventes após a obtenção dos filmes é um fator importante a ser considerado, e os resultados mostraram que o processo escolhido não leva a presença residual dos solventes utilizados. As imagens de MEV indicaram que fibras de celulose nos filmes de biocompósitos no geral não são visíveis em escala microscópica. Este resultado é promissor, pois sugere que as fibras de celulose podem estar presentes em escala nanométrica, já que para alguns filmes a ação como reforço foi observada, através da melhora em algumas propriedades. Ainda, a rugosidade dos filmes de biocompósitos foi alterada com a presença de celulose conforme mostram os resultados de AFM. Os resultados de DMTA indicaram que uma baixa porcentagem de celulose (5% de celulose) no filme de acetato de celulose com GS 0,8, foi suficiente para a ação como reforço ser observada, sugerindo que cadeias de celulose interagiram preferencialmente entre si, gerando estruturas supramoleculares de cadeias agregadas quando ainda no meio solvente (LiCl/DMAc), as quais permaneceram na preparação dos filmes. No entanto, para o filme obtido a partir de um GS maior (GS 1,5), o efeito de reforço da celulose nos filmes de biocompósitos ocorre apenas para a maior proporção de celulose (15% de celulose). Os resultados de ensaio à tração mostraram que dependendo da aplicação, ou seja, a necessidade de filmes mais resistentes à tração e maior rigidez, estes podem ser empregados. Adicionalmente, filmes de celulose e quitosana foram preparados no sistema de solvente NaOHaq./tiouréia. Nestes filmes, considera-se a quitosana como matriz e a celulose como agente de reforço. Acredita-se que as cadeias de celulose prefiram interagir entre si, gerando \"domínios\" de cadeias de celulose. Por este motivo, o termo biocompósito foi empregado também para estes filmes. Estes materiais foram caracterizados via difração de raios X, análises térmicas (DSC, TG e DMTA), biodegradação, sorção de umidade, microscopia de força atômica (AFM), dentre outras. Os resultados de difração de raios X mostram que o sistema de solvente não altera significativamente a cristalinidade dos filmes, comparativamente aos materiais de partida. As análises térmicas empregadas (TG e DSC) mostraram que a estabilidade térmica é alterada devido a presença dos dois polissacarídeos nos filmes de biocompósitos. O estudo de biodegradação dos filmes de biocompósitos em solo simulado mostrou que a velocidade de biodegradação está relacionada à proporção das regiões não cristalinas, que são mais acessíveis à água e aos microrganismos, isto é, quanto maior o valor de índice de cristalinidade, menor será a velocidade de biodegradação. Importante ressaltar que o comportamento destes filmes em relação à biodegradação está também relacionado com a morfologia apresentada pelos filmes. A análise de AFM mostrou que o aumento da proporção de quitosana nos filmes de biocompósitos leva a maiores valores de rugosidade. Os resultados obtidos para os filmes de quitosana, celulose e biocompósitos (quitosana/celulose), assim como para os filmes de acetato de celulose, celulose e biocompósitos (acetato de celulose/celulose) se mostraram promissores. / This work was aimed at studying the chemical modification of linters cellulose extracted from a source of rapid growth and considered the most pure cellulose from vegetable sources. Derivatization was carried out in a homogeneous medium to obtain materials with well-defined properties via a reproducible method. Here cellulose acetate was obtained with various degrees of substitution (DS) using the lithium chloride/dimethylacetamide system (LiCl/DMAc), being characterized with 1H NMR, infrared spectroscopy, viscometry measurements and thermal analysis (DSC and TG). The thermogravimetric curves were analyzed quantitatively, which allowed the determination of kinetics parameters for the thermal decomposition, including the activation energy (Ea). Ea and the substitution at C2 and C3 increased with increasing DS. Cellulose acetates with distinct DS were obtained in the form of films using the solvents mentioned above. Furthermore, biocomposite films were prepared with different contents of cellulose, in which the acetates were considered as matrices and the cellulose was the loading material. It is assumed that the cellulose chains form aggregates in solution, which will be preserved in the films, thus acting as reinforcement. This hypothesis was based on previous work and confirmed here with rheological data. We show that the cellulose chains are aggregated even at low concentrations. These films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), size exclusion chromatography (SEC), atomic force microscopy (AFM) and scanning electron microscopy. No residual solvent was present after film preparation. The SEM images indicated that the cellulose fibers in the biocomposite films are not visible at the microscopy scale, thus suggesting the presence of cellulose nanofibers. This is promising due to the possible enhancement in the mechanical properties, which was actually observed with a threshold percentage of only 5% of cellulose with DS 0.8. The cellulose chains apparently interacted among each other, generating supramolecular structures with aggregated chains in the LiCl/DMAc solvent. The film roughness investigated with AFM was altered by the presence of cellulose in the composite film. For the film obtained with cellulose acetate with GS 1.5, the effects from cellulose as reinforcement were only observed with higher content of cellulose (15%). According to the stress-strain tests, the films may be employed in applications requiring rigid, mechanically resistant materials. Cellulose/chitosan films were also prepared using NaOHaq./thiourea as solvent, in which chitosan served as the matrix. As in the biocomposite with cellulose acetate, the cellulose chains formed domains. The films were characterized using X-ray diffraction, thermal analysis (DSC, TG and DMTA), biodegradation tests, humidity sorption isotherms and AFM. The solvent did not affect the crystallinity of the sample, according to the XRD data. Through thermal analysis, it was inferred that the thermal stability was affected by the presence of chitosan in the biocomposite films. The study of biocomposite film degradation in a simulated soil showed that the rate of biodegradation is associated with the crystalline regions of the sample, which are more accessible to the water and the microorganisms. In other words, the higher the crystallinity the lower the biodegradation rate is. It is worth mentioning that the biodegradability also depends on the film morphology. The analysis of AFM images indicated that the film roughness increased with the content of chitosan. The results obtained with the films made with chitosan, cellulose and biocomposites (chitosan/cellulose), as well as for the films from cellulose acetate and cellulose acetate/cellulose, are promising.

Ce travail de thèse porte sur la synthèse de nouveaux composés chiraux à partir de l’isosorbide et de l’isomannide en vue de leurs applications en catalyse asymétrique. Dans une première partie, de nouvelles monophosphines ont été synthétisées et appliquées en tant que ligands dans la réaction d'hydrogénation asymétrique d’oléfines. Des excès énantiomériques jusqu’à 96% ont été observés. Elles ont également été employées en tant que catalyseurs organiques dans les réactions de cyclisation [3 +2]. De bonnes activités catalytiques et des excès énantiomériques modestes sont obtenus. Dans une deuxième partie, une série de composés azotés chiraux a été synthétisée en 3 à 4 étapes avec de bons rendements globaux. Ils ont été testés en tant que ligands dans la réaction de réduction de cétones aromatiques par transfert d’hydrogène. Des excès énantiomériques jusqu’à 73% ont été obtenus. La réaction d’addition de phénylacétylène sur d’imines a également été étudiée. Les complexes formés se sont montrés actifs mais pas très énantiosélectifs. Ces composés azotés ont également été utilisés en tant que catalyseurs organiques dans la réaction d’addition de Michael de cétones aromatiques sur le nitrostyrène. Toutefois, ils n’ont permis de conduire qu’à de faibles énantiosélectivités. Dans une dernière partie, des composés de type thiourée ont été synthétisés en 5 étapes. Ces thiourées ont été appliquées en catalyse organique dans la réaction d’alkylation de type Friedel-Crafts entre différents substrats indoliques et nitrooléfines, et dans la réaction d’addition conjuguée des hydroxylamines sur des pyrazoles pour la synthèse de dérivés β-aminoacides. Ces catalyseurs se sont révélés actifs mais peu énantiosélectifs. / The Thesis deals with the synthesis of new chiral compounds derived from isosorbide and isomannide and their applications to asymmetric catalysis. The first part of this work consisted in perfecting the chemical and enantioselective hydrogenation conditions of olefins using chiral monophosphines as ligands (up to 96% ee). These phosphines were also used as organocatalysts for [3+2] cyclisation reactions showing good catalytic activity and moderate enantioselectivity. The second part turned to the synthesis of a series of chiral nitrogen compounds which were evaluated in the asymmetric transfer hydrogenation of aromatic ketones giving good enantioselectivity (up to 73% ee). The complexes formed with amine ligands were also applied to the addition reaction of phenylacetylene to imines. Good catalytic activity but low enantioselectivity were observed. These nitrogen compounds were also used as organocatalysts in the Michael addition reaction of aromatic ketones to the nitrostyrene. Again, low enantiomeric excess was obtained. The last part of this work consisted in preparing new chiral thiourea compounds which were applied as organocatalysts to the Friedel-Crafts alkylation reaction of different indoles with nitroolefines, and to the conjugate addition reaction of hydroxylamines to pyrazoles derivatives for the synthesis of β-amino acids. In two cases, these catalysts have proved active but not enantioselective.