Metal-catalyzed cycloadditions of alkynes with isocyanates or nitriles are valuable tools for the synthesis of complex carbocycles and heterocycles. Although this transformation has been studied for over three decades, the cyclizations of disocyanates with 1,3-dienes or allenes are not known and the asymmetric cycloadditions of isocyanates are scarce. To expand the scope of these powerful reactions, we studied the semi-intramolecular metal-catalyzed cycloaddition of several unsaturated systems with isocyanates. Our results show that further work in this area is needed to suppress the formation of undesired homo-coupled adducts and obtain the bicyclic products in a more efficient manner. 1,3-butadienes are versatile building blocks in organic synthesis. Therefore, it is our interest to develop an efficient method for their preparation making 1,3-butadienes more available for the organic chemist. A number of methods are known for the synthesis of these compounds, but the majority of them present problems such as poor regioselectivity, low atom economy, or require the use of toxic or non-readily available reagents. In order to develop a more effective synthesis, we employed (allenylmethyl)silanes as intermediates for the preparation of 1,3-butadienes utilizing (4-bromobut 2-ynyl)trimethylsilane as a diene equivalent. A Nozaki-Hiyama-Kishi type transformation was used for the highly regioselective preparation of (trimethylsilyl)methylallenic alcohols from aldehydes and ketones. In addition, several tridentate bis(oxazolinyl)carbazole ligands were synthesized and used for the enantioselective synthesis of allenic alcohols. Carbazole ligands synthesis was achieved by the Suzuki coupling of carbazoles with different boronic acids followed by carbonylative amidation and cyclization. We report an efficient new method for the desilylation of allenic alcohols providing a variety of secondary and tertiary 1,3-butadienylcarbinols. Furthermore, our interest in extending this methodology led us to the discovery of a novel synthesis of 2-aminomethyl-1,3-dienes from N-tosyl imines.

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Thesis advisor: James P. Morken / The first examples of an enantioselective allene diboration and diene diboration are reported. The asymmetric palladium-catalyzed allene diboration afforded 1,2- bis(boronate)esters in up to 98% ee. The reaction development for the allene diboration, as well as the expansion of the substrate scope, and elucidation of the reaction mechanism are reported. Following the development of the enantioselective allene diboration, the first enantioselective diene diboration was disclosed. 1,4-Dihydroxylation products resulting from a tandem diene diboration/oxidation sequence are obtained in up to 92% ee. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Amir H. Hoveyda / A general method for the catalytic enantioselective addition of silylallenes to phosphinoyl aldimines has been developed. Reactions are promoted in the presence of 5.0 mol% of an N–heterocyclic carbene–copper complex and a silyl-protected propargyl boron reagent. The reaction is efficient, requiring only 10 minutes, highly group selective, enantioselective and products can be further functionalized. Utility is highlighted in the total synthesis of marine alkaloid (S)-(–)-cyclooroidin using our product as a key intermediate in the total synthesis. The catalytic enantioselective addition of a 1,3-butadiene has been developed using a homoallenylboron reagent. These transformations are promoted by a C1-symmetric N–heterocyclic carbene–copper complex within 4 hours. Products can be obtained with gamma selectivity to afford the diene containing product. Efforts have been expanded towards the application of our product as a key intermediate towards the total synthesis of (+)-homochelidonine. Key transformations include a highly selective 1,2-protoboration of the 1,3-diene product followed by a Pd-catalyzed intramolecular sp2-sp3 Suzuki cross coupling. The development of a general catalytic enantioselective method for the propargyl addition to trifluoroketones has been studied. Reactions are complete within 15 minutes, broadly applied to alkyl-, alkenyl, alkynyl, aryl, and heteroaryl-substituted trifluoroketones, highly enantioselective and group selective. Key findings include use of an aminophenol containing an electron-withdrawing to improve reactivity and enantioselectivities. The method can be carried out on gram scale and has been applied to a substrate which can be elaborated towards glucocorticoid agonist BI 653048. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

A library of iridium complexes featuring oxazoline and imidazol-2-ylidene ligands were synthesized by reaction of a library of imidazoles with a second library of oxazoline iodides. These complexes were active catalysts for hydrogenations of aryl substituted monoenes. Tri- and 1,1-disubstituted alkenes were hydrogenated quantitatively with ee??s up to 99% at 1 atm hydrogen pressure. Catalyst, substrate, temperature and pressure effects were studied. The iridium complexes were also used for the kinetic study of hydrogenation of 2,3- diphenylbutadiene. This hydrogenation is a stepwise reaction: one double bond was hydrogenated first, then the second one. Both step hydrogenations were zero order in alkene. The consumption of 2,3-diphenylbutadiene was first order in catalyst, and probably first order in hydrogen pressure too. The enantioselectivity for the first step hydrogenation was low. There were match and mismatch catalyst-substrate relationships for the second step hydrogenation, and the enantioselectivities for this step were catalyst controlled. NMR studies indicated that the initiation of the reaction involved both hydrogen and alkene substrate. A competitive experiment was designed to explore the formation of meso-alkane at first step hydrogenation, and the results indicated that the alkane was formed predominantly via an associative mechanism. Four types of conjugate dienes were synthesized and hydrogenated. Different reactivities and selectivities were obtained for each type of dienes. In the best case, a diene was hydrogenated quantitatively with an excellent ent/meso ratio of 20:1.0 and 99% enantioselectivity. The scope, limitation and potential applications of the reactions were discussed. A selection of the dienes was hydrogenated with the Crabtree??s catalyst, for comparison, and the yields, conversions and diastereoselectivities were inferior to those from iridium-oxazoline-imidazol-2-ylidene catalysts.

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>Magister Scientiae - MSc / This thesis focuses on the electroanalysis of some dienes (2-methyl-1.3-butadiene (MBD), tran-1.3-pentadiene (PD), 1.3-cyclohexadiene (CHD) and 3-cyclooctadiene (COD)) found in gasoline and the development of simple electrochemical diene sensors. The detection of dienes in fuels is important as they readily polymerise and form gum in fuel tanks. The electroctivity of the dienes was studied with glassy carbon electrode (GCE) and Pt electrode in tetrabutylammonium perchlorate (TBAP)/acetonitrile solution. Polyaniline-polystyrene sulfonic acid (PANi-PSSA) composite films were electro-deposited or drop-coated on GCE, with and without gold nanoparticles (AuNPs) and characterized by cyclic voltammetry (CV), high resolution transmission electron microscopy (HRTEM) and ultraviolet-visible (UV-vis) spectroscopy. Both composite polymers were found to be of nanofibral structure, and the spherical gold nanoparticles were dispersed uniformly within the polymer. The dienes exhibited no redox peaks on GCE/PANi-PSSA and GCE/PANi-PSSA/AuNPs electrode systems from -1.0 V to +1.5 V, beyond which PANi would overoxidize and lose its electroactivity. Therefore, cyclic voltammetry and steady state amperometry of the four dienes (MBD, PD, CHD and COD) were studied with unmodified Pt and GCE electrodes. Subtractively normalised interfacial-fourier transform infra-red (SNIFTIR) spectroscopic studies of the dienes were performed with Pt electrode. SNIFTIR data showed that there was a definite electro-oxidation of 1.3-cyclohexadiene as electrode potential was changed from E = 770 mV to E = 1638 mV. Severe electrode fouling was observed when steady state amperometric detection of CHD, as a representative diene, was performed on Pt electrode. Randel-Sevčik analysis of the CVs of the dienes on Pt electrode gave diffusion coefficient (Dox) values of 10.65 cm²/s, 9.55 cm²/s, 3.20 cm²/s and 3.96 cm²/s for CHD, COD, PD, and MBD, respectively. The corresponding detection limits (3σn-1) were 0.0106 M, 0.0111 M, 0.0109 M, and 0.0107 M.

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Made available in DSpace on 2014-12-17T14:36:28Z (GMT). No. of bitstreams: 1 AdailsonTM_TESE.pdf: 5900813 bytes, checksum: db354a9f57b24c6b32d8cbb3277e0f58 (MD5) Previous issue date: 2012-03-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The study was aimed to test a teaching module on the Zoltan Paul Dienes theory, focusing on the content: The transformation of measurements: length, areas and volumes. The study based on constructivist theory consisted in a methodological intervention with students of the 7th period of the Course of Pedagogy, in Central Campus, Federal University of Rio Grande do Norte (UFRN). A preliminary study with 40 students called diagnostic evaluation found that students did not understand the concept of measurements transformation and its processing steps. The latter was performed only with the help of the table of measurements transformation with no understanding of the content. He applied a pretest, a set of activities and a post-test. The latter was used as a tool for evaluation of the student learning process. The answers of these ones were evaluated according to the concept of reflective abstraction of Jean Piaget, one of the authors who influenced the Dienes theory / A pesquisa teve como objetivo geral testar um m?dulo de ensino baseado na teoria de Dienes, focalizando o conte?do de transforma??o de medidas de comprimento, ?rea e volume. O estudo baseado na teoria de Zoltan Paul Dienes consistiu numa interven??o metodol?gica com alunos do Curso de Pedagogia da Universidade Federal do Rio Grande do Norte (UFRN). Um estudo preliminar com 40 alunos denominado avalia??o diagn?stica verificou que os alunos n?o compreendiam o conceito de transforma??o de medida, mas somente aplicavam a tabela de convers?o de medidas. A interven??o metodol?gica foi levada a efeito na turma de Pedagogia do 7? per?odo da UFRN. Aplicou-se um pr?-teste, um conjunto de atividades de ensino e um p?s-teste. Este ?ltimo foi utilizado como instrumento de avalia??o da aprendizagem dos alunos. As respostas dos alunos foram avaliadas segundo o conceito de abstra??o reflexionante de Jean Piaget, um dos autores que influenciou a teoria de Zoltan Paul Dienes