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No intuito de subsidiar e orientar futuras pesquisas astroquímicas pela busca de novas espécies moleculares, foram calculadas diversas propriedades em nível CCSD/cc-pVQZ (como geometrias, cargas atômicas, momentos de dipolo, frequências vibracionais e intensidades fundamentais de infravermelho) de bases de Lewis (B) presentes no meio interestelar (B = CO, CS, SO, HCN, FCN, ClCN, BrCN, HNC, FNC, ClNC, BrNC, OCS, HCNO HOCN, HONC, HNCO, NCCN e CNNC) e de suas espécies protonadas. Além disso, o modelo Carga - Fluxo de Carga - Fluxo de Dipolo (CFCFD), em termos dos multipolos da Teoria Quântica de Átomos em Moléculas (QTAIM), foi empregado para o estudo das variações nas intensidades de infravermelho de modos de estiramento durante a protonação. Os resultados indicam que, dependendo da extremidade da molécula na qual o próton se liga, há fortalecimento ou enfraquecimento das bandas de infravermelho originais. Estes fenômenos parecem estar associados à alteração de carga inicial durante a protonação, com fluxos de carga e de dipolo coordenados com tais mudanças de carga iniciais durante as vibrações. No que concerne ao estiramento da ligação formada após a protonação, [B-H]+, a contribuição de carga é preponderante quando o próton se liga aos átomos mais eletronegativos e menos polarizáveis (O, N e F). Todavia, quando o próton se liga ao par eletrônico isolado do carbono (isonitrilas, CO e CS) ou a outros átomos como cloro, bromo e enxofre, a contribuição de fluxos de carga e de dipolo atômico se tornam mais relevantes. De qualquer maneira, a raiz quadrada da intensidade de infravermelho desta nova banda de absorção correlaciona-se com a carga do próton de forma linear. No que se refere à partição da energia eletrônica por meio da aproximação de Átomos Quânticos Interagentes, verifica-se que: (1) a energia de estabilização do próton é proporcional à carga eletrônica recebida da base; (2) a desestabilização da base aumenta quanto maior a quantidade de carga eletrônica doada para o próton e (3) a energia de interação dos fragmentos é bastante específica de cada sistema, o que origina uma separação em grupos de sistemas semelhantes. / In order to support and guide future astrochemical research related to the search for new molecular species, some properties were calculated at the CCSD/cc-pVQZ level (such as geometry, atomic charges, dipole moments, vibrational frequencies and fundamental infrared intensities) for Lewis bases (B) present in the interstellar medium (B = CO, CS, SO, HCN, FCN, ClCN, BrCN, HNC, FNC, ClNC, BRNC, OCS, HCNO, HOCN, HONC, HNCO, NCCN and CNNC) and its protonated species. In addition, the Charge - Charge Flux - Dipole Flux (CCFDF) model in terms of multipoles from the Quantum Theory of Atoms in Molecules (QTAIM) was used to study the variations in the infrared intensities of stretching modes during protonation. The results indicate that there is strengthening or weakening of the original infrared bands depending on the molecule end to which the proton is attached. These phenomena appear to be associated with the initial redistribution of electronic charge during protonation, resulting in charge and dipole fluxes coordinated with such initial rearrangement during the vibrations. Moreover, regarding the stretching intensity of the bond formed after protonation, [BH]+, the charge contribution is predominant when the proton is bound to atoms more electronegative and less polarizable atoms (O, N and F). However, when the proton binds to the lone (electron) pair of carbon (isonitriles, CO and CS) or to other atoms such as chlorine, bromine and sulfur, the charge and dipole fluxes become more significant. Nevertheless, the square root of the intensity for this new infrared absorption band correlates linearly with the charge assumed by the proton. Finally, with respect to the electronic energy partition through the Interaction Quantum Atom proposal, it is seen that (1) the proton stabilization energy is proportional to the electronic charge received from the base; (2) the destabilization of the base increases in line with the amount of electronic charge lost to the proton and (3) the interaction energy between the fragments is very specific of each system, which results in group separations.

Several workers have reduced acidic polysaccharides for structural studies, for sorption studies, and for studies on chemical reactivity. All these investigators have used reduction procedures which have not been extensively studied and do not completely reduce the acidic groups. In addition, it is not known to what extent the other functional groups such as esters and hemiacetal are reduced. The goal of the present study is to obtain a further understanding of the reduction with both a Lewis acid, diborane, and a Lewis base, lithium borohydride, by comparison of the percent reduction of the functional groups on an acidic polysaccharide. Alginic acid from the stipes of the brown algae Laminaria hyperborea was selected as the acidic polysaccharide for study.

No intuito de subsidiar e orientar futuras pesquisas astroquímicas pela busca de novas espécies moleculares, foram calculadas diversas propriedades em nível CCSD/cc-pVQZ (como geometrias, cargas atômicas, momentos de dipolo, frequências vibracionais e intensidades fundamentais de infravermelho) de bases de Lewis (B) presentes no meio interestelar (B = CO, CS, SO, HCN, FCN, ClCN, BrCN, HNC, FNC, ClNC, BrNC, OCS, HCNO HOCN, HONC, HNCO, NCCN e CNNC) e de suas espécies protonadas. Além disso, o modelo Carga - Fluxo de Carga - Fluxo de Dipolo (CFCFD), em termos dos multipolos da Teoria Quântica de Átomos em Moléculas (QTAIM), foi empregado para o estudo das variações nas intensidades de infravermelho de modos de estiramento durante a protonação. Os resultados indicam que, dependendo da extremidade da molécula na qual o próton se liga, há fortalecimento ou enfraquecimento das bandas de infravermelho originais. Estes fenômenos parecem estar associados à alteração de carga inicial durante a protonação, com fluxos de carga e de dipolo coordenados com tais mudanças de carga iniciais durante as vibrações. No que concerne ao estiramento da ligação formada após a protonação, [B-H]+, a contribuição de carga é preponderante quando o próton se liga aos átomos mais eletronegativos e menos polarizáveis (O, N e F). Todavia, quando o próton se liga ao par eletrônico isolado do carbono (isonitrilas, CO e CS) ou a outros átomos como cloro, bromo e enxofre, a contribuição de fluxos de carga e de dipolo atômico se tornam mais relevantes. De qualquer maneira, a raiz quadrada da intensidade de infravermelho desta nova banda de absorção correlaciona-se com a carga do próton de forma linear. No que se refere à partição da energia eletrônica por meio da aproximação de Átomos Quânticos Interagentes, verifica-se que: (1) a energia de estabilização do próton é proporcional à carga eletrônica recebida da base; (2) a desestabilização da base aumenta quanto maior a quantidade de carga eletrônica doada para o próton e (3) a energia de interação dos fragmentos é bastante específica de cada sistema, o que origina uma separação em grupos de sistemas semelhantes. / In order to support and guide future astrochemical research related to the search for new molecular species, some properties were calculated at the CCSD/cc-pVQZ level (such as geometry, atomic charges, dipole moments, vibrational frequencies and fundamental infrared intensities) for Lewis bases (B) present in the interstellar medium (B = CO, CS, SO, HCN, FCN, ClCN, BrCN, HNC, FNC, ClNC, BRNC, OCS, HCNO, HOCN, HONC, HNCO, NCCN and CNNC) and its protonated species. In addition, the Charge - Charge Flux - Dipole Flux (CCFDF) model in terms of multipoles from the Quantum Theory of Atoms in Molecules (QTAIM) was used to study the variations in the infrared intensities of stretching modes during protonation. The results indicate that there is strengthening or weakening of the original infrared bands depending on the molecule end to which the proton is attached. These phenomena appear to be associated with the initial redistribution of electronic charge during protonation, resulting in charge and dipole fluxes coordinated with such initial rearrangement during the vibrations. Moreover, regarding the stretching intensity of the bond formed after protonation, [BH]+, the charge contribution is predominant when the proton is bound to atoms more electronegative and less polarizable atoms (O, N and F). However, when the proton binds to the lone (electron) pair of carbon (isonitriles, CO and CS) or to other atoms such as chlorine, bromine and sulfur, the charge and dipole fluxes become more significant. Nevertheless, the square root of the intensity for this new infrared absorption band correlates linearly with the charge assumed by the proton. Finally, with respect to the electronic energy partition through the Interaction Quantum Atom proposal, it is seen that (1) the proton stabilization energy is proportional to the electronic charge received from the base; (2) the destabilization of the base increases in line with the amount of electronic charge lost to the proton and (3) the interaction energy between the fragments is very specific of each system, which results in group separations.

Novel bis(tetrahydroisoquinoline) N,N'-dioxides 1,2 belong to the group of compounds with axial chirality that act as a Lewis base. These properties make them useful chiral catalysts in reactions such as allylation, opening of epoxides, etc. that exhibit high enantioselectivity. The prepared chiral bis(tetrahydroisoquinoline) N,N'-dioxides (R,Rax,R)-1, (R,Sax,R)-1, (Rax,R)-2 a (Sax,R)-2 were tested as catalysts in enantioselective allylation of variously substituted α,β−unsaturated aldehydes and dienals with allyltrichlorosilane (Scheme 1). All the catalysts exhibited high catalytic activity as well as high asymmetric induction (up to 96% for α,β- unsaturated aldehydes;1 up to 98 % for dienals). Appropriate choice of solvent as a reaction medium3,4 and substitution in α-position in aldehydes were the crucial factors for the successful course of the reaction. The catalytic activity of (R,Rax,R)-1 and (R,Sax,R)-1 was also tested in asymmetric opening of meso-epoxides with tetrachlorosilane (ee up to 69 %) (Scheme 2). N N O O O O 1 N N O O O 2 Scheme 1 Scheme 2 1) Vlašaná, K.; Hrdina, R.; Valterová, I.; Kotora, M. Eur. J. Org. Chem. 2010, 7040. 2) Kadlčíková, A.; Hrdina, R.; Valterová, I.; Kotora, M. Adv. Synth. Catal. 2009, 351,1279. 3) Hrdina, R.; Opekar, F.; Roithová, J.; Kotora, M. Chem. Commun....

In the diploma thesis, a method for preparation of the unsaturated C15-C20 tiacumicin fragment was developed. Tiacumicin is classified as a macrolidone antibiotic. Although three syntheses of tiacumicin have been recently published, this study has aimed to develop a novel pathway for its preparation utilizing catalytic reactions instead of stoichiometric ones. In the second part, an enantioselective allylation of (E)-3-jod-2-methylpropenal has been developed applying catalysis by a series of N,N'-dioxide catalysts. The asymmetric induction achieved in the allylation was up to 99% ee. This procedure allows relatively simple, straightforward and efficient preparation of wide range of natural products. Keywords tiacumicin, asymmetric synthesis, allylation, catalysis, chiral Lewis bases, organocatalysis