In this work, a visible-light-driven synthesis of alkynyl selenides using [BMIm]BF4 as an environmentally friendly solvent and without the addition of metal catalysts, photosensitizers, directing-groups, or bases is reported. The target compounds were obtained in moderate to good yields with good functional group tolerance by the reaction of diorganoyldiselenides with 1-bromoalkynes proceeding through a radical mechanism.

In this work, we report the preparation of a copper-silica material (Cu/SiO2) by a sol-gel methodology and its characterization concerning composition and textural properties. The Cu/SiO2 material was successfully applied as a Lewis acid heterogeneous catalyst for the A3-coupling from 2-aminopyridine, aldehydes and alkynes to imidazo[1,2-a]pyridines (45-82%), which are relevant pharmacological scaffolds. The synthesis shows a number of advantages, such as easy separation from the reaction media and the minimal formation of metal aqueous wastes. Investigation of the mechanism supports the involvement of the formation of reaction intermediates inside the pores of the mesoporous material prior to 5-exo-dig cyclization.

Uma nova família de ésteres tiazolínicos e tiazóis foram sintetizados e as propriedades térmicas são apresentadas e discutidas. Os ésteres tiazolínicos foram obtidos pela reação de ciclização de benzonitrilas 4-substituídas com o amino ácido L-cisteína seguido da reação de esterificação com álcoois e fenol previamente selecionados. A oxidação dos ésteres tiazolínicos mediado pelo reagente BrCCl3/DBU permitiu a transformação dos respectivos ésteres tiazolínicos em ésteres tiazóis . Os compostos finais dos ésteres tiazolínicos e tiazóis são formados por cadeias alquílicas, (perfluoroalquil)alquílicas e p-alcoxifenilas. Alguns cristais líquidos mostraram serem mais relevantes. Um deles apresentou mesofase esmética A (SmA) monotrópica enquanto que outros apresentaram mesofase estável SmA. Como esperado, as cadeias de alcanos semifluorados induziram a formação de mesofase ortogonal via efeito de segregação.

A new family of thiazoline and thiazole esters has been synthesized and their thermal properties are presented and discussed. Thiazoline esters were obtained by cyclization reaction from 4-substituted benzenenitrile and amino acid L-cysteine followed by esterification reaction with selected alcohols and phenol. Subsequent oxidation step to transform thiazoline esters into thiazole esters was applied mediated by BrCCl3/DBU. The final thiazoline and thiazole esters are composed by terminal flexible hydrogenated alkyl chain from one side and to the other side by terminal segments of flexible alkyl chains (hydrogenated chain), (perfluoralkyl)alkyl chains (semifluorinated alkane) p-alkoxyphenyl chains. Some liquid crystals compounds for thiazoline and thiazole esters showed to be relevant. One of the thiazoline esters display a monotropic smectic A (SmA) mesophase while some thiazole esters show stable SmA mesophase. As expected semifluorinated alkane chain induce the formation of orthogonal mesophase by means of segregation effect.

Uma série de calcogeno ésteres, 1a, 6a e 6b foi obtida em uma rota sintética conveniente. A análise de microscopia óptica de luz polarizada (POM) e calorimetria diferencial de varredura (DSC) mostrou que estes calcogeno ésteres apresentam uma ampla faixa de mesofase nemática. Além disso, espectros de absorção na região do UV-Vis em solução (ca.10-5 mol L-1) também foram obtidos de maneira a se obter a diferença de energia entre os orbitais moleculares HOMO-LUMO, para posterior comparação com os resultados teóricos. Os valores calculados para o gap de HOMO-LUMO estão de acordo com os valores experimentais obtidos, onde a eletronegatividade do heteroátomo (O, S e Se) deve ser o principal fator para a localização do máximo de absorção. Um estudo teórico foi realizado utilizando cálculos de DFT/B3LYP com método híbrido de Becke aplicando uma correlação funcional de Lee-Yang-Parr (B3LYP) com a base DGDZVP a fim de avaliar algumas propriedades físico-químicas relacionadas com o mesomorfismo e as propriedades eletrônicas espectrais. Através da síntese destes compostos, a influência do átomo de calcogênio nas propriedades fotofísicas e mesomórficas pôde ser avaliada de uma forma mais precisa.

A series of chalcogeno esters 1a, 6a and 6b have been synthesized in a straightforward manner. Polarized-light optical microscopy (POM) and differential scanning calorimetry (DSC) showed that these chalcogeno esters displayed a wide nematic range of mesophase. In addition, UV-Vis in solution (ca.10-5 mol L-1) was applied in order to obtain the HOMO-LUMO gap for further comparison with the theoretical results. The calculated values to the HOMO-LUMO gap are in excellent agreement with the experimental results, where the electronegativity of the heteroatom (O, S and Se) seems to play a fundamental role in the absorption maxima location. A theoretical study was performed using a DFT/B3LYP calculations with Becke's three-parameter hybrid method applying the Lee-Yang-Parr functional correlation (B3LYP) with DGDZVP basis set in order to evaluate some physical chemistry data related with mesomorphic and spectral eletronic properties. By synthesizing these compounds we were able to get a more precise description about the influence of the chalcogen atom on the mesomorphic and photophysical properties.