Compostos de organoselênio como catalisadores em reações de substituição nucleofílica e avaliação antimicrobiana de líquidos iônicos contendo selênio

Abstract

Organic compounds derived from selenium have gained significant importance due to their versatility. This work is divided into two chapters, in which the chemical and biological importance of these compounds is explored. The first chapter describes two strategies for the efficient synthesis of organic thiocyanates and selenocyanates through nucleophilic substitution reactions. In the non-catalyzed approach, benzyl halides were utilized as substrates with ethanol as a solvent. After a 4-hour reaction time, 19 thiocyanates and 9 selenocyanates were obtained with yields ranging between 35% and 93%. On the other hand, in the catalyzed reaction, 11 selenium organocatalysts were prepared, including selenides and selenonium salts. The latter proved to be the most efficient catalyst, as it forms chalcogen bonds with the substrates. By employing a catalytic amount of selenonium salt (10 mol%), a mixture of water and dimethylcarbonate (20:1) as the solvent, 2 equivalents of the nucleophilic species, and a reaction time of only 10 minutes, 13 thiocyanates and 14 organic selenocyanates were obtained with yields ranging between 36% and 94%. Chapter II presents the synthesis of a series of ionic liquids using previously described methodologies. Five ionic liquids containing selenium were synthesized, and their antimicrobial potential was evaluated. The results obtained indicated that all compounds studied showed antimicrobial activity against Cryptococcus neoformans H99, Cryptococcus gattii R265, Candida albicans, and Candida krusei. Moreover, it was observed that the presence of the selenium atom in the molecule played a crucial role in the antimicrobial activity of these compounds.