Catálise micelar na síntese de derivados oxazolínicos potencialmente bioativos

Abstract

The evolution of science over the centuries improved the development of chemistry that originally depended of natural substances. Through the years, natural products have become inspiration for the development of new compounds and the number of semisynthetic and synthetic substances was increasing. In this sense, in the most of the synthetic methodologies have been made use of chemicals that cause great environmental impact and it are harmful to health. Thus, the principles of Green Chemistry become increasingly relevant and and water could be used as solvent by micellar catalysis, because it is cheap, usually available, non-flammable, non-toxic and does not pollute the environment. In this work, one of the goals was the synthesis of oxazoline compounds (9 and 10) in micellar solutions and comparing the results obtained with the traditional method. The oxazolines were obtained by methodologies described in the literature, however the water reactions did not lead to the formation of products, even with changes in surfactant concentration, nature of the products, temperature and ionic strength of the medium. Another aim of this work was the preparation of a hybrid between the oxazoline (9) and nitroaromatic compounds. The reaction between 9 and 2,6-dichloro-nitropyridine (14) led to the hybrid (17) with chlorine being substituted at C-6 position of the pyridine ring. The reaction did not occur at the reactive position (C-2) in a nucleophilic aromatic substitution (SNAr), possibly by steric factors. Finally, compound 17 was prepared using micellar catalysis by the surfactants Brij 30 (2 and 4%), Triton (2 and 4%) and SDS (5%) in an aqueous medium. These results are promising because they prove that the SNAr reaction can be performed on "green solvents" contributing to the development of synthetic methodologies more mild to the environment.