Síntese de tiazolidinonas e tiazinanonas, potenciais agentes antioxidantes

Abstract

In this work is presented the synthesis of 1,3-thiazolidin-4-ones and 1,3- thiazinan-4-ones derivatives of 2-picolylamine and their evaluation as potential antioxidants. The reaction of heterocycles occurs between the 2- picolylamine-, substituted benzaldehydes and mercaptoacetic acid to obtain the thiazolidinones (5- membered heterocycle), and mercaptopropionic acid to obtain the tiazinanonas (6- membered heterocycle). The heterocycles were synthesized by standard methodology in one step (one-pot) using the Dean Stark apparatus for azeotropic removal of water in a period of 16 hours. Searching for an alternative approach, with less residual and reduced reaction time, was also fulfilled the synthesis using an unconventional methodology via ultrasound irradiation. Reactions via ultrasound were also performed in a single step in only 10 minutes. All substances obtained, 31 heterocycles, are unprecedented in the literature. The thiazolidinones obtained with conventional methodology have higher yields (43-99%) when compared to ultrasound methodology (52-95%), but the use of ultrasound is more efficient due to the large reduction in reaction time, which improved from 16h to 10 min, besides the reduction of residual generation. The tiazinanonas were synthesized by conventional methodology and present yields in the range of 40-92%. All products were identified by Gas Chromatography (GC) and characterized by Nuclear Magnetic Resonance (NMR) 1H and 13C. Additionally, tests were performed for antioxidant activity of the synthesized compounds. The substances were evaluated for their ability to capture radicals DPPH (2,2-diphenyl-1-picryl-hidrazil) and ABTS (2,2 'azinobis (3-ethylbenzotiazolino-6-sulfonic acid) diammonium salt). Compounds 4p (R= 2-CN) and 6a (R=2-NO2) showed the best results against DPPH and compound 6m (R=2-OH) showed the best results against ABTS.