Cachaça como solvente alternativo em reações multicomponentes

Abstract

Cachaça is a widely known alcoholic beverage used in the preparation of various drinks. It is produced through the distillation of fermented sugarcane must, in a process divided into three stages: the head fraction, the heart fraction, and the tail fraction. The head and tail fractions are discarded, often directed towards ethanol production. This historical context reflects the importance of sugarcane in the Brazilian economy, being one of the first globalized industries. The main components of cachaça are water and ethanol, but it also contains other elements that influence its flavor and aroma, such as heterocyclic compounds. Studies have shown that cachaça and its head fraction can be used as solvents in industrial syntheses, highlighting their economic and environmental potential. Heterocyclic compounds, which contain heteroatoms in the carbon chain, are relevant in organic chemistry and in the research of new pharmaceuticals. The objective of this work was to produce compounds such as 1,4-dihydropyridine, 3,4-dihydropyrimidinone, and hexahydroquinoline using different solvents: absolute ethanol, acetonitrile (conventional solvents), and head fraction of cachaça and cachaça (alternative solvents). The use of bismuth nitrate pentahydrate as a catalyst was also investigated. Syntheses were conducted through multicomponent reactions (MCRs), where the reagents were mixed in a single reaction flask with the solvent and catalyst under reflux. The reagents used included aromatic aldehyde, ethyl acetoacetate, and ammonium acetate for 1,4-dihydropyridine; aromatic aldehyde, ethyl acetoacetate, cyclohexanone, and ammonium acetate for hexahydroquinoline; and aromatic aldehyde, ethyl acetoacetate, and urea for 3,4-dihydropyrimidinone. Product characterization was performed using differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy (1H and 13C NMR), and Fourier-transform infrared spectroscopy (FTIR). The results showed that the syntheses using head fraction of cachaça and cachaça as solvents were successful, evidenced by the presence of precipitates and satisfactory characterization results. The optimized methodology favored the production of hexahydroquinoline with better yields. It was noted that yields obtained with alternative solvents surpassed those with conventional solvents. The use of 0.4% bismuth nitrate pentahydrate as a catalyst proved effective. The head fraction of cachaça stood out as an environmentally advantageous alternative, offering yields superior to ethanol. Although there is still room for research on the optimal conditions for these reactions, the results indicate that components of cachaça directly influence the yield of MCRs, demonstrating its potential in the chemical industry. The potential use of cachaça and its head fraction as an alternative solvent in organic syntheses in Brazil, where sugarcane production accounts for 45.72% of global output, not only reduces costs by replacing absolute ethanol but also promotes positive social and economic impacts, enhancing local culture and utilizing a frequently discarded byproduct, thereby strengthening communities and sustainable practices.