Síntese multicomponente de 3,4-Diidropirimidin-2(1H)-ona catalisada por Bi(NO3)3∙5H2O

Abstract

The conventional synthesis is composed of several steps to prepare the final product. These steps generate waste, increase the reaction time and increase the energy cost. On the other hand the multicomponent reactions (MCR) can be done in one step and in just one flask. The MCR is characterized for the mixture of three or more reagents in a flask, and it can be aided by catalysis. However, despite their advantages, MCR sues much time and makes use of excess organic solvents in some cases. In order to remedy this disadvantage, heterogeneous catalysts in nanometre scale can be used, and also other types of Lewis acid. The homogeneous catalysis provides even more contact between reagent and catalyst, being able to be removed easily , as in the case of some Lewis acids. An important catalyst is bismuth (III) nitrate due to it’s extensive application in catalytic processes and it's easy obtainment at low cost. The objective of this work was to carry out the Biginelli synthesis through homogeneous catalysis, using a catalyst that are easy to obtain and less harmful to the environment. The yields of 3,4-diidropirimidinona (DHPM) synthesis were evaluated using bismuth (III) nitrate ( Bi(NO3)3 ∙ 5H2O) as catalyst. The product was obtained from a mixture of benzaldehyde (5 mmol), B-ketoester (5 mmol), Urea (6 mmol) and Ethanol (5 mL) with different concentrations of catalyst. Bi(NO3)3 ∙ 5H2O catalyzed the formation of DHPM in different yields, reaching a maximum of 77,14% when using 9,24% of the catalyst. After the crystallization of the product, the Bi(NO3)3 ∙ 5H2O was separated in the vacuum filtration process. The structural characterization of the product was performed by 1H NMR (600 MHz) and FTIR, confirming the formation of DHPM. The results showed that the reaction presents specific conditions of higher yield, and allowed the proposal of the reaction mechanism. Although there is still much to research about the best conditions for this reaction, it became clear that bismuth (III) nitrate has a direct influence on the yield of this MCR.