Kinetic and Mechanistic Investigation of Pyrano[2,3-d]pyrimidine Formation in the Presence of Catalyst under Novel One-Pot Three-Component Reaction

Sodium acetate was applied as an efficient catalyst for the one-pot, three-component condensation reactions consisting of 4-nitrobenzaldehyde 2, malononitrile 3, and thiobarbituric acid 1. Use of nontoxic reaction components, short reaction times, environmental, easy work-up, and high yields are some remarkable advantages of this method. Kinetics and mechanism of the reaction were spectrally studied and the second order rate constant (kovr = k1) was automatically calculated by the standard equations contained within the program. The second order rate constant [Ln(kovr = k1), Ln(kovr = k1)/T] that depended on reciprocal temperature was in good agreement with the Arrhenius and Eyring equations, respectively. This data provided the suitable plots for calculating the activation energy and parameters (Ea, ΔG‡, ΔS‡, and ΔH‡) of the reaction. Furthermore, from studying the effects of solvent, concentration, and catalyst on the reaction rate, useful information was obtained regarding the mechanism. The results showed that the first step of the reaction mechanism is a rate determining step (RDS). The proposed mechanism was confirmed in accordance with the experimental data and also the steady state approximation.