%0 Journal Article
%T Kinetic and Mechanistic Investigation of Pyrano[2,3-d]pyrimidine Formation in the Presence of Catalyst under Novel One-Pot Three-Component Reaction
%A Sayyed Mostafa Habibi-Khorassani
%A Malek Taher Maghsoodlou
%A Mehdi Shahraki
%A Sadegh Talaiefar
%A Jasem Aboonajmi
%J Organic Chemistry International
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/210327
%X 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, ¦¤G£¿, ¦¤S£¿, and ¦¤H£¿) 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. 1. Introduction Multicomponent reactions (MCRs) involving pot, atom, and step-economy have received substantial consideration from the organic community due to their advantages over conventional multistep synthesis [1¨C6]. This kind of reactions have some advantages over conventional linear syntheses, including shorter reaction times, lower costs, high atom-economy, energy saving, the possibility for combinatorial surveying of structural variations, and environmental friendliness. The benzopyrans and their derivatives, in particular, have shown several biological and pharmacological properties, such as spasmolytic, diuretic, antianaphylactin, antisterility, and anticancer agents [7¨C10]. The polyfunctionalized benzopyrans were used as cosmetics, pigments, and biodegradable agrochemicals [11, 12]. Due to their applications, the syntheses of heterocyclic derivatives of these ring systems have great importance in medicinal chemistry and organic synthesis. Strategies for the synthesis of these compounds have varied from one-pot to multistep approaches [13]. In recent years, the syntheses of pyrano[2,3-d]pyrimidine were reported using a plethora of reagents in the presence of catalyst, such as L-proline [14], microwave irradiation [15], H6P2W18O62¡¤18H2O [16], 4-(dimethylamino) pyridine (DMAP) [17], and diammonium hydrogen phosphate [18]. However, some of these
%U http://www.hindawi.com/journals/oci/2014/210327/