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Fructose was used as an efficient catalyst for three-component condensation reactions of aryl aldehydes,malononitrile,and dimedone in a mixture of EtOH and H_2O as green solvents.The advantages of this method are a short reaction time,high yields,low cost,easy accesses,and simple work-up.The mechanism of the synthesis of a derivative of 4H-tetrahydrobenzo[b]pyran was clarified using spectroscopic kinetic methods.The activation energy(Ea=65.34 kJ/mol)and related kinetic parameters(ΔG=69.14 kJ/mol,ΔS=20.99 J/(mol·K),andΔH=62.89 kJ/mol)were calculated,based on the effects of temperature,concentration,and solvent.The first step in the proposed mechanism was identified as the rate-determining step(k1),based on the steady-state approximation.
Fructose was used as an efficient catalyst for three-component condensation reactions of aryl aldehydes, malononitrile, and dimedone in a mixture of EtOH and H_2O as green solvents. The advantages of this method are a short reaction time, high yields, low cost, easy accesses, and simple work-up. The mechanism of the synthesis of a derivative of 4H-tetrahydrobenzo pyran was clarified using spectroscopic kinetic methods. The activation energy (Ea = 65.34 kJ / mol) and related kinetic parameters (ΔG = 69.14 ΔS = 20.99 J / (mol · K), and ΔH = 62.89 kJ / mol) were calculated, based on the effects of temperature, concentration, and solvent. first step in the proposed mechanism was identified as the rate- determining step (k1), based on the steady-state approximation.