La-Mg mixed oxide as a highly basic water resistant catalyst for utilization of CO2 in the synthesis of quinazoline-2,4(1H, 3H)-dione

The synthesis of quinazoline-2,4(1H, 3H)-dione was done by direct utilization of CO2 in the cyclization of 2-aminobenzonitrile (2-ABN) using lanthanum magnesia mixed oxide (La-Mg MO) as a strong basic catalyst under mild reaction conditions in water. It gave a conversion of similar to 92% with 100% selectivity at 140 degrees C in 14 h. La-Mg MO was prepared by hydrothermal method using urea as homogeneous precipitating agent. The catalyst was characterized by different analytical techniques like BET, XRD, FT-IR, SEM, and TGA, and the basicity by CO2-TPD and acidity by NH3 TPD. Various reaction parameters were studied to predict the reaction mechanism and kinetics. The reaction follows the Langmuir-Hinshelwood-Hougen-Watson (LHHW) type kinetics model with an apparent activation energy of 23.3 kcal mol(-1). The catalyst was recycled three times with an insignificant change in activity. The overall process is clean and green.