Optimization study and application of box-behnken model for probing eggshell supported transition metals based catalysts to synthesize hydrazone & dihydropyrimidinones

Solid supported catalysts have several synthetic applications. Herein, finely ground eggshells were used as a solid support for the preparation of transition metal (Ni, Zn, Cu, Sn and Co) based catalysts to synthesize 2,4-dinitrophenylhydrazone (3) and dihydropyrimidinones (7 and 8). The effect of catalyst load, time and temperature on product yield was studied. Box Behnken Model was employed, and three predictors named catalyst amount (A), reaction time (B), and reaction temperature (C) were used to find the correlation of the predictors with the yield. Second order polynomial equation was used to estimate the effects of these factors. According to the statistical model, about 12% increase in yield was observed as a result of one-unit increase in reaction time while all other terms were kept constant. The values of S (18.1616) and R² (71.2%) indicate that the statistical model gave an adequate fit to data. Quadratic model for the response surface was used for the analysis of variance (ANOVA) results, the larger F-values, and smaller p-values indicated that the predictors are in good agreement. The linear model terms of predictors were found to be significantly effective for yield (P < 0.05). The response surface and contour plots were also in agreement with the predicted model.