How Mechanical and Chemical Features Affect the Green Synthesis of 1H-Pyrazoles in a Ball Mill

This work investigated the chemical and mechanical factors that affect cyclocondensation reactions in a ball mill. Chemical characteristics such as the use or non-use of a catalyst, amount of catalyst and reactants, and product formation, as well as the yield and mechanical factors such as rotation frequency and the number, diameter, and material of the milling balls were evaluated. It was found that a rotation frequency of 450 rpm is efficient for energy transfer to the reactants because the conversion is higher at this rotation. The reaction was highly dependent on the time (3 min) and amount of p-TSA (p-toluenesulfonic acid) utilized as catalyst (10 mol 96). Five steel balls of 10 mm were considered to be the ideal number for the efficient mixing of the particles. For this work, the ideal conditions determined were used for the green synthesis of a series of 1H-pyrazoles.