Role of calcinations and basicity of hydrotalcite as catalyst for environmental benign novel synthesis of 4H-pyrimido[2,1-b][1,3]benzothiazole derivatives of curcumin

A simple, efficient and step-economy synthesis to afford the library of 4H-pyrimido[2,1-b][1,3]benzothiazole derivatives of curcumin (4a-4h) from readily available substrates curcumin (potential biological molecule), 2-amino benzothiazole (biological active) and substituted aromatic aldehydes using novel heterogeneous calcined Mg-Al-CO3 hydrotalcite under solvent free conditions is described. The calcined hydrotalcite with an Mg/Al ratio of 3 : 1 derived from calcinations at 750 K was found to be a suitable catalyst that gives the highest basicity and the best catalytic activity for this reaction. The catalysts were characterized with XRD and SEM and Hammett titration method. This protocol has several advantages such as easy to work up, high activity of catalyst and reusability.