The synthesis of the 4H-pyrimido[2,1-b][1,3]benzothiazole (1a-1h), 1,2,4-triazoloquinazolines (2a,2b), octahydroquinazolinones (3a,3b) and fused thiazolo[2,3-b]quinazolinone (4a,4b) by multicomponent reactions using aldehydes, dicarbonyl and 2-amino benzothiazole/3-amino-1,2,4-triazole/urea/thiorea has been carried out in the presence of Mg-Al-CO 3 and Ca-Al-CO 3 hydrotalcite as a heterogeneous catalyst. Hydrotalcites need short reaction times, are non-toxic, easy to work up and reusable under solvent free conditions, hence making this process environment friendly. A detailed mechanistic study shows that the reaction using urea proceeds through imine intermediate 6. In addition, we have isolated and characterized the key intermediate of the reaction by using hydrotalcite.

No abstract