Graphene Oxide Substituted Diethylenetriamine and Silica Nanocomposite as a Novel, Efficient and Sustainable Catalyst for the Synthesis of Pyrimido[2,1-b]Benzothiazoles

This work reports the efficient synthesis of Pyrimido[2,1-b]benzothiazoles using a novel diethylenetriamine-functionalized graphene oxide and silica nanocomposite. Graphene oxide was first modified with diethylenetriamine followed by treatment with triethylortosilicate in acetic acid and water to achieve the final nanocomposite. The nanocomposite was characterized by FT-IR, XRD, FE-SEM, EDS, and TGA techniques. The synthesis of pyrimido[2,1-b]benzothiazoles proceeded through a one-pot three-component reaction under solvent-free conditions. Optimized conditions for 4-chlorobenzaldehyde derivative involves solvent-free medium, 0.02 g of catalyst at 80°C for 30 min which resulted in 95% yield. The nanocomposite was found to be environmentally friendly, stable under the reaction conditions, easily recoverable, inexpensive, non-metal, safe handling, and reusable for the synthesis of the pyrimido[2,1-b]benzothiazoles at least five times. The presented procedure and nanocomposite were more sustainable and efficient than the previously published reports.