Nano-TiCl2/cellulose: an eco-friendly bio-based catalyst for one-pot synthesis of 4H-pyrimido[2,1-b]benzothiazole derivatives

摘要

Cellulose is among the most abundant natural carbon-based biopolymers containing free OH groups with nucleophilic character for bonding to Lewis acids such as TiCl4. Nano-TiCl2/cellulose as a bio-based and eco-friendly Lewis acid catalyst was prepared via reaction of nano-cellulose and TiCl4 in dichloromethane as solvent under room temperature conditions. This catalyst has been characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, powder X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray fluorescence techniques, and transmission electron microscopy. Nano-TiCl2/cellulose has been shown to effectively promote multi-component synthesis of 4H-pyrimido[2,1-b]benzothiazole derivatives by reaction of aldehydes, beta-ketoester, and 2-amino benzothiazole under thermal conditions in polyethylene glycol 400 as solvent. Simple methodology,an eco-friendly catalyst, a clean procedure, easy work-up, and excellent yields are some of the important advantages of this protocol.