Solvent free synthesis of quinoxalines, dipyridophenazines and chalcones under microwave irradiation with sulfated Degussa titania as a novel solid acid catalyst

Sulfated TiO2–P25 (Degussa titania) has been prepared by sol–gel method using H2SO4 and characterized by FT-IR, XRD, FE-SEM, EDS, HR-TEM, XPS, DRS and BET surface area measurements. Sulfate loading by H2SO4 increases the Lewis acidity of Degussa tiatania. This catalyst gives an excellent yield with less reaction time and is an inexpensive and easily recyclable solid acid catalyst for the synthesis of quinaxalines, dipyridophenazines and chalcones under microwave irradiation.

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► TiO2–P25 possesses a unique type of surface involving both redox and acid–base site.
► TiO2–P25–SO42− has more acidic sites and so more efficient than bare TiO2–P25.
► Easy product isolation and catalyst reusability make this reaction eco-friendly.