From Technical Efficiency to Economic Efficiency: Development of Aza-Friedel–Crafts Reaction Using Phosphoric Acid Immobilized in Glycerol as a Sustainable Approach

The search for sustainable and practical synthetic methodology with high levels of technical efficiency is a highly topical subject that would contribute to developing recycling economy and saving resources. Green synthetic science has been firmly established and has provided essential design criteria for the development of a sustainable approach to high added value molecules and drug discovery, and the further development of sustainable manufacturing processes of medicines with new optimality principles for economic efficiency. In this study, a green atom economical aza-Friedel–Crafts reaction catalyzed by phosphoric acid immobilized in glycerol has been developed. This protocol provides a sustainable approach for the preparation of pyrrolyl and trifluoromethyl dihydrobenzoxazinones in excellent yields with remarkable features, such as bio-renewable glycerol as a cheap, safe and green solvent, easy product separation and catalytic system recycling under mild conditions. Furthermore, the preliminary biological activity of these products was evaluated in glioma (C6) and melanoma (B16BL6) tumor cell lines by using adriamycin as a positive control with the thiazoyl blue tetrazolium bromide (MTT) assay. The result suggests that product 5n shows promising cancer growth inhibition of glioma and melanoma, and is a promising lead compound for further investigation as anti-glioma and anti-melanoma agents.