Efficient synthesis and biological evaluation of new benzopyran-annulated pyrano[2,3-c]pyrazole derivatives

A one-pot method has been described to synthesize benzopyran-annulated pyrano[2,3-c]pyrazoles, effectively by combining O-alkenyloxy/alkynyloxy-acetophenones with various pyrazolones in triethylammonium acetate (TEAA) under microwave irradiation. While combination of O-allyloxy- or O-prenyloxy-acetophenones with pyrazolones occurred efficiently, that of O-propargyloxy-acetophenones was found effective in the presence of ZnO catalyst, via a domino Knoevenagel-hetero-Diels-Alder (DKHDA) reaction. Aminobenzopyran frameworks were also synthesized, after nitro-containing products were reduced in tandem with iron(II) in an acidic medium. The in vitro antiproliferative activity of these compounds was measured and discussed against gram-positive, gram-negative and M. tuberculosis bacteria, fungi, and various representative human solid tumor cell lines, in addition to their ferric reducing antioxidant capability.