A green and efficient one pot three component protocol has been developed for the synthesis of naphthopyranopyrimidines, diazaanthra[2,3-d][1,3]dioxole-7,9-dione and tetrahydrobenzo[a]xanthen-11-ones in PEG-400 catalyzed by alum (KAl(SO₄)₂·12H₂O). Single crystal X-ray diffraction studies have been performed for naphthopyranopyrimidine (5). The synthesized compounds were screened for in vitro antioxidant activity by DPPH scavenging assay and compounds 3 and 4 manifested profound antioxidant potential.