During formylation of 2-quinolones by DMF/Et3N mixture, the unexpected 3,3'-methylenebis (4-hydroxyquinolin-2 (1H) -ones) were formed . The discussed mechanism was proved as due to the formation of 4-formyl-2-quinolone as intermediate . Reaction of the latter compound with the parent quinolone under the same reaction condition gave also the same product . The structure of the obtained products was elucidated via NMR, IR and mass spectra . X-ray structure analysis proved the anti-form of the obtained compounds, which were stabilized by the formation hydrogen bond . Molecular docking calculations showed that most of the synthesized compounds possessed good binding affinity to the SARS-CoV-2 main protease (Mpro) in comparable to Darunavir.