Synthetic coumarins were prepared in high yields using ionic liquids as an environmental friendly alternative. 3,4-Dimethyl-7-hydroxycoumarin (3ab) and 3-isopropyl-4-methyl-5,7-dihydroxycoumarin (3bc) showed interesting activity against Taq DNA polymerase with IC₅₀ values of 115.7 μM and 82.2 μM, respectively. Also, 4-methyl-7-hydroxycoumarin (3aa) and 4-methyl-5,7-dihydroxycoumarin (3ba) exhibited inhibitory activity against MMLV-RT with IC₅₀ values of 23.5 μM and 18.3 μM, respectively. These inhibitors could have importance as antiretroviral chemotherapeutic agents and also for the development of antitumor drugs.