brønsted acidic ionic liquid as the efficient and reusable catalyst for synthesis of coumarins via pechmann condensation under solvent-free conditions

a mild and efficient method has been developed for the preparation of substituted coumarins from reaction of various phenols with different β-ketoesters via pechmann condensation in the presence of brønsted acidic ionic liquid (n-(4-sulfonic acid) butyl triethylammonium hydrogen sulfate) as an effective catalyst under solvent-free conditions. different phenols reacted with ethyl acetoacetate to produce the corresponding substituted coumarins in high to excellent yields and short reaction times. moreover, [tebsa][hso4] has been used as an effective green catalyst for the synthesis of coumarin derivatives under solvent-free conditions. using the relatively non-toxic (halogen-free) and reusable brønsted acidic ionic liquid, high catalytic efficiency, high yields, short reaction times and straightforward work-up are advantages of this protocol.