Friedel–Crafts alkylation of 4-hydroxycoumarin catalyzed by sulfonic-acid-functionalized pyridinium chloride as a new ionic liquid

A green, simple and efficient synthesis of bis-coumarin derivatives via the condensation of 4-hydroxycoumarin with arylaldehydes using sulfonic-acid-functionalized pyridinium chloride {[Pyridine–SO3H]Cl} as a new, homogeneous and reusable catalyst and ionic liquid is reported.

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