Synthesis of naphthoxazinone derivatives using silica-bonded S-sulfonic acid as catalyst under solvent-free conditions

Silica-bonded S-sulfonic acid is employed as a recyclable catalyst for the synthesis of naphthoxazinone derivatives from the reaction of ß-naphthol, aromatic aldehydes and urea at 150°C under solvent-free conditions. The heterogeneous catalyst was recycled for five runs after the reaction of ß-naphthol, benzaldehyde and urea without losing its catalytic activity.