Synthesis of 7-hydroxy-4-methylcoumarin via the Pechmann reaction with Amberlyst ion-exchange resins as catalysts

The Pechmann reaction of resorcinol with ethyl acetoacetate over various Amberlyst-type catalysts under mild reaction conditions in short reaction times resulted in high yields of 7-hydroxy-4-methylcoumarin. For purposes of comparison, other solid acid catalysts were also investigated. The best-performing material was Amberlyst-S, with 95% conversion and 98% selectivity in refluxing toluene after 2 h of reaction time at 120 °C. The materials could be regenerated and recycled.