NaHSO<sub>4</sub>–SiO<sub>2</sub>-catalyzed aza-Diels–Alder reaction of <i>o</i>-hydroxybenzaldimines with 2,3-dihydrofuran: Diastereoselective synthesis of furanobenzopyrans

<p>NaHSO<sub>4</sub> supported on silica gel catalyzes the aza-Diels–Alder reaction of <i>o</i>-hydroxybenzaldimines with 2,3-dihydrofuran to provide furanobenzopyrans in reasonable yields and diastereoselectivity. The catalyst is recyclable and reusable up to two times without a significant loss of activity.</p>