One pot three-component imino Diels–Alder reactions of various types of aldehydes, aniline and dihydropyrane were studied in the presence of nano sized MCM-41 supported 12-tungstophosphoric acid (TPA) as solid acid catalyst. MCM-41 as solid support was synthesized in nano size and the catalysts with different loading amounts of TPA (5–30 wt%) were prepared and characterized by XRD, FT-IR and SEM techniques. The results confirm a good dispersion of the heteropoly acid on the solid supports and based on the experimental results, the catalyst with 10 wt% heteropoly acid shows the best catalytic activity using 0.5 mol% heteropoly acid relative to the aldehyde. The recovery experiments show that the catalyst is reusable after calcination without significant loss in its activity.
Jacquemond-Collet, I, Benoit-Vical, F, Mustofa, V, Valentin, A, Stanislas, E, Mallié, M, Fourasté, I (2002) Planta Med68:68.