“…Various homogeneous and heterogeneous acid catalysts, including SnCl 2 , SbCl 3 doped on hydroxyapatite (SbCl 3 ‐HPA), tungstophosphoric acid supported on nanosized MCM‐41 (TPA/MCM‐41), perchloric acid adsorbed on silica gel (HClO 4 ‐SiO 2 ), GdCl 3 , and ferric sulfate, have been reported for the synthesis of tetrahydropyranoquinolines. However, some of the methods used so far suffer from limitations such as the use of large amounts of catalyst (up to 50 mol‐%), very low diastereoselectivities, or poor catalyst reusability.…”