Imino Diels–Alder reactions: One-pot synthesis of tetrahydroquinolines

Progress in the Chemistry of Tetrahydroquinolines

“…The reaction between arylamines 645 , aryl aldehydes 646 , and cyclic vinyl ethers 647 in the presence of Brønsted acid catalysts, including HClO 4 –SiO 2 , HCl–EtOH, PANI–PTSA, and TPA/MCM-41, and cellulose sulfuric acid furnished the diastereomeric mixture of pyrano- or furano-tetrahydroquinoline derivatives 648 and 649 (Scheme , Table ). Although in all the cases excellent yields of the products were isolated, the diastereomeric ratio varied depending on the catalytic system.…”

“…Chandrasekhar and co-workers established a synthetic route for the construction of compound 643, in 13 steps, corresponding to the pentacyclic core of a family of structurally complex Melodinus alkaloids such as maloscine 644 through a CAN-catalyzed three-component Povarov reaction (Scheme 165). 301 302 HCl−EtOH, 303 PANI−PTSA, 304 and TPA/MCM-41, 305 and cellulose sulfuric acid 38 1).…”

Homogeneous and heterogeneous catalysts for multicomponent reactions

“…160 The most common method for preparing pyranoquinolines is by aza-Diels-Alder reaction of imines (derived from aromatic amines and aldehydes) with 3,4-dihydro-2H-pyran in the presence of Lewis acids such as GdCl 3 , 166 ZrCl 4 , 167 KHSO 4 168 etc. Recently, it has been reported that Brønsted and Lewis solid acids such as antimony chloride doped on hydroxyapatite (SbCl 3 -HAP), 169 perchloric acid adsorbed on silica gel (HClO 4 -SiO 2 ), 170 Fe 3+ -K10 Montmorillonite clay and HY zeolite 171 are highly efficient and diastereoselective solid acid catalysts for the one-pot synthesis of pyrano and furoquinolines by coupling the three components, benzaldehydes, anilines and 3,4-dihydro-2H-pyran or 3,4-dihydro-2H-furan. (Scheme 19).…”

Diastereoselective Synthesis of Pyranoquinolines on Zirconium‐Containing UiO‐66 Metal‐Organic Frameworks

“…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.…”