Synthesis of 1,2,3,4-Tetrahydroquinolines Using AlCl₃in Aqua Mediated

Abstract

Catalytic performance of Lewis acids have been investigated in the synthesis of 1,2,3,4-tetrahydroquinolines via cyclocondensation reaction of aniline derivatives with cyclic enol ethers such as 3,4-dihydro-2H-pyran and 2,3-dihydrofuran. The catalytic activity of various of these catalysts in different solvents was compared with other classical catalysts such as KSF clay (1.5 g), InCl3 (10−20 mol%), ZrOCl2 (10 mol%), Sc(OTf)3 (3 mol%), PANI−InCl3 (10 mol%), I2 (20 mol%), InCl3 (5 mol%), 4-npa (25 mol%) and Cellulose−SO3H (0.03 g).

Progress in the Chemistry of Tetrahydroquinolines

“…335 As in the previous case, arylamines reacted with 1 equiv of the enol ethers to give the corresponding N-arylimines, which then underwent a formal [4+2] cycloaddition with another equivalent of the enol ether in the presence of TBPA •+ to afford tetrahydroquinolines as a diastereomeric mixture. Other catalytic systems, including nanoporous aluminosilicate, 336 cellulose−SO 3 H, 337 AlCl 3 /H 2 O, 338 Sm(NO 3 ) 3 , 339 and lanthanide halides, 340 also effectively catalyzed the ABB′ threecomponent reaction between arylamines and cyclic enol ethers.…”

Novel N‐allyl/propargyl tetrahydroquinolines: Synthesis via Three‐component Cationic Imino Diels–Alder Reaction, Binding Prediction, and Evaluation as Cholinesterase Inhibitors

“…However, imino Diels–Alder reaction between aldimines and electron‐rich alkenes is probably the most powerful synthetic tool for the construction of these type of heterocyclic compounds . Diverse Lewis and Brønsted acids have been used as efficient catalysts for the synthesis of tetrahydroquinolines . When substituted anilines and formaldehyde are used as starting materials, a cationic 2‐azadiene intermediate is generated in situ .…”

AlCl3-Promoted Thiocyanation of N-Containing Aromatic and Heteroaromatic Compounds Under Solvent-Free Conditions

“…It has been extensively used as a strong Lewis acid in many organic reactions such as Friedel-Crafts reactions and Fries rearrangement. 16,17 Recently, AlCl 3 has been employed for some other transformations such as the synthesis of 5-benzoylacenaphthene, 18 selective synthesis of 2-aryl-2H-and 4-aryl-4H-3,5-diformylpyrans, 19 asymmetric aldehydes arylation, 20 1,4-dihydropyridines synthesis, 21 cycloadditions of activated cyclopropanes and aromatic aldehydes, 22 1,2,3,4-tetrahydroquinolines synthesis, 23 and substituted guanidines synthesis. 24 In continuation of research interest on thiocyanation of N-containing (hetero)aromatic organics, 25 herein we report AlCl 3 as a commercially available and low-cost promoter for thiocyanation of some N-containing heteroaromatics and N-activated arenes in the presence of NH 4 SCN at room temperature under solvent-free conditions (Scheme 1 and Table 2).…”