InCl3-Catalyzed Domino Reaction of Aromatic Amines with Cyclic Enol Ethers in Water: A Highly Efficient Synthesis of New 1,2,3,4-Tetrahydroquinoline Derivatives

The tetrahydroquinoline moiety is a structural feature of many natural products. By using a domino reaction of aromatic amines and cyclic enol ethers or 2-hydroxy cyclic ether catalyzed by indium chloride in water, various tetrahydroquinoline derivatives were synthesized efficiently. Most cyclization products showed cis selectivity. The use of 2,3-dihydrofuran as the cyclic enol ether provided both higher reactivity and cis selectivity than the use of 3,4-dihydro-2H-pyran. The cis selectivity was tentatively rationalized due to chelation control in water.