Abstract
Fe(ClO4)3 and silica gel adsorbed Fe(ClO4)3 are reported as catalysts for [4+2] cycloaddition reactions of imines (formed in situ from anilines and enol ethers) with cyclic enol ethers to afford the corresponding pyrano- and furano[3,2-c]quinolines in good to excellent yields. Also, the catalytic activity of Fe(ClO4)3 in different solvents was compared with the other iron catalysts such as FePO4, Fe2(SO4)3.XH2O, (NH4)Fe(SO4)2.12H2O, Fe(acac)3, Fe(DS)3, Fe(OH)3, FeCl3.6H2O, and Fe(NO3)3.9H2O.