The synthesis of 3-(aryl(piperidin-1-yl)methyl)-4-hydroxyquinolin-2(1H)-one derivatives
via catalyst-free multicomponent reaction is described. The reaction of 4-hydroxyquinolin-2(1H)-one,
piperidine, and 4-chlorobenzaldehyde was carried out in different solvents and under solvent-free conditions
at room temperature. The best solvent in terms of the yield and reaction time was found to be
dichloromethane. Most substituted benzaldehydes reacted with 4-hydroxyquinolin-2(1H)-one and
piperidine to afford corresponding products in good-to-excellent yields. Aldehydes with electronwithdrawing
groups were more reactive to exhibit higher reaction rates. However, 2-substituted benzaldehydes
did not react with 4-hydroxyquinolin-2(1H)-one and piperidine under the reaction condition.
Aldehydes bearing a hydroxyl group failed to produce the corresponding products.
Catalyst- and solvent-free approach to 2-arylated quinolines via [5 + 1] annulation of 2-methylquinolines with diynones