Highly efficient solvent-free synthesis of quinazolin-4(3H)-ones and 2,3-dihydroquinazolin-4(1H)-ones using tetrabutylammonium bromide as novel ionic liquid catalyst

A simple and efficient procedure for the synthesis of 2-arylquinazolin-4(3H)-ones has been developed through cyclocondensation of 2-aminobenzamide with aromatic aldehydes using tetrabutylammonium bromide (TBAB) as novel neutral ionic liquid catalyst in the presence of copper (II) chloride (CuCl2) as oxidizing agent under solvent-free conditions at 100 °C. In the absence of CuCl2 and under a nitrogen atmosphere, the unoxidized intermediates, 2-aryl-2,3-dihydroquinazolin-4(1H)-ones, were isolated. Treatment of these intermediates with CuCl2 in TBAB media gave the oxidized products 2-arylquinazolin-4(3H)-ones. On the other hand, cyclocondensation of 2-aminobenzamide with aromatic aldehydes in TBAB under microwave irradiation directly gave 2-arylquinazolin-4(3H)-ones.