Two novel Br?nsted acidic ionic liquids 1-(4-sulfonic)-benzyl-3-methylimidazolium hydrogen sulfate (a) and 1-(4-sulfonic)-benzyl-3-methylpyridium hydrogen sulfate (b) were used as catalyst and medium in the one-pot synthesis of 3-substituted-4(3H)-quinazolinones, using anthranilic acid, triethyl orthoformate or formic acid and aromatic or aliphatic amines as starting materials under microwave irradiation. It was found that the reactions completed within 4～6 min with good to excellent yields (74～94%) in the presence of 10 mol% ionic liquids. The ionic liquids can be recovered easily and recycled three times without any significant loss in catalytic activity. This synthetic method has the advantage of generality. The aromatic or aliphatic substituents can be introduced in the 3-position, the substrates with electron-withdrawing substituents can also take part of the reaction smoothly and offered satisfactory yields. In addition to, this synthetic method can use 85% formic acid directly with yields of 72%～91%.

Key words: Br?nsted acid, ionic liquid, multi-component reaction, microwave, 4(3H)-quinazolinone