A one-pot three component reaction mediated by lemon juice in an aqueous medium for the synthesis of diverse pharmaceutically important tricyclic fused imidazoles tethered with aryl and various cyclic 1,3-dicarbonyls has been reported. The reaction of arylglyoxals with cyclic 1,3-diacarbonyls such as N-methyl-4-hydroxyquinolone, 2,4-dihydroxyquinoline, 4-hydroxycoumarin or 4-hydroxy-6-methyl-2-pyrone with various 1,3-N,N-binucleophiles such as 2-aminobenzothiazoles or 2-aminobenzimidazoles provided medicinally important diverse tricyclic fused imidazoles having aryl and cyclic 1,3-dicarbonyl substituents under metal-free conditions. This method is a natural acid catalyzed multicomponent reaction in an aqueous medium for the synthesis of diverse tricyclic fused imidazoles in good to excellent yields.