An efficient approach to 16 examples of polyfunctionalized isochromeno[4,3-b]indol-5(1H)-one derivatives, obtained in 60-85% yield and with excellent regioselectivity, has been developed through a domino reaction of 2,2-dihydroxyindene-1,3-dione with aromatic amines under microwave irradiation. The atom- and step-economy and scope make this reaction a powerful tool for assembling polyheterocyclic scaffolds of general chemical and biomedical interest.