A novel and efficient synthesis of benzo[f]isoindole-4,9-diones through the I₂-promoted cyclization reaction of N-substituted amino acid esters and quinones has been realized successfully via an unprecedented 1,3-dipolar cycloaddition using KF as the base. Different substituted amino esters were found able to react with quinones through a cycloaddition reaction to afford 2-substituted benzo[f]isoindole-4,9-diones. The unexpected, short, attractive and direct synthesis of these interesting compounds is important and relevant, and provides an extremely preferable method for the synthesis of 2-substituted benzo[f]isoindole-4,9-diones.