In continuation of our ongoing work for the synthesis of 7-Aminomethyl phthalides based fluorescent for the study of Cysteine-Specific Blue Fluorescence Probe , we developed a novel method for the synthesis of thioether 4 by a one-pot reaction by using the commercial available, trimethylsilyl iodide as a reagent in acetonitrile under reflux conditions, where it undergo multiple functional group changes, varies with mole equivalent of TMS-I used in the reaction The yield is low due to competitiveness between the phenyl sulfenyl radicals (to form dimer) and its reaction with phthalide-7-methylamine 3 to form thioether 4. Independently thioether 4