Various 2-phenyl-4H-chromeno(3,4-d)thiazol-4-one derivatives have been synthesized through C–H bond activation using sodium sulfide as a source of sulfur atoms and by employing I₂ as a catalyst and H₂O₂ as the terminal oxidant. Transition metal-free oxidative coupling for the formation of C–S bonds is one of the salient features of the present protocol. A number of thiazole containing coumarin derivatives having various substituents has been accomplished in good yields.