Easy synthesis of polycyclic naphthopyran UV photoswitches using two one-pot reactions

Abstract An easy synthesis of complex naphthopyran molecules with fused pyrrole and 7 membered lactone systems, using just 3 reactions, including two cascade transformations, is described. These colorless molecules develop an intense red coloration once exposed to the UV or sunlight, at room temperature, returning spontaneously to the colorless state in less than 2 minutes. The incorporation of these photochromic molecules in polymeric matrices produced fast sunlight photoswitching materials operating at room temperature.