Organocatalytic visible light induced S-S bond formation for oxidative coupling of thiols to disulfides

In this work, we developed a visible light induced oxidative coupling of thiols into the corresponding disulfides in a process catalyzed by an inexpensive and non hazardous Rose Bengal dye. Our optimization study revealed that the use of Rose Bengal catalyst under irradiation with visible light in either 2-propanol or water at room temperature can convert a variety of thiols into their corresponding disulfides in good to excellent yields. Natural sunlight can be applied as a light source to prepare disulfide in high yield at gram-scale quantity. Our photochemical reaction can be performed in a continuous flow reactor, demonstrating a short residence time. The key benefits of this reaction include the use of metal-free, low cost Rose Bengal catalyst and practical operation (room temperature, open flask, undried solvents and simple work up procedure by extraction).