Photo-induced transition-metal and external photosensitizer-free organic reactions

Abstract

Currently, photoreactions have become powerful synthetic tools with a broad scope of application. However, many photoreactions require the addition of transition-metal catalysts (Ni, Cu and so on) and photosensitizers (Ir and Ru complexes, and organic photosensitizers) to promote the transformation, which challenges metal sustainability and complicates product purification. The development of transition-metal and photosensitizer-free photoreactions could not only reduce the production costs but also contribute to sustainable development. Moreover, studies of the excited state of light-absorbing substances will provide powerful knowledge for designing new green and efficient photoreactions without resorting to external photosensitizers. This review mainly focuses on photoreactions in the absence of transition-metals and photosensitizers, and highlights the mechanisms of such reactions.