Visible light-induced organophotoredox-catalyzed difunctionalization of alkenes and alkynes

In the era of organic synthesis, the direct difunctionalization strategies of alkenes and alkynes are very eminent, which open up an excellent route to introduce two functional groups simultaneously. At the same time, photocatalysis has become an imperative tool in organic synthesis due to its activation potential along with their environmentally benign nature. Moreover, the employment of photoredox catalysis in the di-functionalization strategy has become a step ahead toward sustainability, specifically when the photoredox catalyst is metal-free. In this review, realizing tremendous important trend, we have specifically tried to assemble several reported difunctionalization strategies of alkynes and alkenes using metal-free dye-based photoredox catalysts. This perspective showed the use of eosin Y, 4CzIPN, Rose Bengal, Mythylene Blue, rhodamine B, Ph-PTZ, etc., as the most used organophotoredox catalysts. Furthermore, a detailed discussion of the mechanistic pathway is given in every scheme to depict a clear perspective of photoredox catalysts.