Reaction optimization. We initiated our study by employing ethyl 2-(phenylsulfonyl)acetate 1aa as a bifunctional reagent and but-1-yn-1-ylbenzene 2aa as the radical acceptor. To our delight, a promising 68% yield of the difunctionalized tetrasubstituted olefin 3aa was obtained using the organic fluorophore 1,2,3,5-Tetrakis (carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as the photocatalyst and K3PO4 as the base (Table , entry 1). Next, different photocatalyst including 2,4,6triphenylpyrylium tetrafluoroborate (TPT), Ru(bpy)3Cl2.6H2O, and [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 were tested, but none of them gave superior results (Table , entries 2-4). It is noteworthy that the choice of base had a significant impact on the reaction. A series of base screening finally led us to figure out that 2.0 equiv of K3PO4•3H2O provided the best yield of 89% for the product (Table , en tries 5-9). In addition, we also explored the solvent effect. However, neither DCE, THF nor DMF could further improve the reaction yield (Table , entry 10 and 11). Further control experiments revealed that the photocatalyst, light irradiation and K3PO4•3H2O were critical, as no desired product formation was observed in the absence of any of these parameters (Table , entry 12).