Formation of 3‑Alkynylidenephthalides\nby Gold(I)-Catalyzed\nAlkynylative Cyclization of <i>o</i>‑Alkynylbenzoic\nAcids under Visible Light Irradiation

Herein,\nwe report a Csp<sup>2</sup>–Csp cross-coupling\nprocess\ninvolving the merger of gold catalysis and visible light photocatalysis\nleading to the alkynylative cyclization of <i>o</i>-alkynyl\nbenzoic acids. The corresponding and previously undescribed alkynylidenephthalide\nproducts were obtained as mixtures of <i>E</i>:<i>Z</i> isomers. The key C–C bond formation is based on the photoactivation\nof the oxidative addition of an alkynyliodide to a vinylgold(I) intermediate\nresulting from an initial 5-<i>exo</i>-dig cyclization pathway,\nas supported by mechanistic studies including DFT calculations.