Light-Induced Regioselective 6-Endo versus 5-Exo Cycloisomerization of o-Alkynylbenzoic Acids

Abstract Regioselectivity of the gold(I)-catalyzed cycloisomerization of o-alkynyl benzoic acids is significantly influenced by blue LEDs irradiation. In particular, the reaction exhibits higher selectivity toward the 6-endo regioisomer when irradiated with blue light, whereas the 5-exo product is obtained as the major product in the absence of light. These findings prompted mechanistic inquiries that we sought to address through running the reactions in diverse conditions and also by studying the reactivity of the vinylgold(I) complexes that are formed as intermediates.