Light-induced Regioselective 6-endo versus 5-exo Cycloisomerization of o-Alkynylbenzoic Acids

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