Olefin cyclization on Cu(111) driven by subsurface carbon and ultraviolet irradiation

Among several major unresolved challenges in reaction chemistry, controlling the yield and selectivity is particularly crucial. For on-surface synthesis (OSS), a prototype for basic understanding of reaction mechanisms, such control remains elusive. Here, using olefin cyclization, an important reaction in organic synthesis yet unknown for OSS to the best of our knowledge, as the model system, we propose a strategy to address this challenge by introducing carbon into the subsurface of Cu(111) (C-Cuδ+) and UV irradiation. The total olefin coupling rate on C-Cuδ+ increases to 10.1- and 5.3-fold higher than that on pristine Cu(111) at 298 and 323 K, respectively. The initial cyclization temperature reduces by 55 K on C-Cuδ+. UV irradiation further promotes the cyclization ratio from 22% to 40.3%. By integrating surface catalysis of the substrate with photochemistry of light-absorbing reactants, our results may open up a promising route for overcoming high reaction barriers and regulating selectivity in OSS.