Cu2O Nanocrystals-Catalyzed Photoredox Sonogashira Coupling of Terminal Alkynes and Arylhalides Enhanced by CO2

Herein the first visible-light-activated Sonogashira C-C coupling reaction at room temperature catalyzed by single-metal heterogeneous Cu2O truncated nanocubes (Cu2O TNCs) was developed. A wide variety of aryl halides and terminal alkynes worked well in this recyclable heterogeneous photochemical process to form the corresponding Sonogashira C-C coupling products in good yields. Mechanistic control studies indicated that CO2 enhances the formation of light-absorbing heterogeneous surface-bound Cu-I-phenylacetylide (lambda(max)=472 nm), which further undergoes single-electron transfer with aryl iodides/bromides to enable Sonogashira Csp2-C-sp bond formation. In contrast to literature-reported bimetallic TiO2-containing nanoparticles as photocatalyst, this work avoided the need of cocatalysis by TiO2. Single-metal Cu-I in Cu2O TNCs was solely responsible for the observed Csp2-C-sp coupling reactions under CO2 atmosphere.