Unsaturated C2 synthons in photocatalysis: Taming and directing acetylene and ethylene in radical reactions

ABSTRACT The conversion of the simplest unsaturated C2 molecular building units (C 2 H 2 and C 2 H 4 ) to high-value-added fine chemicals has been a pivotal domain in modern synthetic chemistry. Because of the inherent inertness of both gaseous compounds, harsh reaction conditions are typically required to achieve π -bond selective transformations, barring their widespread applications in synthesis chemistry. Synthetic chemists have made considerable efforts to overcome these constraints through the development of specialized reactors, discovering novel catalytic systems, and devising innovative synthetic strategies. Recently, visible-light-induced photocatalysis has become the most welcomed platform for unsaturated C2 synthon diversity transformations thanks to its improved efficiency and selectivity under mild conditions. Furthermore, this catalytic mode revolutionizes the dilemma of classical photochemistry as well as radical chemistry for the diversity conversion of acetylene and ethylene. This review surveys recent advancements and breakthroughs in the visible light-promoted chemistry conversion of ethylene and acetylene, highlighting the role of photocatalysis as a driving force behind the significant changes in this area.