Visible-light-driven alkynylation: a sustainable approach to rigid molecular architectures.

Alkynes are indispensable molecular motifs in organic, materials, medicinal, and pharmaceutical chemistry, owing to their linear geometry, structural rigidity, distinctive reactivity, and widespread occurrence in bioactive molecules and bioorthogonal platforms. Conventional alkyne synthesis, such as Sonogashira and Glaser couplings, and metal acetylide-based methods, often require harsh conditions such as toxic metal catalysts, strong bases/oxidants, and elevated temperatures, while classical radical approaches typically rely on high-energy UV irradiation, leading to poor selectivity and limited functional group tolerance. In this context, visible-light-mediated photoredox catalysis has emerged as a mild, sustainable, and highly tunable platform for alkynylation reactions. This review elucidates the dynamic landscape in visible-light-mediated alkynylation from 2021 to 2025, critically analysing alkynyl precursor reactivity, radical intermediates, and the mechanistic intricacies of the single-electron-transfer processes that govern these transformations. Thus, it establishes a cohesive conceptual framework that rationalizes catalyst selection, highlights key reaction design principles, and underscores the interplay between radical reactivity and single-electron-transfer processes for the rational development of next-generation, site-selective alkynylation strategies. A comprehensive analysis of emerging strategies, existing limitations, and opportunities for future development is presented in this review.