Search

• Sonogashira-type coupling reactions under Cu-, ligand- and base-free reaction conditions. • Use of nanoparticles effects. • Steric effects results regioselectivity. • Use of hydrophobic effects (surfactants, polymers). • Recyclability of catalyst. • Sustainable organic transformations towards green protocols. A large number of publications yearly witnessed myriad synthetic uses of the Sonogashira-Hagihara cross-coupling in organic transformations. Still, many challenges need to be addressed for example, readily available aryl chlorides gave moderate yields, deactivated aryl bromides required harsh reaction conditions, ortho -substituted aryl halides, bulky and nitrogen-containing aryl halides (substituted pyridines) and aliphatic alkynes afford poor yields in a longer reaction time. Pd-catalysts-recycling is necessary but impossible in homogenous catalysis and the catalytic activity gradually decreased because of the Pd-species leaching. Heterogeneous catalysis is successful but has tiresome catalyst separation. Phase-transfer catalysis is not much used because of the recycling of surfactant catalyst is difficult. Phosphine-based ligands are sensitive to air and moisture so limits its uses. Nitrogen-donor ligands have received much attention due to more stable nature but quite costly. Therefore, we need to develop the ligand-free Pd-catalysts might be practically a viable alternative. N-heterocylic carbenes (NHCs) catalysts are costly and have short shelf-life. The palladacycle catalysts gave high turnover numbers but not used in large-scale synthesis due to the insolubility. Use of dendrimers slowed the reaction rate due to formation of polymer or oligomer as byproduct which deposited on the catalyst surface. Ionic liquids and photocatalysts (microwave or UV-visible) are not used extensively due to accumulation of alkyne hydrogenation product on the catalyst surface. Bimetallic nanomaterials as catalyst are useful but underdeveloped. Metals-free Sonogashira reactions are economical and eco-friendly but less reported. It showed that ligands should be air and moisture stable at room temperature, stored for unlimited shelf-life, exhibit high turnover numbers and high rate of reaction. In this review, a recent advances and emerging opportunities for easy preparation of stable Pd-based catalysts, their intrinsic mechanistic and potentials for Sonogashira-type reactions under sustainable, open-air and Cu-, ligand-, solvent- and amine-free conditions were discussed, covering literature up to 2024. The review would be helpful in the research and development of new and modified Sonogashira-type reactions for the synthetic applications in the future. The review highlights the origin, emerging trends in the mechanistic insights and recent advances towards green protocols of Sonogashira-type coupling reaction under Cu-, ligand- and base-free reaction conditions. [Display omitted] [ABSTRACT FROM AUTHOR]