Metal-Free Cross-Coupling Reactions: Green Pathways for C–C Bond Formation

The growing concerns of rapid population expansion, depletion of fossil fuels, climate change, and escalating environmental degradation pose significant challenges to the sustainable development of modern society. In response, the scientific community has increasingly focused on the development of green and sustainable chemical methodologies. Within this context, metal-free synthetic strategies have gained prominence due to their ability to eliminate the dependence on toxic, heavy, and non-renewable transition metals. These methodologies offer a cleaner alternative for the chemo-selective transformation of inexpensive starting materials into high-value products. Recent advances have led to the development of metal-free oxidation, reduction, hydrogenation, and condensation reactions that align with the principles of green chemistry. However, the replacement of transition-metal-catalyzed carbon–carbon (C–C) bond-forming reactions remains a critical challenge. Innovative approaches involving the nucleophilic addition of organometallic species to carbonyl or imine compounds, as well as radical-mediated C–C couplings in the presence of aryl halides, are paving the way for sustainable alternatives. This abstract highlights the recent progress and ongoing efforts toward achieving environmentally benign synthetic methodologies, emphasizing the pivotal role of metal-free reactions in shaping a greener chemical future.