| Abstract: |
The transition away from volatile, petroleum-derived organic solvents remains one of the most consequential shifts within contemporary synthetic chemistry, and catalytic methodologies built around green reaction media now occupy a central place in that transition. This review consolidates a decade of published work on deep eutectic solvents, ionic liquids, water, supercritical carbon dioxide, bio-based solvents, and solvent-free mechanochemical routes, examining how each medium interacts with catalytic systems ranging from organocatalysts and metal nanoparticles to immobilized enzymes. Rather than cataloguing individual reactions, the analysis draws together reported yields, E-factors, catalyst recyclability, and reaction-time data across roughly ninety primary sources to identify where green-solvent catalysis genuinely improves on conventional practice and where the improvement is more modest than the literature's framing suggests. Deep eutectic solvents and solvent-free protocols emerge as the most consistently favourable in terms of atom economy and waste reduction, while ionic liquids and supercritical fluids show strong performance metrics but weaker evidence of industrial scalability. The review also surfaces recurring methodological gaps: inconsistent green-metric reporting, limited life-cycle assessment, and sparse data on solvent toxicity to living systems. These gaps, more than any inherent limitation of the chemistry itself, constrain confident claims about sustainability. The paper closes by outlining research directions capable of closing this evidence gap, including standardized metric reporting and computational solvent-selection frameworks. |
