Metal-catalyzed alkene epoxidation: from traditional catalysts to sustainable cobalt-based systems

Alkene epoxidation is a cornerstone reaction in organic chemistry, enabling the synthesis of epoxides that are widely used as intermediates in pharmaceutical development, specialty chemicals, and industrial applications. This review offers a survey of metal-catalyzed strategies for alkene epoxidation. Conventional catalytic systems based on titanium, manganese, chromium, tungsten, and noble metals are examined in terms of their catalytic efficiency, selectivity, mechanistic pathways, and inherent drawbacks. Special attention is devoted to progress in cobalt-based catalysts, which have emerged as appealing alternatives owing to their cost-effectiveness, reduced environmental impact, and lower health concerns, and competitive catalytic activity. Collectively, this review highlights advances in catalyst development and process optimization, while also outlining the remaining challenges in achieving highly efficient, selective, and environmentally sustainable epoxidation methods suitable for large-scale use.