Multifaceted reactivity of benzimidazoline as an electron donor, a hydride donor, and a catalyst

Organic hydrides are metal-free, sustainable reductants with broad structural diversity and tunable reactivity. Among them, 1,3-dimethylbenzimidazoline (BIH) stands out as one of the most potent C–H-based reducing agents. This review highlights the distinct properties of BIH that enable its versatile functionality as a hydride, electron, and hydrogen atom donor and summarizes its stoichiometric and catalytic applications in organic synthesis and CO₂ reduction. Recent advances in BIH regeneration strategies based on chemical, electrochemical, and photochemical methods are also discussed, emphasizing their relevance to sustainable catalysis. Particular attention has been paid to photochemical regeneration systems that enable visible light-driven catalytic cycles, including photosensitizer-free systems. These insights provide a foundation for the future development of BIH-based redox systems within green and efficient synthetic methodologies.