Understanding the Role of Base in Catalytic Transfer Hydrogenation: A Comparative Review
Batoul Taleb1, Assi Al Mousawi2, Ali Ghadban1,2
1Department of Chemistry and Biochemistry, Faculty of Sciences, Lebanese University, Beirut P.O. Box 6573/14, Lebanon.
Molecules (Basel, Switzerland)
|January 10, 2026
Summary
Catalytic transfer hydrogenation (CTH) offers a sustainable alternative to high-pressure hydrogen. This review compares base-assisted and base-free methods, highlighting factors influencing efficiency and selectivity in asymmetric synthesis.
Area of Science:
- Green Chemistry
- Organic Synthesis
- Catalysis
Background:
- Catalytic transfer hydrogenation (CTH) is a sustainable method for reducing unsaturated compounds, offering an alternative to high-pressure hydrogen gas.
- Asymmetric transfer hydrogenation (ATH) is crucial for enantioselective synthesis due to its simplicity and high stereocontrol.
Purpose of the Study:
- To compare base-assisted, base-free, and base-as-co-hydrogen-donor CTH methodologies.
- To analyze the role of bases in catalyst activation, hydride formation, reactivity, and selectivity.
- To identify factors differentiating base-assisted and base-free pathways and discuss future trends.
Main Methods:
- Review and comparison of diverse metal catalysts and substrates in CTH.
- Mechanistic analysis of base function (activator, co-donor) and base-free systems.
- Examination of ligand frameworks, metal-ligand cooperativity, and surface basicity in CTH.
Main Results:
- Bases like triethylamine, K2CO3, and NaOH activate catalysts and tune CTH reactivity and selectivity.
- Base-free CTH achieves high activity through tailored ligands, metal-ligand cooperativity, and engineered basicity.
- Formic acid systems exhibit dual base functions, and mixed bases show synergistic effects.
Conclusions:
- Understanding the role of bases is key to optimizing CTH efficiency and selectivity.
- Base-free CTH strategies offer additive-minimized, sustainable synthetic routes.
- Future CTH development focuses on greener hydrogen donors, advanced catalysts, and reduced additive use.
Keywords:
activityadditivebase-freecatalytic transfer hydrogenationhydrogen donorreduction reactionselectivityMore Related Videos
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