Related Experiment Video
Updated: May 12, 2025

Author Spotlight: Standardizing the Development of Amine-Based Silica Composites as CO2 Adsorbents for Direct Air Capture
Published on: September 29, 2023
Calcium Impregnated Silica Gel in the Domino Reaction Involving Irreversible Aldol Addition, Dehydration, and Michael
Jih Ru Hwu1, Khagendra Prasad Bohara1, Animesh Roy1
1Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan.
Abstract:
An innovative method was developed for the performance of aldol additions in an irreversible fashion by the use of calcium metal impregnated silica gel (Ca@SiO2) as a remarkable reducing reagent. In this approach, Ca@SiO2 drove the reaction forward, prevented reversibility, and ensured the formation of the desired products. Thus, in the presence of Ca@SiO2 (3.0 equiv), aldehydes (1.0 equiv) condensed with ketones (1.0 equiv) in 2-MeTHF to yield α,β-unsaturated enones in 71-90% yields at 25 °C. Additionally, a domino reaction involving successive aldol addition, dehydration, and Michael addition was developed for the preparation of 1,5-diketones. Accordingly, when aldehydes (1.0 equiv) were allowed to react with ketones (2.2 equiv) and Ca@SiO2(4.0 equiv), 1,5-diketones were produced in 67-88% yields. These reactions involved radical processes, where Ca@SiO2 abstracted two α hydrogen atoms from ketones and the oxygen atom from aldehydes to form CaH2@SiO2 and CaO@SiO2, respectively. These species were confirmed by powder X-ray diffraction analysis. The resultant impregnated silica gel species were solid and insoluble in the reaction mixtures, which made the addition reactions irreversible. This method represents a significant advancement in aldol condensation reactions and offers the advantages of both atom economy and atom efficiency.
More Related Videos
Related Concept Videos
Base-Catalyzed Aldol Addition Reaction
C–C Bond Formation: Aldol Condensation Overview
Acid-Catalyzed Aldol Addition Reaction
Aldol Condensation vs Claisen Condensation
Dehydration of Aldols to Enals: Base-Catalyzed Aldol Condensation
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation

