The Aldol Reaction under High-Intensity Ultrasound: A Novel Approach to an Old Reaction
Giancarlo Cravotto*, Alberto Demetri, Gian Mario Nano, Giovanni Palmisano, Andrea Penoni, Silvia Tagliapietra
*Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Via
Giuria 9, 10125 Torino, Italy, Email: giancarlo.cravotto
unito.it
G. Cravotto, A. Demetri, G. M. Nano, G. Palmisano, A. Penoni, S. Tagliapietra, Eur. J. Org. Chem., 2003, 4438-4444.
DOI: 10.1002/ejoc.200300369
Abstract
High-intensity ultrasound was employed to reinvestigate the aldol reaction in water. A number of aldols that would eliminate or form side products under conventional conditions were isolated in good yields within minutes. The results are highly reproducible because the sonochemical parameters were rigorously controlled.
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Details
The document discusses a novel approach to the aldol reaction (AR) using high-intensity ultrasound (HIU) in water. The AR, a fundamental organic reaction forming C=C bonds and stereocenters, often suffers from low yields due to side reactions. Traditional methods include acid/base catalysis and the Mukaiyama AR. The study found that HIU significantly enhances reaction rates and yields, isolating aldols that typically undergo elimination. Acetophenone and non-enolizable aldehydes reacted efficiently under HIU, producing aldols exclusively within 15-30 minutes, compared to hours under conventional methods. The use of water as a solvent offers environmental benefits and unique reactivities. The addition of surfactants like Aliquat® 336 further improved yields. The method also facilitated the synthesis of polyols and bis(benzylidene) adducts, important for producing lubricants, coatings, and resins. The results were reproducible due to controlled sonochemical parameters. This approach contributes to green chemistry by reducing reaction times, improving yields, and minimizing the need for catalysts. The study highlights the potential of HIU in developing efficient and sustainable synthetic methods.
Key Words
aldol reactions, addition, condensation, sonochemistry
ID: J24-Y2003-870
