This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Amide bonds are chemical linkages essential to biology, medicine and materials chemistry. Peptide bonds, a class of amide bonds, link amino acids to form proteins.
Amide bonds are also important in medicines and polymers. Efficient synthesis of amide bonds remains a major focus in green chemistry. Most practical approaches to amide synthesis require coupling reagents to activate carboxylic acids before they can react with amines to form amides.
However, many commonly used reagents can be corrosive or toxic, release hazardous byproducts and generate substantial waste, creating challenges for large-scale synthesis. An ideal coupling reagent would be cost-effective and stable, and produce only benign byproducts that are easy to eliminate. A research team led by Sunwoo Lee, a professor in the Department of Chemistry at Chonnam National University in South Korea, used dichloromethane as a coupling reagent for direct amide bond synthesis from carboxylic acids and amines.
"Dichloromethane is a commonly used solvent in many chemical processes," Lee said. "In this study, we present the successful application of this common solvent to facilitate efficient and scalable amide bond formation." The study is published in the Journal of the American Chemical Society. The researchers found that under basic conditions, carboxylates can attack dichloromethane through an SN2 reaction to generate reactive chloromethyl ester intermediates.
These intermediates can then undergo acyl substitution with amines to produce amides. Using benzoic acid and benzylamine as model substrates, the researchers optimized the reaction conditions. Initial results showed that sodium carbonate as the base, dichloromethane as the coupling reagent and dimethyl sulfoxide as the solvent enabled the desired amide formation in good yield.
Optimal efficiency and reproducibility required a temperature of 80 °C (176 °F), a 12-hour reaction time and an excess of amine. Further experiments showed that the method worked across a broad range of carboxylic acids and amines. The researchers synthesized two pharmaceutical amides using this approach: the antiarrhythmic agent procainamide with a 92% yield and the antidepressant moclobemide with a 76% yield.
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