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An Efficient and Practical Procedure for the Synthesis of 4-Substituted Coumarins

Surya K. De*, Richard A. Gibbs

*Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy, Purdue Cancer Center, Purdue University, West Lafayette, IN 47907, USA, Email: skd125pharmacy.purdue.edu

S. K. De, R. A. Gibbs, Synthesis, 2005, 1231-1233.

DOI: 10.1055/s-2005-865282


Abstract

BiCl3 is used as an efficient catalyst in the Pechmann condensation reaction of phenols with β-keto esters leading to the formation of coumarin derivatives in excellent yields under solvent-free conditions.

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Details

The document discusses an efficient and practical method for synthesizing 4-substituted coumarins using bismuth(III) chloride (BiCl3) as a catalyst in the Pechmann condensation reaction of phenols with β-keto esters. This method is notable for its solvent-free conditions, high yields, and reduced reaction times. Traditional methods for synthesizing coumarins often involve the use of excess hazardous acids and high temperatures, leading to environmental concerns and unwanted side products. In contrast, BiCl3 is relatively non-toxic, inexpensive, and environmentally benign, making it a suitable alternative. The study demonstrates that various phenols, especially those with electron-donating groups, react efficiently with ethyl acetoacetate to produce coumarin derivatives. The method tolerates different functional groups and operates under milder conditions compared to previous methods. The procedure involves heating a mixture of resorcinol, ethyl acetoacetate, and BiCl3 at 75°C for one hour, followed by cooling and recrystallization to obtain the pure product. This new method offers advantages in terms of operational simplicity, economic viability, and environmental safety, making it a valuable addition to current synthetic methodologies for coumarins.


Key Words

phenols, β-keto ester, Pechmann reaction, bismuth(III) chloride, coumarin


ID: J66-Y2005-760