Reimer–Tiemann Reaction of Coumarins

Abstract

Improved yields of aldehydes from the Reimer–Tiemann reaction of coumarin and two of its derivatives, namely 7-methylcoumarin and 3,4-benzocoumarin, are obtained by carrying the reaction in a two-step procedure. Using crown ether as phase transfer catalyst, a further improvement in the yield of products is achieved. Additionally, coumarin and 7-methylcoumarin are shown to give dialdehydes under this condition. Dialdehydes are reported for the first time from the Reimer–Tiemann reaction.

Keywords:

• Bayer-Villiger oxidation
• crown ether
• coumarins
• dialdehyde
• Reimer–Tiemann reaction
• von Pechman reaction

ACKNOWLEDGMENTS

The authors acknowledge the financial assistance of the University Grants Commission in the form of minor research project grant. The authors also acknowledge the help of Dr. S. Nanda for recording the NMR spectra.

Notes

^{^}A: 12 hours reflux with 30% KOH solution and chloroform.

B: 8 hours reflux with 30% KOH solution followed by dilution and 4 hours reflux with chloroform.

C: 8 hours reflux with 30% KOH solution, then dilution and 1hour reflux with chloroform in presence of 5 mol% 18-crown-6.