Highly Efficient and Scalable Process for Demethylation of 6-(2,4-Dimethoxybenzoyl)chromen-2-one and Other Aryl Methyl Ethers

Abstract

Demethylation of 6-(2,4-dimethoxybenzoyl)chromen-2-one and some other aryl methyl ethers was achieved with pyridinium bromide as demethylating agent and sulfolane as solvent. Compared with other demethylation methods, this combination offers advantages of clean conversion, excellent yields, easy operation and workup, and manageable reaction temperatures. This process could be particularly useful for large-scale production because it avoids use of corrosive or moisture-sensitive reagents.

Keywords:

• Aryl methyl ethers
• demethylation
• 6-(2,4-dimethoxybenzoyl)chromen-2-one
• pyridinium bromide
• sulfolane

ACKNOWLEDGMENT

We thank Toyama Chemical Co., Ltd., Toyama, Japan, for providing a sample of 6-(2,4-dimethoxybenzoyl)chromen-2-one (1) and initial laboratory procedures.

Notes

^a Product area % based on in-process control HPLC analysis.

^a Product area % based on in-process control HPLC analysis.

^b Reaction was clean, but product isolation was not attempted.