12-Phosphotungstic acid supported on silica gel, zirconium sulfate, and a combination of silica gel and zirconium sulfate (50% w/w) were employed as solid acid catalysts for regioselective acylation of 2-methoxynaphtalene with acetic anhydride. 1-(6-Methoxynaphthalen-2-yl)ethanone (2,6-AMN), a commercially important intermediate for production of Naproxen, was obtained with excellent selectivity (>98%) at 67-68% conversion using 12-phosphotungstic acid supported on silica gel 20% (w/w) in refluxing tetrachloroethane. The unreacted starting material can be easily separated from the product by a simple crystallization from nonane.
Bibliographical noteFunding Information:
We thank CSIR New Delhi for financial support under XII 5 year plan CSC0108-ORIGIN, and Prof. Dr V Vishwanathan, Sreyas Institute of Engineering and Technology, Hyderabad for helpful discussions.
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- Phosphotungstic acid
- Silica gel
- Zirconium sulfate