Phosphotungstic acid salt of triphenyl(3-sulfopropyl)phosphonium: An efficient and reusable solid catalyst for esterification

The organic Keggin-structured heteropolyacid salt was synthesized by combining phosphotungstic anion with sulfonated quaternary alkylphosphonium cation. It was characterized, and catalytically evaluated in esterification. The salt has an ionic liquid-like composition but possesses a high melting-point near 200 °C. It exhibits high yields and selectivity for target esters in various esterification reactions. Moreover, it can be conveniently recovered and steadily reused.