Oxidation of cyclopentene catalyzed by phosphotungstic quaternary ammonium salt catalysts

A series of phosphotungstic quaternary ammonium salts, Q3 (PW12O40) and Q3(PW4O16) [Q = (C5H5)N+(C16H33), (C16H33)N+(CH3)3, (C4H9)4N+, and (CH3)4N+], were used as the catalysts in oxidation of cyclopentene. The catalysts [(C5H5)N(C16H33)]3(PW4O16) and [(C16H33)N(CH3)3]3(PW4O16) showed high catalytic activity in the selective oxidation of cyclopentene while using H2O2 (50%) as an oxidant and 2-propanol as a solvent. The oxidation products mainly consisted of glutaraldehyde, cis-1,2-cyclopentanediol and trans-1,2-cyclopentanediol. The above-mentioned two catalysts were dissolved completely in the reaction medium during the catalysis process and precipitated themselves from the reaction system after reaction, showing the characteristics of reaction-controlled phase-transfer catalysis. The types of quaternary ammonium cations and the phosphotungstic anions in phosphotungstic quaternary ammonium salts affected catalytic activity.