Application of polyethylene glycol-based aqueous biphasic reactive extraction to the catalytic oxidation of cyclic olefins

Glutaric acid and 1,2,3,4-butanetetracarboxylic acid (BTCA) have been synthesized by sodium tungstate catalyzed oxidation of the cyclic olefins: cyclopentene and 1,2,3,6-tetrahydrophthalic anhydride (THPA), using hydrogen peroxide in a polyethylene glycol (PEG)-2000/NaHSO4 aqueous biphasic system (PEG-ABS). The production of glutaric acid and BTCA was found to increase from the monophasic to the biphasic regimes, and was found to be greatest at short tie-line lengths (TLLs), close to the system’s critical point, yielding glutaric acid and BTCA in 73.1 and 82.5% yield, respectively. The results imply that mutual mixing or contact of the components is important, because the product dicarboxylic acids were found to increase from the monophasic side to the critical point and decrease from the critical point to more divergent regimes. The two reactions were compared with adipic acid synthesis from cyclohexene in terms of the cyclic olefin structure, and the partitioning of the dicarboxylic acid product in the ABS.