In this regard, a team of scientists led by Michikazu Hara (Tokyo Institute of Technology) has reported the highly chemoselective acetalization of biomass-derived 5-hydroxymethylfurfural (HMF) with alcohols using a monoclinic CePO 4 . CePO 4 , corresponding to rare earth (RE) orthophosphates, are expected to be suitable bifunctional acid-base catalysts, where the synergistic promotion of electrophilicity and nucleophilicity in reactive partners could be achieved.
Mechanistic studies indicated that CePO 4 most probably serves as a bifunctional catalyst via the interaction of uniform Lewis acid and weak base sites with HMF and alcohol molecules, respectively, leading to high catalytic performance. Activation of HMF and methanol by CePO 4 facilitates the nucleophilic attack of OH in methanol on the carbon atom of C=O, affording the hemiacetal derivative. Next, the reaction between the derivative and methanol by the assistance of CePO 4 leads to the acetal. The effectiveness of the bifunctional properties of CePO 4 was evidenced by the wide applicability to various acetals including industrially important solketal.
This study discusses a promising strategy employing highly efficient heterogeneous catalysts via the non-dissociative activation of electrophiles and nucleophiles under extremely mild conditions.
