A new method of selectively oxidizing aldehyde in anhydrous acetone system with KMnO4 was described. Using this method multi-ring alkyl benzoyloxy benzoic acids were prepared with the corresponding benzaldehydes as reactants. The oxidation activity of KMnO4 in the acetone system was researched by cyclic voltammetry. The mechanism of the reaction was also investigated by IR spectra. The structures of resulting products were confirmed by elemental analysis, IR, MS and 1H NMR spectra. The results showed that the anhydrous acetone system could lower the oxidation activity of KMnO4 remarkably, so in this system, KMnO4 possesses high selectivity to aldehyde as both aldehyde and alkyl groups all localized in a benzene ring. The selectivity was 100%. The optimum conditions of reaction confirmed by orthogonal test design in-clude reactant molar ratio of KMnO4∶reactant＝2∶1, the reaction time of 4 h and acidifying time of 1.5 h with the yield of 94%. Under the optimum condition, some compounds with similar structure were synthe-sized.

Key words: KMnO4, selective oxidation, aromatic acid, liquid crystal