A Convenient Method for One Step Oxidative Decarboxylation by KMnO 4 in Non Aqueous Media

In this report a novel application of potassium permanganate, a stable, non-toxic, widely available and inexpensive chemical, as an oxidant in organic chemistry is described. Potassium permanganate is normally employed as a neutral or alkaline aqueous solution. If an organic compound is not soluble in water, it may be investigated as a suspension in the aqueous permanganate solution, or a co-solvent such as t-butyl alcohol or acetic acid may be employed. 15 According to this research, the reaction of potassium permanganate with phenylacetic acid, (4-methoxyphenyl) acetic acid, (4-hydroxyphenyl) acetic acid, and benzilic acid in an organic solvent (CH 2 Cl 2 or CHCl 3 ) resulted in preparation of benzaldehyde, (4-methoxy) benzaldehyde, (4-hydroxy) benzaldehyde, and benzophenone, respectively. Surprisingly, benzylmalonic acid reacted with potassium permanganate under the same conditions and benzaldehyde formed. It is noteworthy that, in all of the mentioned reactions no vigorous conditions (heat or reflux) and no catalyst) acid or alkali media) were used. The reactions were simply performed in high yields only with stirring at room temperature. The MnO 2 and CO 2 that were obtained as side-products in the reactions were tested by conventional methods. The optimized conditions for oxidative decarboxylation reactions were listed in Table 1. Under the reaction conditions no further oxidation of the obtained product (aldehyde or ketone) to corresponding acids was observed. Presence of the activated benzylic hydrogen seems to be an important factor in oxidative decarboxylation reaction.