N-oxidation of pyridine carboxylic acids using hydrogen peroxide catalyzed by a green heteropolyacid catalyst: Preyssler's anion, [NaP5W30O110]14−

The catalytic oxidation of pyridine carboxylic acids such as nicotinic acid, picolinic acid and quniolinic acid to the corresponding N-oxides has been studied using hydrogen peroxide as an oxidant and Preyssler's catalyst as pure acid, H14[NaP5W30O110] and mixed addenda, H14[NaP5W29MoO110]. The highly selective oxidations, gave good yields of the related N-oxides along with decarboxylation of the amines. In the production of pyridine N-oxides, the position of COOH group is found to play an important role in the product type and decarboxylation is only taken place at 2-position of nitrogen. The oxidation reactions were extended to other tertiary amines.

Graphical abstractPreyssler heteropolyacid with exclusive properties and along with retention of structure, in the presence of hydrogen peroxide catalyzes N-oxidation of the pyridine carboxylic acids to the related N-oxides with decarboxylation in 2-position with respect to nitrogen.Figure optionsDownload full-size imageDownload high-quality image (24 K)Download as PowerPoint slide