Generally, the mole ratio of N-oxide of 2-pyridine thiol to aluminum isopropylate is 2:1 and the reaction is usually carried out in an anhydrous solvent such as an alcohol, and more particularly methyl, ethyl, isopropyl andtertio-butyl alcohol, an aromatic hydrocarbon such as benzene and toluene, or a chlorinated hydrocarbon such as chloroform and dichlorethane.