Novel electrochemical synthesis of oxadiazoles at graphite electrode

Electrochemical methods involve electrons transfer without the use of any oxidizing or reducing reagents and hence result in the formation of useful and/or novel organic compounds under mild conditions. In this paper, we report the preparation of 3-substituted-1,2,3-oxadiazole-5-one derivatives by the electrochemical reduction of 3-arylsydnones on graphite electrode is reported. The -N=N- moiety in these compounds undergo electrochemical reduction. Products of the electrolyzed species are isolated by bulk electrolysis at graphite electrode with a larger surface area. Characterizations of the reduced products are done by spectral and analytical data. The subject of organic electrochemical reactions is a fascinating and frontier area of research. Besides being of great academic interest, the exciting classes of chemical reactions belonging to this field are expected to be of great synthetic value. 3-substituted- 1,2,3-oxadiazol-5-one and their derivatives represents well known pharmacophoric scaffolds with a wide portfolio of interesting physiological activities. In general, the compounds belonging to this category possess potential anti-malarial, antiviral, chemotherapeutical, cortical muscarinic receptor and central muscle relaxant 1-5 , properties. Sydnones are a novel class of meso-ionic compounds containing 1,2,3-oxadiazole ring system. The study of sydnones still remains a field of interest because of their electronic structure and also varied types of biological activity associated with them 6 . Various methods are available for the chemical synthesis of 3-substituted-1,2,3-oxadiazole-5-one 7-9 . But hardly any report is available for the synthesis of 3-substituted-1,2,3-oxadiazole-5-one by electrochemical method. In view of these observations and in continuation of our research on developing electrochemical methods for the synthesis of organic molecules 10,11 , we report herein the electrochemical method for the synthesis of 1,2,3-oxadiazole derivative starting from appropriate sydnones.