1.2.4- Oxadiazole catalytic reduction

Catalytic reduction of 1,2,4-oxadiazoles also breaks the N—O bond e.g. (264) gives (265). Benzofuroxan can be reduced under various conditions to benzofurazan (266), the dioxime (267) or o-phenylenediamine (268) (69AHC(10)l). Reduction by copper and hydrochloric acid produced o-nitroanilines (Scheme 30) (69AHC(lO)l). 

Catalytic reduction161,162 with various catalysts (Pt02, Pd/C, or Raney Ni) on other oxadiazoles all broke the N—0 bond [Eqs. (47-49)]. The product in one case (52) was acetamidine benzoate, which suggested the reduction pathway shown in Eq. (47). 

Repeated cycling through the RUB reduction wave resulted in a decrease in size of the catalytic current. This occurred even when the solution was stirred between cycles. This behavior implies that a blocking or filming of the electrode occurred during the reduction process. Repeated cycling over the oxidation wave removed the film and reactivated the electrode. The electrochemical reduction of 9,10-diphenylanthracene (DPA), 1,3,6,8-tetraphenylpyrene (TPP), anthracene (ANT), fluoranthene FLU) and 2,5-diphenyl-l,3,4-oxadiazole (PPD) in the presence of S Os - all showed similar cathodic waves. 

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