Manganese(II) Porphyrin and Cumyl Hydroperoxide: An Efficient Catalyst for Aryl‐Pentazole C−N Bond Cleavage

The selective cleavage of C-N bonds in N-containing compounds holds significant research value in organic synthesis, particularly for the synthesis of promising polynitrogen species. For instance, the discovery of the cyclo-pentazolate (cyclo-N₅ ^-) anion in 2017 as a result of cleavage of the C-N bond has sparked interest within the field of high energy density materials. However, previous methods using ferrous glycinate and m-chloroperoxybenzoic acid generated the cyclo-N₅ ^- anion in a low yield of 19.5 % after 24 hours, and the mechanism remained unclear. In this study, we developed an efficient catalytic system comprising Mn (II) tetraphenylporphyrin and cumyl hydroperoxide. This system enables the cyclo-N₅ ^- anion to be produced from 3,5-dimethyl-4-hydroxyphenylpentazole in 35.4 % yield in 4 hours. Characterization of Mn(IV)-oxo porphyrins, ^⋅CH₃, and ^⋅C₈H₈ON₅ radicals provides evidence for the mechanism whereby the cyclo-N₅ ^- anion forms. Our study underscores the competitive potential of radical-initiated selective C-N bonds cleavage in N-arylazoles and opens avenues for further exploration in this field.