First generation of pentazole (HN5, pentazolic acid), the final azole, and a zinc pentazolate salt in solution: A new N-dearylation of 1-(p-methoxyphenyl) pyrazoles, a 2-(p-methoxyphenyl) tetrazole and application of the methodology to 1-(p-methoxyphenyl) pentazole

Abstract

Ceric ammonium nitrate (CAN) in methanol–water gave a new N-dearylation of a series of substituted 1-(p-methoxyphenyl) pyrazoles and a 2-(p-methoxyphenyl)tetrazole producing p-benzoquinone and the parent azole in a mole for mole ratio. Application of this reaction to 1-(p-methoxyphenyl) pentazole at −40 °C produced p-benzoquinone. ¹⁵N NMR spectra suggest that pentazole, HN₅, was also produced and held in solution as N₅⁻ with Zn²⁺ ion. The ¹⁵N signal from N₅⁻ was −10.0 ± 2.0 ppm in agreement with calculated values.