A Systematic theoretical study of thermal N-nitropyrazole

초록

Thermal N-nitropyrazole rearrangement is a very useful method to introduce the nitro group on 5-position of the pyrazole. 40-years ago, Louw and his research group have reported the evidence for the sigmatropic nitro migration using the experimental methods (see Figure 1).[1] Nevertheless, there have been still a few theoretical studies for this mechanism.[2, 3] Generally, these rearrangements occur in two-step mechanism. The first step involves migration of the nitro group from nitrogen to carbon, which breaks the aromaticity of N-nitropyrazole. Then, a hydrogen atom transfers to the nitrogen atom, resulting in recovery of the aromaticity. The first step was identified as the ratedetermining step. And these nitro group migrations were also found in some heterocyclic compounds.