Theoretical studies on the structure and mechanism of the thermal N-nitropyrazole Rearrangement

초록

In this work, we studied the thermal rearrangements of N-nitropyrazoles and related heterocyclic compounds. These rearrangements occur in two-step mechanism. The first step involves migration of nitro group from nitrogen to carbon, which breaks the aromaticity of N-nitropyrazole. In the second step, a hydrogen atom transfers to the nitrogen atom, resulting in recovery of the aromaticity. In this mechanism, the first step is identified as the rate-determining step. All the molecules were fully optimized at the hybrid density functional B3LYP level with 6-31+G(d) and 6-311+G(d,p) using the Gaussian 03 program. These structures were verified as a minimum with no imaginary frequency and as a transition state with only one imaginary frequency by performing the frequency calculations.