Electrophilicity, mechanism and structure–reactivity relationships of cyclic secondary amines addition to 2-methoxy-3,5-dinitropyridine

•SET mechanism has been suggested to describe the nucleophilic aromatic substitution reactions of 2‑methoxy-3,5-dinitropyridine by secondary cyclic amines in acetonitrile solution.•E values of six anisoles have been predicted according to the E vs ω correlation (Eq.I) demonstrated in this work and found to agree with those reported in the literature.E = −93.41 + 23.73 ω (R2 = 0.9997) (I).•The expansion of the applicability of Mayr's equation (II) to these types of processes further demonstrates the generality of this relationship. log k (20 °C) = sN (E + N) (II). The second-order rate constants (k) for the nucleophilic aromatic substitution reactions of 2‑methoxy-3,5-dinitropyridine 1 with secondary cyclic amines 2a-c in acetonitrile solution at 20 °C are reported. The logarithms of these rate constants are particularly significant as possible measures of the electrophilicity parameters E for 2‑methoxy-3,5-dinitropyridine 1 according to the linear free energy relationship log k (20 °C) = sN(N + E). Additional kinetic data for reactions of 2-methoxy-3,5-dinitropyridine 1 with a series of nitroalkyl anions in DMSO solution are also measured and found to agree with those calculated by Mayr's approach from the known two solvent-dependent parameters N and sN of nitroalkyl anions and the electrophilicity parameter E measured in this work. A Single Electron Transfer (SET) mechanism is proposed for the SNAr reactions, on the basis of the linear Brönsted plot with the βnuc value of 0.94. The validity of this mechanism is confirmed by the agreement between the rate constants, k, and the oxidation potentials E° of these series of secondary cyclic amines. Also, reactivity descriptors such as the electronic chemical potential (μ), and the chemical hardness (η) for a series of pyridine derivatives were calculated by Density Functional Theory (DFT), and it is shown that the global electrophilicity index (ω = μ2/2η) is significantly correlated with the electrophilicity parameters E. The E parameters of various anisoles (see Figure) were derived from the correlation between experimentally measured electrophilicities (E) and global electrophilicity index (ω) calculated at B3LYP/6-311g(d,p) level for a series of pyridines. [Display omitted]