Sulfonyl hydrazides are viewed as alternatives to sulfinic acids and their salts or sulfonyl halides, which are broadly used in organic synthesis or work as active pharmaceutical substances. Generally, sulfonyl hydrazides are considered good building blocks and show powerful value in a diverse range of reactions to construct C-S bonds or C-C bonds, and even C-N bonds as sulfur, carbon, or nitrogen sources, respectively. As a profound synthetic tool, the electrosynthesis method was recently used to achieve efficient and green applications of sulfonyl hydrazides. Interestingly, many unique and novel electrochemical syntheses using sulfonyl hydrazides as radical precursors have been developed, including cascade reactions, functionalization of heterocycles, as well as a continuous flow method combining with electrochemical synthesis since 2017. Accordingly, it is necessary to specifically summarize the recent developments of electrosynthesis with only sulfonyl hydrazides as radical precursors to more deeply understand and better design novel electrochemical synthesis reactions. Herein, electrosynthesis research using sulfonyl hydrazides as radical precursors since 2017 is reviewed in detail based on the chemical structures of products and reaction mechanisms.

The purpose of this study is to investigate thermodynamic and kinetic properties on the hydrogen-atom-donating ability of 4-substituted Hantzsch ester radical cations (XRH^•+), which are excellent NADH coenzyme models. Gibbs free energy changes and activation free energies of 17 XRH^•+ releasing H^• [denoted as ΔG_HD^o(XRH^•+) and ΔG_HD^≠(XRH^•+)] were calculated using density functional theory (DFT) and compared with that of Hantzsch ester (HEH₂) and NADH. ΔG_HD^o(XRH^•+) range from 19.35 to 31.25 kcal/mol, significantly lower than that of common antioxidants (such as ascorbic acid, BHT, the NADH coenzyme, and so forth). ΔG_HD^≠(XRH^•+) range from 29.81 to 39.00 kcal/mol, indicating that XRH^•+ spontaneously releasing H^• are extremely slow unless catalysts or active intermediate radicals exist. According to the computed data, it can be inferred that the Gibbs free energies and activation free energies of the core 1,4-dihydropyridine radical cation structure (DPH^•+) releasing H^• [ΔG_HD^o(DPH^•+) and ΔG_HD^≠(DPH^•+)] should be 19–32 kcal/mol and 29–39 kcal/mol in acetonitrile, respectively. The correlations between the thermodynamic driving force [ΔG_HD^o(XRH^•+)] and the activation free energy [ΔG_HD^≠(XRH^•+)] are also explored. Gibbs free energy is the important and decisive parameter, and ΔG_HD^≠(XRH^•+) increases in company with the increase of ΔG_HD^o(XRH^•+), but no simple linear correlations are found. Even though all XRH^•+ are judged as excellent antioxidants from the thermodynamic view, the computed data indicate that whether XRH^•+ is an excellent antioxidant in reaction is decided by the R substituents in 4-position. XRH^•+ with nonaromatic substituents tend to release R^• instead of H^• to quench radicals. XRH^•+ with aromatic substituents tend to release H^• and be used as antioxidants, but not all aromatic substituted Hantzsch esters are excellent antioxidants.

32 F420 coenzyme models with alkylation of the three different N atoms (N₁, N₃ and N₁₀) in the core structure (XFH⁻) were designed and synthesized and the thermodynamic driving forces (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the 32 XFH⁻ releasing hydride ions, hydrogen atoms and electrons, the thermodynamic driving forces of the 32 XFH˙ releasing protons and hydrogen atoms and the thermodynamic driving forces of XF⁻˙ releasing electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The effects of the methyl group at N₁, N₃ and N₁₀ and a negative charge on N₁ and N₁₀ atoms on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were examined; the results show that seating arrangements of the methyl group and the negative charge have remarkably different effects on the thermodynamic properties of the F420 coenzyme models and their related reaction intermediates. The effects of the substituents at C₇ and C₈ on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were also examined; the results show that the substituents at C₇ and C₈ have good Hammett linear free energy relationships with the six thermodynamic parameters. Meanwhile, a reasonable determination of possible reactions between members of the F420 family and NADH family in vivo was given according to a thermodynamic analysis platform constructed using the elementary step thermodynamic parameter of F420 coenzyme model 2FH⁻ and NADH model MNAH releasing hydride ions in acetonitrile. The information disclosed in this work can not only fill a gap in the chemical thermodynamics of F420 coenzyme models as a class of very important organic sources of electrons, hydride ions, hydrogen atoms and protons, but also strongly promote the fast development of the chemistry and applications of F420 coenzyme.

The H-donating activity of phenol and the H-abstraction activity of phenol radicals have been extensively studied. In this article, the second-order rate constants of 25 hydrogen atom transfer (HAT) reactions between phenols and PINO and DPPH radicals in acetonitrile at 298 K were studied. Thermo-kinetic parameters ΔG^≠o(XH) were obtained using a kinetic equation [ΔG^≠ _XH/Y = ΔG^≠o(XH) + ΔG^≠o(Y)]. Bond dissociation free energies ΔG^o(XH) were calculated by the iBonD HM method, whose details are available at https://pka.luoszgroup.com/bde_prediction. Intrinsic resistance energies ΔG^≠ _XH/X and ΔG^≠o(X) were determined as ΔG^≠o(XH) and ΔG^o(XH) were available. ΔG^o(XH), ΔG^≠ _XH/X, ΔG^≠o(XH) and ΔG^≠o(X) were used to assess the H-donating abilities of the studied phenols and the H-abstraction abilities of phenol radicals in thermodynamics, kinetics and actual HAT reactions. The effect of structures on these four parameters was discussed. The reliabilities of ΔG^≠o(XH) and ΔG^≠o(X) were examined. The difference between the method of determining ΔG^≠ _XH/X mentioned in this study and the dynamic nuclear magnetic method mentioned in the literature was studied. Via this study, not only ΔG^o(XH), ΔG^≠ _XH/X, ΔG^≠o(XH) and ΔG^≠o(X) of phenols could be quantitatively evaluated, but also the structure–activity relationship of phenols is clearly demonstrated. Moreover, it lays the foundation for designing and synthesizing more antioxidants and radicals.