Thermodynamic Network Cards of Hantzsch Ester, Benzothiazoline, and Dihydrophenanthridine Releasing Two Hydrogen Atoms or Ions on 20 Elementary Steps

In this work, thermodynamic driving forces on 20 possible elementary steps of Hantzsch ester (HEH2), benzothiazoline (BTH2), and dihydrophenanthridine (PDH2) releasing two hydrogen atoms or ions were measured or derived from the related thermodynamic data using Hess’ law in acetonitrile. Furthermore, thermodynamic network cards of HEH2, BTH2, and PDH2 releasing two hydrogen atoms or ions on 20 elementary steps were first established. Based on the thermodynamic network cards, hydride-donating, hydrogen-atom-donating, and electron-donating abilities of XH2 and XH–, and two hydrogen-atom­(ion)-donating abilities of XH2 are discussed in detail. Obviously, the thermodynamic network cards of HEH2, BTH2, and PDH2 not only offer rational data guidance for organic synthetic chemists to properly choose an appropriate reducer among the three reducing agents to hydrogenate various unsaturated compounds but also strongly promote elucidatation of the detailed hydrogenation mechanisms.