DFT Study on Tautomerism of Dihydro‐2H‐1,5‐benzodiazepin‐2‐ones and Dihydro‐2H‐1,5‐benzodiazepine‐2‐thiones

Abstract

DFT calculations were performed to study the tautomeric rearrangements in the isolated, monoethanol-and diethanolsolvated, and dimeric forms of 4-methyl-1,3-dihydro-2H-1,5-benzodiazepin-2-one and 4-methyl-1,3-dihydro-2H-1,5-benzodiazepine-2-thione. Molecular geometries of the tautomers and transition state structures were optimized at the B3LYP/6-31G(d) and B3LYP/6-311++G(d,p) levels of theory. The long-range solvent effects on the geometrical and energy parameters of tautomerization were also analyzed by use of the PCM model. The calculated relative Gibbs free energies were used to estimate the equilibrium constants. It

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

“…Our results agree with those of Okovytyy et al [14] now including 3e : 3a (0.0) > 3b (14.7) > 3d (48.6) > 3e (64.0) > 3c (96.5). For the remaining compounds always is a (0.0) > b (18 kJ mol −1 in average), the other tautomers having considerably higher energies.…”

“…A comprehensive theoretical study of the tautomerism of 3 was carried out by Okovytyy et al in 2010, including monoethanol and diethanol solvates as well as dimeric forms [14] (they do not consider tautomer 3e ). In the gas phase their relative energies (in kJ mol −1 ) are: 3a (0.0) > 3b (14.6) > 3d (48.5) > 3c (93.4) and with an ethanol molecule they are: 3a (0.0) > 3b (0.6) > 3d (51.3) > 3c (70.0).…”

Mechanism of the Isotopic Exchange Reaction of the 5‐H Hydrogen of Uracil Derivatives in Water and Nonprotic Solvents

“…Although it was possible to converge this calculation, it did not yield a single-proton TS. These findings are in agreement with previous studies on the mechanism of the keto-enol tautomerism of nucleic acid bases, [19,[44][45][46] pyridine derivatives, [38][39][40][41] and other compounds [43,51] in aqueous media. It was found that the tautomerization reactions proceed preferentially by a multiple proton-transfer mechanism with the assistance of two to three water molecules.…”

DFT study on the tautomerism of organic linker 1H-imidazole-4,5-tetrazole (HIT)

“…For instance, the migration of the hydrogen atom to the nitrogen atoms in both the imidazole and the tetrazole rings can lead to the tautomeric forms. This is well rationalized with the earlier study on the prototropic tautomerism [31][32][33] through the migration of the hydrogen atom in both the imidazole [34][35][36] and the tetrazole rings [37][38][39].…”