To disclose the origin of the deficiencies in correctly describing the hydride transfer reaction by the DFTB3 Hamiltonian, we optimized the transition state at the M06-2X/def2-TZVP level of theory in vacuum. Then, we calculated the activation barrier using different DFT functionals and post-HF methods to validate an accurate and computationally efficient electronic structure method (see Table in the Supporting information). The benchmark evidences that the M06-2X functional in combination with the def2-TZVP basis set describe the potential energy difference between reactants and transition state accurately as well as the potential energy difference to the enolate, the product of the hydride transfer reaction.