Fig. 5: Energy profiles and geometries of key transition states for the transamination of α-keto phosphonate.

a Energy profile of the condensation step. b Energy profile of the proton transfer step and geometries of key transition states. Relative Gibbs free energies are given in kcal/mol. Hydrogen bonds are shown as green dashed lines in the geometries of key transition states. Distances are reported in angstroms (Å). For clarity, the iodide and chloride counterions of catalyst 1a were excluded from the DFT calculations and are not shown. TFE trifluoroethanol.