Figure 4. Geometry of key intermediate and transition states showing bond distances (Å) of non-covalent interactions (blue) (mPW1PW91/6-31 + G(d,p)).

Mayer bond order for pTS-I are in parenthesis and blue. Reported energies are relative to starting materials: free energy in black non-italic bold and enthalpy in black italic bold. Dotted lines show hydrogen bonding (black) and C-C bond formation (orange). Non-interacting hydrogen atoms have been omitted for visual clarity. Atoms are color coded for each element: carbon (grey); hydrogen (white); oxygen (red); nitrogen (blue); fluorine (green); sulfur (yellow). Insert showing the Newman projection of the transition states from the perspective of the newly formed C-C bonds.