Dataset

In this project, the stereoselective reaction of 1,4-dicarbonyls with diarylprolinol silyl ether catalysts was studied with force field and density functional theory calculations. A robust procedure has been developed for computational investigations of large and flexible chemical systems based on the conformation labelling system, ONIOM calculations and Python scripting. The change in enantiomeric excess due to variations in the catalyst can be explained based on conformational changes and structural deformations. In the enantioselectivity-determining radical addition step, the iminium in the most stable SR transition state (TS) takes up the conformation of the most stable ground state iminium (EE). The conjugated iminium in the SS TS adopts an EZ conformation to avoid potential structural deformations due to radical attacks from the more sterically hindered position. For systems with simpler catalysts, the iminium is EE for both, as the steric hindrance imposed by the substituent is not sufficient to cause this large structural deformation, and so the reaction shows poor enantioselectivity. The key DFT structures are included in the ‘SI_key_structure’ folder as Gaussian calculation output files.

Files can be opened annd viewed using any text editor Conformational searching calculations were conducted in Macro-Model (v11.7) with Merck Molecular Force Field (MMFF). DFT optimisations were performed with Gaussian 16 (Revision B.01). All the structures are the most stable conformer in their corresponding group. Both the opt+freq calculation and its associated single point energy output (i.e. _solv_wb.out files) are included for each structure. The corresponding level of theory is ωB97X-D/6-311++G(d,p)/SMD/CH3CN//B3LYP/6-31G(d). The filename should be self-explanatory. For example, ‘B_Me_RPh_R_801_TS.out’ implies a catalyst B SR TS (R1 = Me; R2 = Ph) and ‘C_Me_EE_2.out’ implies a catalyst C iminium (R1 = Me) structure.