Fig. 5: Calculated transition states of Mannich reaction.

The structures of TSs to form 8a by Mannich reaction catalysed by ent-3b and 4f at the M06-2X/6-31(d) // M06-2X/6-31 + +G(d,p) level and energy are given in kcal/mol relative energy of M-ent-3b-RR-TS1 and M-4f-RS-TS1. Dr and ee values shown in the parentheses are the predicted data by the computational study.