Figure 3. Geometries of the stationary points in the formation
of anion intermediate 2a’ from isatin (2a ).
Elementary reaction 2.
Nucleophilic addition occurs between intermediates 1a’ and2a’ . Electron-rich N(28) of 2a’ attacks C(6) of the
dipole intermediate, 1a’ , leading to the formation of
intermediate med1 through transition state TS2. The geometry of each
stationary point is shown in Figure 4.