Fig 4. Spin densities and AIM analysis.

For the sake of comparison, the same isosurface of value 0.003 |e|/ų representing the difference between the alpha and beta electron densities was depicted in violet or green, for the 4-endo and 5-endo forms respectively. For the products and the intermediate species on the product side (IC_P), the presence of bond critical points (bcp) was evidenced by means of AIM. The bcp connecting the carboxyl group to the pyrrolidine ring is depicted in violet or green, whereas the remainder bcps are shown in gray. The nuclear critical points (located at the position of the nuclei), the basin paths, and the gradient field are depicted in solid or dashed black lines. The bond paths, defined by the chosen 2D projection (plane), are shown in red.