Studying Double Group Transfer Reactions by Means of Computational Methods

Abstract

In this article, recent computational studies focused on double group transfer reactions and related processes are summarized. The reported results clearly indicate that these transformations can be considered as a subclass of pericyclic reactions occurring concertedly, with high activation barriers and synchronicity values, and through highly symmetric transition states. Interestingly, the aromatic nature of the latter saddle points has been also studied and discussed showing that they can be viewed as the in-plane analogues of sixmembered hetero-aromatic rings. Finally, the application of the so-called "Strain Model" on these important processes has demonstrated that the strain (the energy required to deform the reactants to the geometry they present in the corresponding transition state) is the major factor controlling the high barrier heights in spite of the stabilizing contribution of the aromaticity.

exo/endo Selectivity Control in Diels–Alder Reactions of Geminal Bis(silyl) Dienes: Theoretical and Experimental Studies

“…In comparison to Δ E int , the distortion energy term (Δ E strain ) became the major factor controlling the activation barrier of the overall process as well as the ΔΔ G value of the two competing pathways. A similar behavior was also observed in other pericyclic reactions. − We then decomposed further the total Δ E strain into two energy contributors: that is, the deformation energies of the catalyst-associated dienophile fragment 2a-LA (Δ E strain(2a‑LA) ) and the diene 1a fragment Δ E strain(1a) (shown in Figure b). In comparison to the favorable exo pathway, a stronger destabilization of the 2a-LA fragment in the Δ E strain curve was observed along the endo pathway, especially in the proximity of the corresponding TS region.…”

Reaction mechanisms: pericyclic reactions

“…Fernandez and Cossio provided a review on theoretical studies on double group transfer reactions (e.g., Scheme 33), which are generally synchronous concerted processes with aromatic transition state structures. 44 Das and co-workers described B3LYP calculations aimed at assessing the effects of remote substituents on the facial selectivity of carbonyl ene reactions (e.g., Scheme 34). 45 On the basis of their results, the authors suggested that both electrostatic and hyperconjugation effects can affect selectivity.…”