Understanding the molecular mechanism of thio-Claisen rearrangement of allyl phenyl sulfide and allyl vinyl sulfide using bonding evolution theory coupled with NCI analysis

Are There Only Fold Catastrophes in the Diels–Alder Reaction Between Ethylene and 1,3-Butadiene?

“…Moreover, a description of changes of the topologically defined molecular structures as a response to the variation of control parameters can be addressed via the theory of elementary catastrophes. , It has been mainly exploited within both the QTAIM and ELF ,, frameworks. Within the so-called bonding evolution theory (BET) framework, the transformation of the topology of the ELF along a chosen reaction path (e.g., the intrinsic reaction coordinate (IRC) , ) are characterized in terms of Thom’s elementary catastrophes. ,,, The BET has a demonstrated capability for studying the evolution of the rearrangement of electron pairing (as measured by the ELF) along the reactive path, and hence, chemically significant events, including bond making/breaking processes, become naturally associated with specific structural stability domains (SSDs) separated by catastrophe bifurcations. ,,, BET has provided meaningful insights on an ever-increasing number of reactive processes related to problems in almost all fields of chemistry, , including, for instance, key questions on bonding and reactivity related to the activation of C–H bonds, proton/hydrogen transfer reactions, [4 + 2] cycloadditions, , [3 + 2] cycloadditions, , [1,3] dipolar cycloadditions, ,, the process of fixation of CO 2 by metal complexes, decarbonylation of unsaturated cyclic ketones, the nature of phase transitions for the group IV elements, the formation of hemiaminals, , Cope , and Claisen − rearrangements, the thermal decomposition of α-ketoesters, hydrometalation of acetylene, oxidative additions of ammonia to pincer complexes, the Curtis rearrangement, the catalytic Noyori hydrogenation, and the Wittig reaction . We stress that any chemical reaction can, in principle, be in such a way represented in terms of a precise sequence of catastrophic bifurcations associated with electron pairing topologies that enable a straightforward rationalization or interpretation of the evolution of the key chemical concept of bonding patterns. ,,, …”

Deciphering the Curly Arrow Representation and Electron Flow for the 1,3-Dipolar Rearrangement between Acetonitrile Oxide and (1S,2R,4S)-2-Cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl Acetate Derivatives

“…31 BET allows us to perceive electronic rearrangement and bonding changes taking place along a reaction pathway. 32 − 42 During the BET analysis, only three types of bifurcation catastrophes have been found in chemical reactivity and two of them have been identified in the present study: the fold catastrophe, corresponding to the creation or annihilation of two critical points of different parity, and the cusp catastrophe, which transforms one critical point into three (and vice versa) such as in the formation or the breaking of a covalent bond.…”

“…Using the topology of the electron density, Krokidis and Silvi were the pioneers in the development of the theoretical background leading to the establishment of the bonding evolution theory (BET) in order to describe the molecular mechanism of a reaction in terms of creation or annihilation of electronic domains. , BET is a solid procedure based on the combination of the ELF , and Thom’s mathematical catastrophe theory (CT) . BET allows us to perceive electronic rearrangement and bonding changes taking place along a reaction pathway. − During the BET analysis, only three types of bifurcation catastrophes have been found in chemical reactivity and two of them have been identified in the present study: the fold catastrophe, corresponding to the creation or annihilation of two critical points of different parity, and the cusp catastrophe, which transforms one critical point into three (and vice versa) such as in the formation or the breaking of a covalent bond.…”

Intramolecular [3 + 2] Cycloaddition Reactions of Unsaturated Nitrile Oxides. A Study from the Perspective of Bond Evolution Theory (BET)

“…This represents an alternative to understand and describe chemical reactivity that is based on well-defined physical entities, such as electron density, ρ­( r ), which is measurable experimentaly due to the progress made in X-ray diffraction and spin-polarized neutron diffraction techniques . Within the QCT formalism, Krokidis et al proposed bonding evolution theory (BET), combining the electronic localization function (ELF) − and Thom’s Catastrophe Theory (CT) , to understand the chemical mechanism of organic reactions. − …”