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

Abstract

This study is focused on describing the molecular mechanism beyond the molecular picture provided by the evolution of molecular orbitals, valence bond structures along the reaction progress, or conceptual density functional theory. Using bonding evolution theory (BET) analysis, we have deciphered the mechanism of the 1,3-dipolar rearrangement between acetonitrile oxide and (1 S ,2 R ,4 S )-2-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate derivatives. The BET study revealed that the formation of the C–C bond takes place via a usual sharing model before the O–C one that is also formed in the halogenated species through a not very usual sharing model. The mechanism includes depopulation of the electron density at the N–C triple bond and creation of the V(N) and V(C) monosynaptic basins, depopulation of the former C–C double bond with the creation of V(C,C) basins, and final formation of the V(O,C) basin associated with the O–C bond. The topological changes along the reaction pathway take place in a highly synchronous way. BET provides a convenient quantitative method for deriving curly arrows and electron flow representation to unravel molecular mechanisms.

Density Functional Theory Calculations: A Useful Tool to Investigate Mechanisms of 1,3-Dipolar Cycloaddition Reactions

“…The 1,3-dipolar rearrangement involving acetonitrile oxide 42 and (1S,2R,4S)-2-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate derivatives 43a-c was studied, and a BET (bonding evolution theory) analysis was conducted [38]. Optimizations were performed at the ωB97X-D/6-311G(d) level of calculations.…”

“…In fact, nitrile oxide 42 reacts with the oxanorbornenic compounds 43a-c through syn or anti-attacks and para and meta regioisomeric approaches of nitrile oxide on 7-oxanorbornenic derivatives (Scheme 16). The 1,3-dipolar rearrangement involving acetonitrile oxide 42 and (1S,2R,4S)-2-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate derivatives 43a-c was studied, and a BET (bonding evolution theory) analysis was conducted [38]. Optimizations were performed at the ωB97X-D/6-311G(d) level of calculations.…”

One-to-One Correspondence between Reaction Pathways and Reactive Orbitals

“…The relationship between the potential energy theory and the electronic theory has, so far, been rarely considered despite the common objective of reaction analyses. Many studies have focused on electron transfer in reactions following the variation of electronic distributions and molecular orbitals. − However, these studies have not discussed the direct relationship between these theories. Reactive orbital energy theory , was developed to extend the electronic theories using the quantitative occupied and unoccupied valence orbital energies that LC-DFT enables us to calculate for the first time. , Applying this theory to IRCs, the pair of occupied and unoccupied reactive orbitals, which mainly drive the reactions, are determined as the occupied and unoccupied valence orbitals giving the most stabilized and most destabilized orbital energies during the processes along the IRCs, respectively.…”

On the Nature of Bonding in the Photochemical Addition of Two Ethylenes: C-C Bond Formation in the Excited State?

“…37 The usefulness of the ELF to describe bonding is certainly probed and spread several areas of chemistry. 38,39 The topological analysis of ELF yields a division of molecular space into basins of attractors that enable a convenient association of the electronic molecular structure with chemical concepts inherent to the Lewis-like theory of bonding and related concepts. 36,40,41 It is important to emphasize that in such a context, bonding in real space becomes structurally represented in terms of the shape of the electron localization pairs and the electron density (i.e., via basin populations).…”

“…In particular, key bonding events (e.g., bond formation and bond-breaking), as well as the electron rearrangement along any chemical reaction, can be suitably represented by a sequence of ELF-based molecular configurations (ELF-MG) separated by abrupt changes in the shape of electron pair delocalization. 39,[42][43][44] In this work, we…”