Theoretical Prediction of a Base-Catalyzed Bicyclic Boulton−Katritzky Rearrangement

Abstract

On the basis of quantum chemical calculations, the bicyclic Boulton--Katritzky rearrangement (BKR) has been classified as a pseudopericyclic reaction. Theoretical investigations extend the applicability of the BKR to classes of molecules other than those known from experiments.

Synthesis and reactivity of heterocyclic hydroxylamine-O-sulfonates

“…To some extent, the electrophilic amination reactions of anions J (Scheme 8), K (Scheme 9), and M (Scheme 10) presented above resemble the previously investigated S N 2 reactions at sp 2 -hybridized carbon [57][58][59][60][61][62][63] or nitrogen [64] atoms, as well as the Boulton-Katritzky rearrangement [65,66]. Thus, the substitution of the sulfate leaving group by an amidate or thioamidate anion may proceed according to either the S N 2π mechanism (out-of-plane nucleophilic attack) by interacting with the π orbital of the imino group, or S N 2σ mechanism (in-plane attack) where a nucleophile interacts with the σ orbital of the imino nitrogen atom (Figure 9).…”

The nature of bonding in pericyclic and pseudopericyclic transition states: Thermal chelotropic decarbonylations

“…[1][2][3][4][5][6][7][8][9][10][11] In this context, it has been pointed out that the fundamental difference among these two topologies is the conservation or not of a cyclic orbital overlap between the orbitals involved in bonding changes at the transition state. Henceforth, the lack of orbital overlap in a pseudopericyclic reaction has significant implications in the global ͑i.e., ther-modynamic͒ and local ͑i.e., selectivity͒ chemistry of these systems.…”

Synthesis of Heterocycles by Intramolecular Nucleophilic Substitution at an Electron‐Deficient sp2 Nitrogen Atom

“…Several reports have been published on such processes including those of Narasaka and co-workers who found that substitution at the nitrogen atom of O-protonated oximes may occur easily in an S N 2 manner. [40] Moreover, based on the knowledge of heterocyclic chemistry, the well-known Boulton-Katritzky rearrangement can formally be written as an intramolecular nucleophilic substitution that proceeds according to a unimolecular one-step mechanism, [41][42][43][44] which, in turn, bears a resemblance to the recently investigated vinylic S N 2 reactions at carbon atoms. [45][46][47][48][49][50][51] On the basis of this knowledge, substitution of the sulfate leaving group by the amidate anion at the sp 2 -hybridized N2 nitrogen atom in 2 may proceed either by an S N 2π mechanism (out-of-plane nucleophilic attack) by interacting with the π* orbital of the imino group or by an S N 2σ mechanism (in-plane attack) in which the nucleophile interacts with the σ* orbital of the imino nitrogen of the N-O bond (Scheme 7).…”