Active Role of Hydrogen Bonds in Rupe and Meyer−Schuster Rearrangements

Abstract

Rupe and Meyer-Schuster rearrangements for the R2C(OH) [Formula: see text] C⋮C [Formula: see text] H + H3O(+) and (H2O)9 model (R = methyl and phenyl groups) have been investigated by the use of density functional theory calculations. In the substrate R2C(OH) [Formula: see text] C⋮CH catalyzed by H3O(+)(H2O), three reaction channels, the two rearrangements and SN (nucleophilic substitution), were predicted by the frontier molecular orbital theory. The SN (the OH-group exchange) path was found to have a large activation energy. For 2-methylbut-3-yn-2-ol (R = Me), the Rupe rearrangement has been found to be much more favorable than the Meyer-Schuster rearrangement. For 1,1-diphenylprop-2-yn-1-ol (R = Ph), the occurrence of Meyer-Schuster rearrangement is very likely with the small activation energy. Both rearrangements do not involve the carbonium ion intermediates. However, the calculated geometries of the first transition state are carbonium-ion-like. Dehydration and hydration may occur via the intermolecular proton relay along the hydrogen-bond chains. Minimal models were proposed to represent reaction mechanisms of both rearrangements.

An Energy Investigation into 1D/2D Oriented‐Attachment Assemblies of 1D Ag Nanocrystals

“…So it seems that traces of water are important to achieve the Meyer–Schuster step, which is consistent with the fact that this reaction relies on a concerted process involving several hydrogen‐bonded water molecules, and does not involve a carbonium intermediate 17. Furthermore, it seems that the ambident reactivity of the intermediate calcium enolate (C‐ or O‐addition) can be controlled by the reaction conditions.…”