Sodiated Oppolzer Enolates: Solution Structures, Mechanism of Alkylation, and Origin of Stereoselectivity

NMR spectroscopic studies reveal camphorsultam-derived sodium enolates known as Oppolzer enolates reside as monomers in neat THF and THF/HMPA solutions and as dimers in toluene when solvated by -tetramethylethylenediamine (TMEDA) and -pentamethyldiethylenediamine (PMDTA). Density functional theory (...

Full description

Saved in:
Bibliographic Details
Published in:Organic chemistry frontiers an international journal of organic chemistry 2023-09, Vol.10 (19), p.4750-4757
Main Authors: Lui, Nathan M, Collum, David B
Format: Article
Language:English
Subjects:
Alkylation
Camphor
Density functional theory
Ion pairs
Monomers
NMR
Nuclear magnetic resonance
Organic chemistry
Solvation
Stereoselectivity
Toluene
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:NMR spectroscopic studies reveal camphorsultam-derived sodium enolates known as Oppolzer enolates reside as monomers in neat THF and THF/HMPA solutions and as dimers in toluene when solvated by -tetramethylethylenediamine (TMEDA) and -pentamethyldiethylenediamine (PMDTA). Density functional theory (DFT) computations attest to the solvation numbers. Rate studies show analogy with previously studied lithiated Oppolzer enolates in which alkylation occurs through non-chelated solvent-separated ion pairs. The origins of the selectivity trace to transition structures in which the alkylating agent is guided to the face of the camphor owing to stereoelectronic preferences imparted by the sultam sulfonyl moiety. Marked secondary-shell solvation effects are gleaned from the rate studies.
ISSN:2052-4110
2052-4110
DOI:10.1039/d3qo01021j