NDLI: Assessing the reactivity of sodium alkyl-magnesiates towards quinoxaline: single electron transfer (SET) vs. nucleophilic alkylation processes

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Carrella, Luca M. Clegg, William Livingstone, Zoe Hernán-gómez, Alberto Baillie, Sharon E. Armstrong, David R. Hevia, Eva Kennedy, Alan R. Harrington, Ross W. Rentschler, Eva
Description	Author Affiliation: Livingstone Z ( WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK. eva.hevia@strath.ac.uk.)
Abstract	By exploring the reactivity of sodium butyl-magnesiate (1) supported by the bulky chelating silyl(bisamido) ligand $\{Ph_{2}Si(NAr)_{2}\}^{2−}$ (Ar = $2,6-iPr_{2}-C_{6}H_{3})$ towards Quinoxaline (Qx), the ability of this bimetallic system to effectively promote SET processes has been disclosed. Thus 1 executes the single-electron reduction of Qx affording complex (2) whose structure in the solid state contains two quinaxolyl radical anions Qx˙ stabilised within a dimeric magnesiate framework. Combining multinuclear NMR and EPR measurements with DFT calculations, new insights into the constitution of 2 in solution and its magnetic behaviour have been gained. Further evidence on the SET reactivity of 1 was found when it was reacted with nitroxyl radical TEMPO which furnished contacted ion pair sodium magnesiate $[(Ph_{2}Si(NAr)_{2})Mg(TEMPO^{−})Na(THF)_{3}]$ (4) where both metals are connected by an alkoxide bridge, resulting from reduction of TEMPO. The role that the different ligands present in 1 can play in these new SET reactions has also been assessed. Using an amination approach, the Bu group in 1 can be replaced by the more basic amide TMP allowing the isolation of (3) which was characterised by multinuclear NMR and X-ray crystallography. $^{1}H$ NMR monitoring of the reaction of 3 with Qx showed its conversion to 2, leaving the hydrogen atoms of the heterocycle untouched. Contrastingly, using sodium homoalkyl magnesiate $[NaMg(CH_{2}SiMe_{3})_{3}]$ (5) led to the chemoselective C2 alkylation of this heterocycle, suggesting that the presence of the steric stabiliser $\{Ph_{2}Si(NAr)_{2}\}^{2−}$ on the mixed-metal reagent is required in order to facilitate the Qx reduction.
ISSN	14779226
Issue Number	14
Journal	Dalton Trans.
Volume Number	45
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2016-04-14
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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