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Anodic Reactivity of Alkyl S‑Glucosides
journal contribution
posted on 2022-04-13, 16:13 authored by Bhavesh Deore, Joseph E. Ocando, Lan D. Pham, Carlos A. SanhuezaA voltammetric study of a series
of alkyl and aryl S-glucosides unveiled the reactivity
patterns of alkyl S-glucosides toward anodic oxidation
and found noteworthy differences
with the trends followed by aryl derivatives. The oxidation potential
of alkyl S-glucosides, estimated herein from square-wave
voltammetry peak potentials (Ep), depends
on the steric properties of the aglycone. Glucosides substituted with
bulky groups exhibit Ep values at voltages
more positive than the values of those carrying small aglycones. This
relationship, observed in all analyzed alkyl series, is evidenced
by good linear correlations between Ep and Taft’s steric parameters (ES) of the respective alkyl substituents. Moreover, the role of the
aglycone’s steric properties as a primary reactivity modulator
is backed by poor correlations between Ep and the radical stabilization energies (RSEs) of the aglycone-derived
thiyl radicals (RS•). In contrast, aryl glucosides’ Ep values exhibit excellent correlations with
the aryl substituents’ Hammett parameters (σ+) and the
ArS• RSEs, evidencing the inherent stability of the reactive
radical intermediate as the primary factor controlling aryl glucoside’s
electrochemical reactivity. The reactivity differences between alkyl
and aryl S-glucosides also extend to the protective
group’s effect on Ep. Alkyl S-glucosides’ reactivity proved to be more sensitive
to protective group exchange.
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reactive radical intermediateradical stabilization energiesprotective group exchangederived thiyl radicalscarrying small aglyconesbulky groups exhibitsteric parameters (<protective group ’good linear correlationsfound noteworthy differencesrespective alkyl substituentsprimary reactivity modulatorars • rsesp sub sub >)>- glucosides unveiledanalyzed alkyl seriesaryl glucosides ’>- glucosidesreactivity differences>< subtaft ’steric propertiespoor correlationsglucosides substituted>‑ glucosidese reactivity patternselectrochemical reactivityanodic reactivityσ +)voltammetric studytrends followedrs •).oxidation potentialinherent stabilityestimated hereinaryl derivativesaglycone ’