Anodic Reactivity of Alkyl S‑Glucosides

• Published in: Journal of organic chemistry 2022-05, Vol.87 (9), p.5952-5960
• Main Authors: Deore, Bhavesh, Ocando, Joseph E, Pham, Lan D, Sanhueza, Carlos A
• Format: Article
• Language: English
• Subjects: Electrodes; Glucosides; Oxidation-Reduction
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/acs.joc.2c00222

A 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 (E p), depends on the steric properties of the aglycone. Glucosides substituted with bulky groups exhibit E p 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 E p and Taft’s steric parameters (E S) 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 E p and the radical stabilization energies (RSEs) of the aglycone-derived thiyl radicals (RS•). In contrast, aryl glucosides’ E p 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 E p. Alkyl S-glucosides’ reactivity proved to be more sensitive to protective group exchange.