New Insights into the Substituents’ Effect on the Formation and Dissociation of Radical Anions: Dissociative Electron Transfer to Arylsulfonylphthalimides

Abstract

The electrochemical reduction of a series of biologically relevant p‐substituted arylsulfonylphthalimides was investigated and the results were analysed using theoretical calculations and application of Savéant's dissociative electron transfer theory. The dissociation rate constants of the radical anion intermediates were calculated and showed that upon changing the substituent from the MeO, to Me, H, F, Cl and CN the dissociation became faster. A good correlation with the Hammett substituent constants was also obtained. With the NO2 substituent the trend was however inversed. These results and the electrolysis data showed that the dissociation involves the N−S chemical bond. Theoretical calculations showed that for all investigated compounds the extra electron was hosted by the phthalimidyl group except for the p‐NO2 substituted compound for which the extra electron was hosted by the nitrophenyl moiety. Thermodynamic considerations showed that the dissociation of the radical anion of the p‐NO2 compound followed a heterolytic cleavage whereas those of the rest of the investigated compounds followed a homolytic cleavage. The above intriguing result was rationalized through application of the extension of Savéant's dissociative electron transfer theory to the decomposition of radical anions. This study is important not only for understanding substituents’ effect on the biological activity of these compounds but also on the formation and dissociation of radical anions in general.

Metal‐ and Catalyst‐Free Synthesis of 2‐Substituted‐Phthalimides Using 2‐(Arenesulfonyl)Phthalimide as Key Reagents

“…Benzenesulfonyl phthalimide ( 3 a ) and toluenesulfonyl phthalimide ( 3 b ) were prepared in good yields following a slightly modified reported methodology [18] (Scheme 1). Reaction conditions were identical for the preparation of compounds 5 a and 5 b (Scheme 2).…”

“…Melting points are General procedure for the preparation of N-substituted arenesulonyl phthalimides (3) and arenesulfonyl succinimide (5): Prepared by modification of reported methodology. [18,21,24,25,29] In a dry flask, a mixture of arenensulfonyl chloride (1 equiv., 30.98 mmol,)…”

“…General procedure for the preparation of N ‐substituted arenesulonyl phthalimides (3) and arenesulfonyl succinimide (5) : Prepared by modification of reported methodology [18,21,24,25,29] . In a dry flask, a mixture of arenensulfonyl chloride (1 equiv., 30.98 mmol,) and imide (1.1 Equiv., 33.98 mmol,) in acetonitrile (150 mL) was cooled to 0 °C in an ice bath for 30 min under nitrogen.…”

“…Although the synthesis of arenesulfonyl phthalimide derivatives from phthalimide and the corresponding arenesulfonyl chloride is easy, [18,19] only a few studies are found to explore the chemical scope of arenesulfonyl phthalimide compounds. [20][21][22][23] Kurtuk and Ozturk studied the reaction of arenesulfonyl phthalimides with amines and proposed the formation of a product, though its characterization was not reported.…”

Mesolysis of an asymmetric diphenyldisulfide radical anion studied by γ-ray and pulsed-electron radiolyses

“…A similar substituent effect on the mesolysis of N -(phenylsulfonyl)phthalimides radical anions which undergo N–S bond cleavage was investigated by using electrolysis techniques. 31 The dissociation rate of the radical anion with the CN group was evaluated to be greater than that with an MeO group.…”