Cogwheel effect in dialkyl disulfides

Nelander, Bengt; Sunner, Stig

doi:10.1021/ja00765a053

Cited by 23 publications

(11 citation statements)

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“…Disulfide bonds with different structures have been previously shown to undergo an exchange reaction triggered by the use of light, heat, a certain pH value, or a catalyst, leading to a partial conversion of two different reducible compounds (R 1 -S-S-R 1 and R 2 -S-S-R 2 ) into another new disulfide bond-containing molecule (R 1 -S-S-R 2 ) and further construction of a reversible dynamic balance system based on the aforementioned three structures. The well-documented cleavage of a disulfide link in either a homolytical or heterolytical way reveals (i) the generation of homolytical sulfenyl radicals with a relatively short life by homolytic scission via photolysis, oxidation, or heating and (ii) the production of heterolytical mercaptides (XS – ) or sulfenium cation (XS + ) under basic/nucleophilic or acidic/electrophilic , conditions by ionic scission. A subsequent reaction of the resulting sulfur radical, anion, or cation with another disulfide promotes the occurrence of further exchange reactions.…”

Section: Results and Discussionmentioning

confidence: 99%

Triple Functional AB₂ Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers

Liu

et al. 2020

ACS Biomater. Sci. Eng.

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Facile preparation of hyperbranched polymers (HPs) has been advanced tremendously by the use of either various multifunctional agent-mediated controlled living radical polymerizations or a highly reactive AB x unit-modulated self-stepwise polymerizations. However, it remains, to our knowledge, a significant challenge to prepare HPs with simultaneously precisely controlled degree of branching (DB) and biorelevant signal-triggered degradation property for controlled release applications due to the respective limitations of the aforementioned two strategies. For this purpose, a triple functional AB2 unit, A-SS-B2 chain transfer agent (AB2 CTA), that integrates the merits of both multifunctional agents and highly reactive AB x units was designed and synthesized successfully to include a disulfide bond for reduction-triggered polymer degradation toward promoted intracellular release of encapsulated cargoes, a trithiocarbonate group for a universal reversible addition-fragmentation chain transfer (RAFT) polymerization of any vinyl-based monomer, and three terminal groups consisting of one azide and two alkyne functions for the generation of hyperbranched topology via a self-click coupling-based polymerization. A subsequent self-click polymerization of the resulting AB2 CTA by click coupling in the presence of CuSO4·5H2O and sodium ascorbate (NaVc) generated a hyperbranched polymer template (HPT) with precisely modulated DB and a plurality of CTA units for a universal reversible addition-fragmentation chain transfer (RAFT) polymerization of any vinyl-containing monomer. The HPT was next used as a multimacro-CTA for RAFT polymerization of a typical hydrophilic monomer, oligo(ethylene glycol) monomethyl ether methacrylate (OEGMA), to demonstrate the potential of this HPT for a robust and facile production of bioreducible hyperbranched polymers for controlled release applications. The synthesized HPT-4-POEGMA can form unimolecular micelles with enhanced stability due to the hyperbranched structure, and the size of micelles varied in the range from 82.4 to 140.3 nm by a modulation of the molar feed ratio of monomer to HPT and polymerization time. More importantly, HPT-POEGMA micelles incubated with 10 mM glutathione (GSH) showed reduction-triggered cleavage of the disulfide links and polymer degradation for promoted intracellular doxorubicin (DOX) release and enhanced therapeutic efficiency. Taken together, this triple functional AB2 CTA provided a powerful means for the facile preparation of bioreducible hyperbranched polymers with precisely controlled DB for controlled release applications.

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Section: Results and Discussionmentioning

confidence: 99%

Triple Functional AB₂ Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers

Liu

et al. 2020

ACS Biomater. Sci. Eng.

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“…This species is again able to carry out the substitution at the original thiiranium or thiirenium ion, giving rise to the disulfide RSSR. Furthermore, the fast reequilibration among the three different disulfides catalyzed by the thiosulfonium salt and the competitive rearrangement of tert -butyl-substituted thiiranium ions to thietanium ions 8 or 9 and of tert -butyl-substituted thiirenium ions to thietium ions 10 have also to be considered. , Under the adopted reaction conditions (relatively high concentration of disulfide with respect to that of the substrate), only the rearrangements of trans thiiranium ions 1a , b and 3 (with a tert -butyl group cis to the substituent at sulfur) to thietanium ions 8a , b and 9 have been observed.…”

Section: Resultsmentioning

confidence: 99%

Nucleophilic Reactions at the Sulfur of Thiiranium and Thiirenium Ions. New Insight in the Electrophilic Additions to Alkenes and Alkynes. Evidence for an Episulfurane Intermediate

et al. 1999

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The thiiranium hexachloroantimonates 1a, 3, and 5a − c and the thiirenium hexachloroantimonates 6a − c and 7a with exocyclic S-R substituent (R = Me, Et, i-Pr) react at sulfur with dialkyl disulfides R‘ ‘SSR‘ ‘ (R‘ ‘ = Me, Et and R‘ ‘ ≠ R) in CD2Cl2 at 25 °C to give S-R‘ ‘ substituted ions. The reaction rates are affected by the steric hindrance of the substituents at sulfur and at ring carbons. t-2,t-3-Di-tert-butyl-r-1-methylthiiranium hexachloroantimonate (2) does not react, and the t-2-tert-butyl-c-3-phenyl-r-1-methylthiiranium (5a) reacts about 100 times faster than the c-2,t-3-di-tert-butyl-r-1-methylthiiranium ion (1a). The analysis of the kinetic data suggests that the sulfonium sulfur undergoes attack by the disulfide in the ring plane from a direction that is parallel to the C−C ring bond. This is also the direction which ensures the maximum overlap with the LUMO of thiiranium or thiirenium ions (determined at the RHF/3-21G*//RHF/3-21G* level). The combined consideration of the approach modality and of the maximum orbital overlap suggests that the nucleophilic substitution at sulfonium sulfur is not an SN2-like reaction but occurs via an intermediate with episulfurane-like structure. The principle of microscopic reversibility will dictate that this is also the first intermediate in the electrophilic sulfenylation of unsaturated C−C bonds.

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“…Dialkyl disulfides give nearly statistical distributions with K = 4 (eq 14) except when zerZ-butyl groups are involved, for which K ~25. 28,29 The high values herein observed are attributable to steric constraints imposed by the bulky dimer fragment. Equilibrium was never attained in the allotted times for the SMo2SSR, R = Et and Bz, derivatives.…”

Section: Discussionmentioning

confidence: 80%

S-S photohomolysis at dimolybdenum(V) RSS- and S22- bridges

Noble¹

1987

Inorg. Chem.

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Figure 2. Schematic reaction coordinate for the approach of the anionic quencher A toward Cu(dmp)2+. (Charges are omitted for clarity.) The lower curve represents the ground state, where a shallow minimum occurs due to outer-sphere complex formation. The upper curve represents the CT excited state, in which the anion moves in close enough to form an inner-sphere complex. The wiggly arrows indicate the relative energies associated with the nonradiative decay process at two locations along the reaction coordinate. explained because the bulky phenyl substituents interfere with formation of the five-coordinate adduct.30The reaction coordinate diagram in Figure 2 indicates why association of a fifth donor can result in quenching of the excited state. From left to right, the reaction coordinate is constructed such that the center-to-center distance between the copper and the anion increases. Also implicit in the coordinate is the internal

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Cogwheel effect in dialkyl disulfides

Cited by 23 publications

References 1 publication

Triple Functional AB₂ Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers

Triple Functional AB₂ Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers

Nucleophilic Reactions at the Sulfur of Thiiranium and Thiirenium Ions. New Insight in the Electrophilic Additions to Alkenes and Alkynes. Evidence for an Episulfurane Intermediate

S-S photohomolysis at dimolybdenum(V) RSS- and S22- bridges

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Cogwheel effect in dialkyl disulfides

Cited by 23 publications

References 1 publication

Triple Functional AB2 Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers

Triple Functional AB2 Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers

Nucleophilic Reactions at the Sulfur of Thiiranium and Thiirenium Ions. New Insight in the Electrophilic Additions to Alkenes and Alkynes. Evidence for an Episulfurane Intermediate

S-S photohomolysis at dimolybdenum(V) RSS- and S22- bridges

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Triple Functional AB₂ Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers

Triple Functional AB₂ Unit-Modulated Facile Preparation of Bioreducible Hyperbranched Copolymers