In Pursuit of Stable, Strained Smallring Sulfur Heterocycles

Zoller, Uri

doi:10.1080/01961779708047919

Cited by 7 publications

(2 citation statements)

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“…This exoperoxide undergoes autoxidation cleavage, turning the peroxide into the hydroxy group. The resulting intermediate, 2-hydroxy-2-phenyl-4-thioxochroman-3-one, undergoes another oxidation step on the sulfur atom with triplet oxygen via a 1,2,3-thiadioxetane intermediate, analogous to the reactions between thiones and 1 O 2 . , This mechanism finally leads to the formation of 2-hydroxy-3,4-flavandione ( 34 ), identified as a final product. 2-Hydroxy-3,4-flavandione derivatives have already been reported in the literature as the products obtained from 3-hydroxyflavone derivatives by chemical oxidation and photolysis .…”

Section: Resultsmentioning

confidence: 99%

Structure–Photoreactivity Relationship Study of Substituted 3-Hydroxyflavones and 3-Hydroxyflavothiones for Improving Carbon Monoxide Photorelease

Jézéquel,

Svěrák,

Ramundo

et al. 2024

J. Org. Chem.

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Carbon monoxide (CO) is notorious for its toxic effects but is also recognized as a gasotransmitter with considerable therapeutic potential. Due to the inherent challenges in its delivery, the utilization of organic CO photoreleasing molecules (photo-CORMs) represents an interesting alternative to CO administration characterized by high spatial and temporal precision of release. This paper focused on the design, synthesis, and photophysical and photochemical studies of 20 3-hydroxyflavone (flavonol) and 3hydroxyflavothione derivatives as photoCORMs. Newly synthesized compounds bearing various electron-donating and electron-withdrawing groups show bathochromically shifted absorption maxima and considerably enhanced CO release yields compared to the parent unsubstituted flavonol, exceeding 0.8 equiv of released CO in derivatives exhibiting excited states with a charge-transfer character. Until now, such outcomes have been limited to flavonol derivatives possessing a π-extended aromatic system. In addition, thione analogs of flavonols, 3-hydroxyflavothiones, show substantial bathochromic shifts of their absorption maxima and enhanced photosensitivity but provide lower yields of CO formation. Our study elucidates in detail the mechanism of CO photorelease from flavonols and flavothiones, utilizing steady-state and timeresolved spectroscopies and photoproduct analyses, with a particular emphasis on unraveling the structure−photoreactivity relationship and understanding competing side processes.

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Section: Resultsmentioning

confidence: 99%

Structure–Photoreactivity Relationship Study of Substituted 3-Hydroxyflavones and 3-Hydroxyflavothiones for Improving Carbon Monoxide Photorelease

Jézéquel,

Svěrák,

Ramundo

et al. 2024

J. Org. Chem.

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“…[2][18] § 'Schwefelammon' means literally NH 4 HS and (NH 4 ) 2 S; the sulfidation reactions described [16] leave no doubt, however, that the rather unstable compound NH 4 HS had become oxidized to the polysulfide, at least partially, before or during the reaction, fortuitously or on purpose. S N Ad Due to our current interest in reactions involving thiaziridines as intermediates, we decided to repeat the experiment reported by v. Miller and Plöchl [16] with the aim of proving unequivocally the structure of the crystalline reaction product, whose identity so far rests on its elemental composition only.…”

Section: Methodsmentioning

confidence: 99%

Sulfur addition to aldimines: thioamides, not thiaziridines, as products; revision of an old report

Mlostoń

Depczyński

Woznicka

et al. 2005

Journal of Sulfur Chemistry

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The Ramberg‐Bäcklund Reaction

Taylor

Casy

2003

Organic Reactions

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The base‐mediated conversion of alpha‐halosulfones into region‐defined alkenes was first described by Ludwig Ramberg and Birger Backlund. This transformation has proved to be of wide synthetic value and is known as the Ramberg‐Backlund reaction (RBR). The facile nature of the RBR is surprising given the difficulties encountered when attempting to carry out nucleophilic substitution reactions on alpha‐halosulfones. In contrast to halogens adjacent to carbonyls and related electron‐withdrawing groups, polar, steric and field effects appear to combine leading to the marked deactivation of alpha‐halosulfones. The stereochemical outcome of the reaction was also unexpected: a predominance of Z‐alkenes is often observed with relatively weak bases, whereas stronger bases tend to favor E‐alkenes. The mechanism of the RBR was therefore the subject of intense interest, particularly in the 1950s and 1960s. From the synthetic viewpoint, the RBR is attractive for a number of reasons, for example, the accessibility of the precursor sulfide and sulfones; the conjunctive nature of the process; the unambiguous location of the resulting double bonds, among others. Organic sulfones are readily available, but the preparation of alpha‐halosulfones can be problematic. In view of this, perhaps the most significant synthetic advance concerning RBR has been the development of Meyer's modification, which involves in‐situ halogenation‐RBR sequence and enables sulfones to be converted directly into alkenes. This chapter discusses the mechanism of RBR, its scope and limitations, applications of the reaction in natural product synthesis, and comparison of the RBR with related procedures. Representative experimental procedures are also given.

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In Pursuit of Stable, Strained Smallring Sulfur Heterocycles

Cited by 7 publications

References 61 publications

Structure–Photoreactivity Relationship Study of Substituted 3-Hydroxyflavones and 3-Hydroxyflavothiones for Improving Carbon Monoxide Photorelease

Structure–Photoreactivity Relationship Study of Substituted 3-Hydroxyflavones and 3-Hydroxyflavothiones for Improving Carbon Monoxide Photorelease

Sulfur addition to aldimines: thioamides, not thiaziridines, as products; revision of an old report

The Ramberg‐Bäcklund Reaction

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