Generation of ortho-quinone methides upon thermal extrusion of sulfur dioxide from benzosultones

Wojciechowski, Krzysztof; Dolatowska, Karolina

doi:10.1016/j.tet.2005.06.087

Cited by 27 publications

(11 citation statements)

References 16 publications

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“…Apart from their involvement in biological processes, o ‐QMs are also very versatile intermediates in organic synthesis [119–124], but until now they have been less utilized in total syntheses [125]. Since they are ephemeral species [126], they must be generated in situ by processes that involve photolysis of o ‐, m ‐, or p ‐hydroxybenzyl alcohols [127], thermal reactions [128, 129], thermal extrusion of sulfur dioxide [128] and anionic triggered reactions [130, 131]. In this regard, Amouri et al .…”

Section: O‐quinone Methides: Generalitymentioning

confidence: 99%

Syntheses of chromenes and chromanes via o‐quinone methide intermediates

Ferreira

Silva

Pinto

et al. 2009

Journal of Heterocyclic Chem

126

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Section: O‐quinone Methides: Generalitymentioning

confidence: 99%

Syntheses of chromenes and chromanes via o‐quinone methide intermediates

Ferreira

Silva

Pinto

et al. 2009

Journal of Heterocyclic Chem

126

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“…Keywords: arylboronic esters · H 2 O 2 induction · quinone methides · substitutent effects · trapping in situ have been reported. [18][19][20][21][22][23][24][25][26][27][28][29][30][31] Very few systematic studies have been performed on the formation of QMs from different precursors (QMP). Rokita et al have reported that the formation of QMs from fluoride-cleavable precursors are strongly dependent on the leaving group attached to the benzylic position of their precursor.…”

Section: Introductionmentioning

confidence: 99%

Substituent Effects on Oxidation‐Induced Formation of Quinone Methides from Arylboronic Ester Precursors

Cao

Christiansen

Peng

2013

Chemistry A European J

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A series of arylboronic esters containing different aromatic substituents and various benzylic leaving groups (Br or N(+)Me3Br(-)) have been synthesized. The substituent effects on their reactivity with H2O2 and formation of quinone methide (QM) have been investigated. NMR spectroscopy and ethyl vinyl ether (EVE) trapping experiments were used to determine the reaction mechanism and QM formation, respectively. QMs were not generated during oxidative cleavage of the boronic esters but by subsequent transformation of the phenol products under physiological conditions. The oxidative deboronation is facilitated by electron-withdrawing substituents, such as aromatic F, NO2, or benzylic N(+)Me3Br(-), whereas electron-donating substituents or a better leaving group favor QM generation. Compounds containing an aromatic CH3 or OMe group, or a good leaving group (Br), efficiently generate QMs under physiological conditions. Finally, a quantitative relationship between the structure and activity has been established for the arylboronic esters by using a Hammett plot. The reactivity of the arylboronic acids/esters and the inhibition or facilitation of QM formation can now be predictably adjusted. This adjustment is important as some applications may benefit and others may be limited by QM generation.

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“…Compounds 10a-f were prepared by refluxing of the mixture of corresponding benzosultones 7a-f and appropriately substituted maleimides 9 in chlorobenzene [2].…”

Section: Methodsmentioning

confidence: 99%

“…These compounds were obtained in a [4 + 2] ଝ Part of this work was presented during 38 Jahrestagung der Deutschen Gesellschaft für Massenspektrometrie (DGMS) cycloaddition of N-substituted maleimides 9 to orthomethylenequinones 8 generated via thermal extrusion of SO 2 from 3H-1,2-benzoxathiole 2,2-dioxides 7 (benzosultones; Scheme 3) [2]. The latter species seem to be important intermediates in chemical and biochemical reaction pathways as it has been reviewed recently [3].…”

Section: Introductionmentioning

confidence: 99%