Electrochemical Bromination of Peracetylated Glycals

Čolović, Marija; Vukićević, Mirjana; Šegan, Dejan; Manojlović, Dragan; Šojić, Nešo; Somsák, László; Vukićević, Rastko D.

doi:10.1002/adsc.200700310

Cited by 12 publications

(4 citation statements)

References 24 publications

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“…Although anodic and PET oxidations of enol ethers are of significant synthetic interest, their oxidation potentials are not well established. , Besides oxidative DNA damage via nucleotide radical cations, whose kinetics has been thoroughly studied, the oxidation potential of only one glycal, i.e., tri- O -acetyl- d -glucal ( 1a ), has been described until now . Therefore, we investigated the redox behavior of various glycals 1 by CV (Table ) .…”

Section: Resultsmentioning

confidence: 99%

Remarkable Oxidation Stability of Glycals: Excellent Substrates for Cerium(IV)-Mediated Radical Reactions

et al. 2008

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Abstract:The remarkable stability of glycals under oxidative conditions becomes apparent by their redox data in solution, computed HOMO energies, and behavior on the addition of electrophilic radicals generated in the presence of cerium(IV) ammonium nitrate. Oxidation potentials up to 2.03 V vs ferrocene were obtained, which are exceptionally high for cyclic enol ethers but correlate nicely with the reaction times of the radical reactions. Protecting groups have a strong influence on the oxidation stability and HOMO energies of glycals as E ox is shifted from O-silyl over O-benzyl to O-acetyl by more than 500 mV. Interestingly, this effect must be transmitted through σ-bonds, even up to the para-position of a benzoate group, as verified by a wide variation of remote substituents in the carbohydrate. Favorable interactions of the σ*-orbital of the adjacent C-O bond with the HOMO of the double bond are proposed as a mechanistic rationale, which might be important for the redox behavior of other allylic systems. Finally, donors and acceptors in the 1-position exert the strongest influence on the oxidation stability, shifting the potentials by almost 1 V and resulting in different follow-up reactions of the cerium(IV)-mediated additions of malonates. It is the remarkable oxidation stability of glycals that makes them valuable building blocks in carbohydrate chemistry.

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Section: Resultsmentioning

confidence: 99%

Remarkable Oxidation Stability of Glycals: Excellent Substrates for Cerium(IV)-Mediated Radical Reactions

et al. 2008

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“…The bromination of peracetylated glycals with electrochemically generated tribromide was found to give predominantly the products of anti-addition of bromine from the C-6 side in high yields. 31 A general method for the introduction of the relatively unknown difluoromethylenedioxy group (-OCF 2 O-) has been reported. 32 Treatment of alcohols, diols and cathecols with thiophosgene followed by BrF 3 leads to bis(alkoxy)difluoromethane and difluorodioxolane derivatives.…”

Section: Interhalogens and Polyhalidesmentioning

confidence: 99%

Halogens and noble gases

Justik

2009

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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This chapter provides a digest of the literature reported during 2008 concerning the elemental halogens and noble gases as well as compounds containing these elements in their positive oxidation states. The intent is to highlight discovery and provide insight into current research trends. HighlightsThe 2008 literature for halogen chemistry is highlighted by the first iodonium(V) salt with an electrophilic cation and the first crystallographic evidence for the BrO 2 + cation. Noble gas chemistry advances include the first preparation of HXeOXeH, the smallest known neutral molecule containing two noble gas atoms and the synthesis of [F 5 SN(H)Xe][AsF 6 ] which exhibits one of the shortest Xe-N bonds yet observed. HalogensRecent reviews reflect the importance of organo-fluorine compounds in modern medicinal chemistry. The first offers perspective into the effect of fluorine incorporation into potential drug candidates. 1 The second provides a more directed review of the application of 19 F NMR techniques to elucidate the mechanistic fate of fluoropharmaceuticals in biological systems. 2 Lastly, the recent applications of fluorinated organophosphate chemistry including synthetic methods have been systematically reviewed. 3 With these applications in mind, the fluorination of organic molecules continues to engage researchers. Elemental fluorine was found to react selectively with the tertiary sites of 3b-acetoxy-5a-androstan-17-one to afford three mono-fluorinated products while Selectofluor s exhibited preference for the fluoridation of secondary sites. 4 The reaction of Selectofluor s with acetonide-protected bis-allylsilane results in the diastereoselective preparation of a 3,6-difluorinated-1,7-dienes, key intermediates in the synthesis of novel deoxyfluoro-myo-inositols. 5 Treatment with Selectofluor s of 1,5-anhydro-2-deoxy-hex-1-enitol derivatives has found application in the preparation of chiral 1-fluoro-1-halo-1-iodo-alditols. 6 With the increasing use of fluorous solid phase extraction (FSPE) techniques for the purification of 18 F-labelled radiotracers, significant attention has been focused on tagging and detagging strategies. In the first known detagging process relying on C-H bond formation, fluorous allylsilanes were prepared by cross-metathesis and subsequently subjected to electrophilic fluorodesilylation with Selectfluor s and the resulting allylic fluorides were successfully purified by FSPE. 7 For the first time gold catalysis

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“… [26] Dibromination on per acetylated glycals was also achieved by using NBS/DMSO in DCM (Figure 1b), [27] and an electrochemical approach with elemental bromine (Figure 1c). [28] Bromination of indole was carried by different reagent systems such as by utilizing diacetoxyiodobenzene and NaBr (Figure 1d), [29] tetra butyl ammonium bromide/ammonium bromide (1 : 1 equiv) with 2 mA electricity (Figure 1e), [30] and N‐chloro‐N‐fluorobenzenesulfonylamide (CFBSA), potassium bromide (Figure 1f). [31] There are numerous methods to compose halogenated scaffolds from heterocyclic compounds [32–34] .…”

Section: Introductionmentioning

confidence: 99%

TBA−Br and Selectfluor Mediated Bromination of Glycals and Heterocyclic Compounds: Substrate Scope and Synthetic Utility

Maheshwari,

Hussain

2023

ChemistrySelect

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Herein, we have devised a metal‐free stereoselective protocol mediated by selectfluor for the dibromination of sugar enol‐ethers and monobromination of heterocyclic compounds. The dibromination of glycals was achieved within 5 minutes at room temperature with excellent yields. The tolerance of various protecting groups such as acetyl, benzyl, and silyl in sugars was checked. When the same reagent system was applied to substituted indoles and chromones 3‐brominated products were obtained but at elevated temperatures. The synthetic utility of the methodology was demonstrated by using the brominated indoles and chromones to synthesize the 3‐aryl indoles and isoflavones respectively via Suzuki‐Miyura cross‐coupling reactions.

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Electrochemical Bromination of Peracetylated Glycals

Cited by 12 publications

References 24 publications

Remarkable Oxidation Stability of Glycals: Excellent Substrates for Cerium(IV)-Mediated Radical Reactions

Remarkable Oxidation Stability of Glycals: Excellent Substrates for Cerium(IV)-Mediated Radical Reactions

Halogens and noble gases

TBA−Br and Selectfluor Mediated Bromination of Glycals and Heterocyclic Compounds: Substrate Scope and Synthetic Utility

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