Convenient and Efficient Method for the Iodination of Aromatic Amines by Pyridinium Iodochloride

Khansole, Sandeep V.; Junne, Subhash B.; Sayyed, Mudassar A.; Vibhute, Yeshwant B.

doi:10.1080/00397910801989659

Cited by 11 publications

(5 citation statements)

References 21 publications

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“…All of the parent ortho ‐haloanilines of N‐ formyl‐ ortho ‐iodoanilines 1 are commercially available, although some were prepared by standard aromatic bromination37 or iodination38 methods. N ‐Formylanilines 1 b and 1 i were purchased from commercial sources, and the other N ‐formylanilines were obtained by N ‐formylation of the corresponding ortho ‐haloanilines with formic acid following a literature procedure 39.…”

Section: Methodsmentioning

confidence: 99%

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Gao

Back

2012

Chemistry A European J

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A versatile new synthesis of indoles was achieved by the conjugate addition of N-formyl-2-haloanilines to acetylenic sulfones, ketones, and esters followed by a copper-catalyzed intramolecular C-arylation. The conjugate addition step was conducted under exceptionally mild conditions at room temperature in basic, aqueous DMF. Surprisingly, the C-arylation was performed most effectively by employing copper(II) acetate as the catalyst in the absence of external ligands, without the need for protection from air or water. An unusual feature of this process, for the case of acetylenic ketones, is the ability of the initial conjugate-addition product to serve as a ligand for the catalyst, which enables it to participate in the catalysis of its further transformation to the final indole product. Mechanistic studies, including EPR experiments, indicated that copper(II) is reduced to the active copper(I) species by the formate ion that is produced by the base-catalyzed hydrolysis of DMF. This process also served to recycle any copper(II) that was produced by the adventitious oxidation of copper(I), thereby preventing deactivation of the catalyst. Several examples of reactions involving acetylenic sulfones attached to a modified Merrifield resin demonstrated the feasibility of solid-phase synthesis of indoles by using this protocol, and tricyclic products were obtained in one pot by employing acetylenic sulfones that contain chloroalkyl substituents.

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Section: Methodsmentioning

confidence: 99%

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Gao

Back

2012

Chemistry A European J

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“…PyICl does not interfere with the diagnostic signals from the product 8 as its signals appear at almost the same position as those from pyridine itself. If PyICl signals became problematic, then we could ameliorate this problem by using pyridine-d 5 to prepare perdeuterated PyICl . The ready ability to react samples directly in an NMR tube and subsequently monitor the reaction by HSQC-NMR avoids the usual lignin derivatization and purification problems that can lead to some loss of sample; we were ready to apply the method to isolated lignins.…”

Section: Resultsmentioning

confidence: 99%

Method to Regioselectively Iodine-Tag Free-Phenolic Aromatic End-Groups in Lignin for¹H–¹³C-HSQC NMR Analysis

Ando

Ralph

2019

ACS Sustainable Chem. Eng.

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Phenolic end-groups on lignin molecules are important sites for continued lignification, their influence over lignin molecular properties, their ability to enhance lignin degradation, and their potential for derivatization to produce lignin materials. Here we use iodination to regioselectively tag, and HSQC-NMR to monitor, guaiacyl phenolic aromatic end-groups in lignins. Using dimeric lignin models, iodination at the 5-position of the phenolic ring was shown to be clean, and almost quantitative. Additionally, the 6-position C/H correlation peak shifted downfield in both carbon and proton dimensions in HSQC spectra. As phenolic aromatic rings could be selectively iodinated, and as their C6/H6 aromatic signals appear in a clear region of HSQC NMR spectra (different from the original position), we would have a new method for tagging and analyzing such phenolic aromatic rings in lignins if the method could be applied to the polymer. The new tagging method was therefore applied to a synthetic guaiacyl lignin polymer (DHP) and a milled wood lignin (MWL) isolated from Japanese cedar (Cryptomeria japonica). The derivatization proceeded directly in the NMR tube, without needing isolation or purification, from which HSQC-NMR revealed that the diagnostic C6/H6 correlations matched one from the dimeric model compound. This phenolic unit tagging method adds a useful method to the lignin structural analysis toolbox, helping to gain a better understanding of lignin's phenolic end-units.

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“…Iodination of aromatic compounds has been carried out using molecular iodine together with strong oxidising agents such as nitric acid, sulphuric acid, iodic acid, sulphur trioxide and hydrogen peroxide, 3 ceric ammonium nitrate, 4 bismuth(III) nitrate pentahydrate, 5 sodium hypochlorite and urea-hydrogen peroxide. 6 Several reagents reported for iodination of aromatic compounds include iodine and 1,4-bis(triphenylphosphonium)-2-butene peroxodisulfate, 7 iodine and pyridine/ dioxane, 8 AgNO 3 /I 2 , 9 I 2 /NaBO 3 $4H 2 O in ionic liquid, 10 I 2 /HIO 3 , heat, 11 I 2 /CrO 3 , 13 NaClO 2 /NaI/HCl, 14 KI/K 2 FeO 4 in water, 15 N-iodosuccinimide and catalytic triuoroacetic acid, 16 pyCl/ CH 3 OH, 17 I 2 /Pb(OAc) 4 , 12 KI/H 2 O 2 , 18 KI/KIO 3 /H + , 19 KClO 3 /KI/ HCl, 20 NCS/NaI 21 and iodine with H 2 O 2 and O 2 . 22 Strong Lewis acids or Bronsted acids, such as triuoroacetic acid, 23 tri-uoromethanesulfonic acid and BF 3 $OEt 2 -H 2 O 24 have been utilised for electron-withdrawing groups on the aromatic ring, which is not suitable for acid-sensitive functional groups.…”

Section: Introductionmentioning

confidence: 99%

Recyclable ionic liquid iodinating reagent for solvent free, regioselective iodination of activated aromatic and heteroaromatic amines

et al. 2015

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This article describes a simple, efficient method for iodination of activated aromatic and heteroaromatic amines using recyclable 1butyl-3-methylpyridinium dichloroiodate (BMPDCI) as an ionic liquid iodinating reagent, in the absence of any solvent. The main advantages are simple efficient procedure, good yields and no need of any base/toxic heavy metals, or oxidizing agent. The ionic liquid was recovered and recycled in five subsequent reactions, without much loss of activity. This method was applied for the synthesis of antiprotozoal drug Iodoquinol and antifungal drug Clioquinol.

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Convenient and Efficient Method for the Iodination of Aromatic Amines by Pyridinium Iodochloride

Cited by 11 publications

References 21 publications

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Method to Regioselectively Iodine-Tag Free-Phenolic Aromatic End-Groups in Lignin for¹H–¹³C-HSQC NMR Analysis

Recyclable ionic liquid iodinating reagent for solvent free, regioselective iodination of activated aromatic and heteroaromatic amines

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Convenient and Efficient Method for the Iodination of Aromatic Amines by Pyridinium Iodochloride

Cited by 11 publications

References 21 publications

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Method to Regioselectively Iodine-Tag Free-Phenolic Aromatic End-Groups in Lignin for1H–13C-HSQC NMR Analysis

Recyclable ionic liquid iodinating reagent for solvent free, regioselective iodination of activated aromatic and heteroaromatic amines

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Method to Regioselectively Iodine-Tag Free-Phenolic Aromatic End-Groups in Lignin for¹H–¹³C-HSQC NMR Analysis