Halogenation of enol tautomers of 2-cyanoacetamide and malonamic acid

Eberlin, Alex R.; Williams, D. Lyn H.

doi:10.1039/b202542f

Cited by 8 publications

(4 citation statements)

References 17 publications

(12 reference statements)

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“…This is due to the feasibility for hydrogen-bond stabilization in the two former compounds which is lacking in the cyanoacetamide. Williams' experimental values in water are higher, being 9.1 (malonamide) and 9.22 (cyanoacetamide) 13b…”

Section: Resultsmentioning

confidence: 84%

Enols of Substituted Cyanomalonamides

et al. 2007

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Twenty open-chain mono-, di-, and trialkyl and aryl-N-substituted cyanomalonamides R2R1NCOCH(CN)CONHR3 were prepared. In solution, signals for both amide and a single enol are mostly observed, despite the potential for E and Z isomeric enols. The equilibrium (KEnol) values between the amides and the enols were determined in different solvents by NMR spectra. They decrease on increasing the polarity of the solvent in the order CDCl3 approximately C6D6>THF-d8>(CD3)2CO>CD3CN>DMF-d7>DMSO-d6. For the R1R2NCOCH(CN)CONHR3 system when R1=R2=H, Me or R1=H, R2=Me, KEnol for R3 follows the order: C6F5>Ph>or=An>or= i-Pr>or= t-Bu, and for R1, R2:H, H>Me, H>Me, Me in all solvents. A unique feature is the appreciable % enol in DMSO-d6 when R1=R2=H, in contrast with enol systems with other electron-withdrawing groups (EWGs). Calculations (B3LYP/6-31G**) corroborate the higher KEnol values for less alkyl-substituted systems, showing that in the most stable conformer when R1=H, R2=R3=Me the N-hydrogens are closer to the CN group. The order of promoting substituents for enol of amide formation is CONH2>CO2CH2CF3>CO2Me>CONHMe. The solid-state structures of the isolated species, determined by X-ray crystallography, were either amides or enols, and a higher KEnol(CDCl3) value does not ensure a solid enol structure. In no system were both solid species isolated. The X-ray structures of the enols were temperature-dependent. In most cases, the difference between the O-H and O...H bond lengths at low temperature were appreciable, but they become closer at the higher temperature. Similar tendency for either the C=C/C-C or the C-O/C=O bonds was observed. This is ascribed to a hydrogen shift between two regioisomeric enols in an asymmetric double-well potential, which becomes faster at a higher temperature. Calculations show that the enol structures are nonsymmetrical, resembling the lower temperature structures, even when they are chemically symmetrical, but the energy differences between the two regioisomers are <1 kcal. The hydrogen bonds in the enol moiety are strong, with O...O distances <2.45 A, and are resonance-assisted hydrogen bonds. IR spectra in solution and the solid state qualitatively corroborate the NMR and X-ray structure determination.

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Section: Resultsmentioning

confidence: 84%

Enols of Substituted Cyanomalonamides

et al. 2007

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“…A comparative study of the brominating capability of the aqueous AlBr3-Br2 system with the recently circulated methods is testified in Table 2 which clearly indicates the benefits of the present system over obtainable methods. In this present study, we are presenting, a effective reagent system for electron-withdrawing groups (EWG) like; -COOH, NO2 and -CHO as examples of pharmaceutical reaction intermediates under purely aqueous conditions (Eberlin et al, 2002;Edwards et al, 2009;Fong et al, 2009).…”

Section: Stirringmentioning

confidence: 99%

A direct and simplistic bromination of commercially important organic compounds in aqueous media by eco-friendly AlBr3-Br2 reagent system

Sharma¹,

Agarwal²

2019

Preprint

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A facile, simplistic, highly efficient, environmentally safe, regioselective, controllable and economical method for the bromination of organic compounds using aqueous AlBr3-Br2 reagent system was investigated. As synthesized brominated organic compounds were characterize using advanced techniques. The yield was all synthesized brominated organic compounds was excellent with high purity. Results revealed that this direct and simple bromination of commercially important organic compounds in aqueous media in the presence of recycle of AlBr3-Br2 reagent system is efficient method and could possibly be extended for the synthesis of other organic compounds.

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“…The solvents used for the abstraction of products were removed under abridged pressure (where-ever required) using Buchirotavapour. The spectra were logged in CDCl3, MeOD and DMSO as solvents unless otherwise noted (Eberlin et al, 2002;Firouzabadi et al, 2003). Chemical shifts are described in parts/million relative to tetramethylsilane as an internal standard, for 1 H and 13 C NMR spectra.…”

Section: Reagents and Analyticsmentioning

confidence: 99%

Synthesis of cetylpyridiniumtribromide (CetPyTB) reagent by noble synthetic route and bromination of organic compounds

Int¹

2019

Preprint

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Cetylpyridiniumtribromide (CetPyTB) was prepared by a noble synthetic protocol and reactivity studies was also performed. Result indicates that the reagent shows good capability as a brominating agent for carbon/electron-rich heterocyclic aromatic compounds in addition to an efficient catalyst for acetylation of the alcohols, therefore proving it to be a note-worthy addition to the current organic tribromide reagents.

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Halogenation of enol tautomers of 2-cyanoacetamide and malonamic acid

Cited by 8 publications

References 17 publications

Enols of Substituted Cyanomalonamides

Enols of Substituted Cyanomalonamides

A direct and simplistic bromination of commercially important organic compounds in aqueous media by eco-friendly AlBr3-Br2 reagent system

Synthesis of cetylpyridiniumtribromide (CetPyTB) reagent by noble synthetic route and bromination of organic compounds

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