2 pyridone tautomerism pdf

A mild cucatalyzed approach for the narylation of 2 pyridones with diaryliodonium salts proceeds readily at room temperature to provide narylpyridine 2 ones in very good yields. The reaction 2 pyridone py e 2 hydroxypyridine hp has been studied as a prototype of tautomerism of heteroaromatic compounds. The aromatic resonance energy of 2pyridone and the related thione, methide, and imine. Transition from water wires to bifurcated hbond networks in 2 pyridone h2on, n 14 clusters.

Tautomerism is the phenomenon of chemical isomers structures that have the same atomic composition, e. It represents an important class of compounds, which have. The arylazo pyridone dyes prepared in this study may exist in two tautomeric forms fig. Some substituted 2 pyridones form the dimer in solid state, for example the 5methyl3carbonitrile 2 pyridone. The high phosphatetransfer potential of phosphoenolpyruvate results from the fact that the phosphorylated compound is trapped in the less thermodynamically favorable enol form, whereas after dephosphorylation it can assume the keto form. It is distinct from prototropic tautomerism, and involves processes with rapid reorganisation of bonding electrons.

Introduction, history, and recent developments the estimated rise in log k e is only log k e. The infrared spectra of all the synthesized dyes table ii showed 436 mijin et al. Under the same expansion condition, the fluorescence signal of the tautomeric form of the complex 2 hydroxypyridineformic acid is absent, although both the bare tautomeric molecules. This video illustrates several cases, including the title case. Systematically characterizing the tautomer exchange rates as a function of various experimental variables lead to a twostate concerted mechanism involving bridging water wires for the lactamlactim tautomerization of 6chloro 2 pyridone. A series of some novel arylazo pyridone dyes was synthesized from the corresponding diazonium salt and 6hydroxy4phenyl3cyano2pyridone using a classical reaction for the synthesis of the azo compounds.

Note that in all the examples of ketoenol tautomerism the two isomeric forms are interconvertible by v tautomerism. As illustrated for the 4isomer l, these ketones differ from their nonheterocyclic analogues in forming an enamine 2 or, in the case of the 3isomer, a zwitterionic 3 as well as enol 4 tautomers. Tautomerism and microsolvation in 2hydroxypyridine2. The interconversion of the two forms involves the movement of an alpha hydrogen atom and the reorganisation of bonding electrons. Together with pyridones, the tautomerism of pyrazolones has been studied most intensely and serves as a model for other work on. Matrixisolation ftir study on the protomeric tautomerism 2. Giao ab initio calculations of absolute shieldings have been carried out to identify the predominant tautomers in the case of compounds pdf version of thesis. Pdf tautomerization of formamide, 2pyridone, and 4. Kinetics of singlet oxygen release from endoperoxides of 2. Tautomerism of 1hydroxy 2 pyridone and 1hydroxypyridine 2 thione in the excited triplet state. Transition from water wires to bifurcated hbond networks in 2pyridoneh2on, n 14 clusters. Experimental and quantum chemical study ismail ajaja, fathi h.

Both the title compounds show dual phosphorescence depending on the excitation wavelength and the nature of the solvents at 77k. Pyridone dyes with alkyl and aryl groups in ortho position to azo group show 2pyridone2hydroxypyridine tautomerism, while those contg. Phenyl6hydroxy3cyano2pyridone was prepared from ethyl benzoylacetate and cyanoacetamide using a modified literature procedure 14. Tautomerization of formamide, 2pyridone, and 4pyridone. The tautomerism between 2 hydroxypyridine and 2 pyridone has been con. As illustrated for the 4isomer l, these ketones differ from their nonheterocyclic analogues in forming an enamine 2 or, in the case of the 3. This coupling reaction is mild, highyielding, remarkably chemoselective n vs. The neutral 2hydroxypyridine2pyridone tautomerism was widely studied 11,12. The keto and enol forms are said to be tautomers of each other. The work is compared with other estimates of the aromaticity of these compounds.

Synthesis and antimicrobial activity of some 2pyridone nucleosides containing a sulfonamide moiety. The tautomerism of 2 pyridone, 6chloro 2 pyridone, and 4pyrimidinone have been examined in d 2 o using ftir, twodimensional ir 2d ir spectroscopy and density functional theory dft calculations. The tautomerism between 2hydroxypyridine and 2pyridone has been con. Reaction of cobaltii salts and the anion of 6chloro2pyridone results in the formation of a trinuclear structure which has been characterised by xray. The explanation must lie in the conjugation present in 2 pyridone 4a itself, which, while less than the aromaticity of its iminol 4b,is. Only the 2pyridone tautomerism has been observed directly in the gas phase, and theory is in good agreement with all three experimental values 0.

Pdf reinvestigation of the tautomerism of some substituted 2. The molecules 4hydroxypyridine 1 and 4pyridone 2sch. This was also confirmed by thermodynamic calculations and isodesmic reactions. The vibrational spectrum of 2hydroxypyridine isolated in an ar matrix was studied using ftir spectroscopy.

A series of some novel arylazo pyridone dyes was synthesized from the corresponding diazonium salt and 6hydroxy4phenyl3cyano 2 pyridone using a classical reaction for the synthesis of the azo compounds. Tautomerism and microsolvation in 2hydroxypyridine2pyridone. Ionization behaviour and tautomerismdependent lipophilicity. H values obtained are used to demonstrate that 2pyridone and 2pyridinethione retain most of the aromatic resonance energy of pyridine, that 2pyridone imine is also strongly aromatic, but that 2pyridone methide is far less so. Cuicatalyzed coupling reactions of tetrabutylammonium pyridin2olates with aryl iodides allow an efficient synthesis of naryl pyridine2ones. These data have been discussed in relation with the tautomerism of the four heterocycles. The reaction 2pyridone py e 2hydroxypyridine hp has been studied as a prototype of tautomerism of heteroaromatic compounds. The thermodynamic and kinetic properties of 2hydroxypyridine2. Synthesis of substituted ringfused 2pyridones and applications in chemical biology abstract antibiotics have been extensively used to treat bacterial infections since alexander flemings discovery of penicillin 1928. Tautomerization of formamide, 2 pyridone, and 4 pyridone. In the solid state the dimeric form is not present. Solvatochromism and azohydrazo tautomerism of novel arylazo pyridone dyes.

It tautomerizes to form 2 pyridone 2 py by a proton transfer between the nitrogen and oxygen atoms 1. Luca siffert, susan blaser, philipp ottiger, samuel leutwyler. The geometrical structures, dipole moments, homolumo energy gaps, total hyperpolarizability, kinetics and. It tautomerizes to form 2pyridone 2py by a proton transfer between the nitrogen and oxygen atoms. Disease causing microbes that have become resistant to. Synthesis, structure and solvatochromic properties of 53 and 4substituted phenylazo4,6diphenyl3cyano2.

Synthesis of substituted ring fused 2pyridones and. This group of alkaloids has a pyridone nucleus and generally takes the tetracyclic or tricyclic form. Nh3 as a strong hbond donor in singly and doublybridged ammonia solvent clusters. Matrixisolation ftir study on the protomeric tautomerism. The explanation must lie in the conjugation present in 2pyridone 4a itself, which, while less than the aromaticity of its iminol 4b,is. Figure 2 shows the tautomer selection dialog box currently highlighting 6hydroxyquinolin21hone, which is predicted correctly as being the major form by the algorithm, in agreement with the spectral analyses. Nmr spectroscopic data do not allow discrimination between the two tautomeric forms with the exception of the unsubstituted 2hydroxypyridine. The tautomerism of 2pyridone, 6chloro2pyridone, and 4pyrimidinone have been examined in d2o using ftir, twodimensional ir 2d ir spectroscopy and density functional theory dft calculations. Original article solvatochromism and azohydrazo tautomerism of novel arylazo pyridone dyes. Some substituted 2pyridones form the dimer in solid state, for example the 5methyl3carbonitrile2pyridone. In organic chemistry, ketoenol tautomerism refers to a chemical equilibrium between a keto form a ketone or an aldehyde and an enol an alcohol.

Transition from water wires to bifurcated hbond networks in. Some substituted 2 pyridones form the dimer in solid state, for example the 5methyl3carbonitrile 2pyridone. Geometrical structures and relative energies of the two tautomers as welt as of the transition state ts for the. Ketoenol and imineenamine tautomerism of 2, 3 and 4. Tautomerism of sixmembered heterocyclic compounds 125 fig. All structured data from the file and property namespaces is available under the creative commons cc0 license.

Several c and 15 n chemical shifts of 2pyridone 1, 43 h pyrimidone 2, uracil 3 and cytosine 4 have been measured in solution and in the solid state. Tautomerism in computeraided drug design pavel pospisil, patrick ballmer, leonardo scapozza, and gerd folkers. Ketoenol tautomerism in acetoacetic ester is proved by the fact that under ordinary conditions the compound gives the properties of the ketonic group as well as that of the enolic group. Oarylation, and tolerates labile functional groups. Current interest focuses on proton transfer from 2pyridone and its tautomer, using isotope. Pyridone dyes with alkyl and aryl groups in ortho position to azo group show 2 pyridone 2 hydroxypyridine tautomerism, while those contg. Files are available under licenses specified on their description page. Several c and 15 n chemical shifts of 2 pyridone 1, 43hpyrimidone 2, uracil 3 and cytosine 4 have been measured in solution and in the solid state. Pdf azohydrazone tautomerism of aryl azo pyridone dyes. The equilibrium between the 2pyridone form i and 2hydroxypyridine form ii of the 53 and 4substituted phenyl. Figure 2 shows the tautomer selection dialog box currently highlighting 6hydroxyquinolin 2 1hone, which is predicted correctly as being the major form by the algorithm, in agreement with the spectral analyses.

This method was then applied to study the tautomerism of a deoxycytidine analog, kp1212, which is an antihiv drug. The most common type of tautomerism is that involving carbonyl, or keto, compounds and unsaturated hydroxyl compounds, or enols. The thermodynamic and kinetic properties of 2hydroxypyridine. Synthesis, properties and colour assessment of some new 5.

It tautomerizes to form 2pyridone 2py by a proton transfer between the nitrogen and oxygen atoms 1. Synthesis of nheterocycles synthesis of 2 pyridones. Tautomerism, the existence of two or more chemical compounds that are capable of facile interconversion, in many cases merely exchanging a hydrogen atom between two other atoms, to either of which it forms a covalent bond. Only the 2 pyridone tautomerism has been observed directly in the gas phase, and theory is in good agreement with all three experimental values 0. Two specific further subcategories of tautomerizations. Synthesis, structure and solvatochromic properties of some. These data have been discussed in relation with the tautomerism of the four hete. Results and discussion spectral characteristics and tautomerism the arylazo pyridone dyes prepared in this work may exist in two main tautomeric forms. Synthesis, structure and solvatochromic properties of 53. Ketoenol tautomerism is important in several areas of biochemistry. Oct 06, 2010 this article is cited by 23 publications.

Twodimensional infrared spectroscopy of nucleic acids. Studies on novel pyridine and 2pyridone derivatives of narylpiperazine as. The neutral 2hydroxypyridine 2pyridone tautomerism was widely studied 11,12. Tautomerism is often an important step in heterocyclic reactions. Research article open access synthesis, structure and. Under the same expansion condition, the fluorescence signal of the tautomeric form of the complex 2hydroxypyridineformic acid is absent, although both the bare tautomeric molecules. Tautomerism in computeraided drug design pavel pospisil, patrick ballmer, leonardo scapozza, and gerd folkers department of chemistry and applied biosciences, swiss federal institute of technology eth zu. Tautomerism of 1hydroxy2pyridone and 1hydroxypyridine. The coordination chemistry of 2pyridone and its derivatives. On the tautomerization reaction 2pyridone2hydroxypyridine.

Unlike other classes of isomers, tautomeric compounds exist in mobile. Annular tautomerism is a type of prototropic tautomerism wherein a proton can occupy two or more positions of a heterocyclic system, for example, 1h and 3himidazole. It is well known to form hydrogen bonded dimers and it is also a classic case of a compound that exists as tautomers. Feb 11, 2010 tautomerism is often an important step in heterocyclic reactions.