New synthesis of 2(1H)-pyridone derivatives

The reaction of N¹-acyl-2-ethoxycarbonylacetamidrazones 1 with diethyl ethoxymethylenemalonate (EMME) is reported. By refluxing equimolecular amounts of 1 and EMME in DMSO/toluene (or ethanol) solution, the 1-acylamino-2(1H)-pyridones 2 were obtained in good yield. When the reaction was performed in ethanolic solution in the presence of triethylamine, the 6-acylhydrazino-2(1H)-pyridones 3 were obtained.     

Proton-coupled 13C NMR and {14N}—1H-INDOR of highly-substituted 6-membered heterocycles. I—trisubstituted pyridones and isomeric aminopyrones; tetrasubstituted pyridines

The structural elucidation by NMR spectroscopy of trisubstituted α-pyridones and the isomeric 2-amino-γ-pyrones as well as their internal and external pyrylium salts is described. The most useful parameter for the differentiation between α-pyridones and isomeric γ-pyrones is the geminal coupling constant ²J(C-6, H-5) which changes from ～2.5 Hz to ～7 Hz whenever the cyclic amide group is replaced by an oxa-function; this applies to both the γ-pyrones and their pyrylium salts. The value of J(C-6, H-5) in the pyridones resembles that of the analogous coupling in N-vinylacetamide, whose sign determination by the selective population inversion (SPI) technique is reported. The ¹³C chemical shifts of seven pyridones, pyrones and pyrylium salts are reported and their structural correlations are discussed. Quick structural assignments in these classes of compounds may also be performed by evaluating the ¹⁴N chemical shifts, which often are accessible by the {¹⁴N}—¹H-INDOR technique. The proton coupled ¹³C NMR spectra of two tetrasubstituted pyridines are also reported, and empirical correlations between long range C? H coupling constants and substituent electronegativity are discussed.     

Synthesis and evaluation of dihydroimidazolo and dihydrooxazolo ring-fused 2-pyridones—targeting pilus biogenesis in uropathogenic bacteria

Dihydrothiazolo ring-fused 2-pyridones have previously been shown to inhibit pilus assembly in uropathogenic Escherichia coli. Methods have now been developed to synthesize both dihydroimidazolo and dihydrooxazolo ring-fused 2-pyridones. To obtain the nitrogen analogs, Cbz-protected imidazolines were reacted with an acyl-Meldrum's acid derivative under acidic conditions. To prepare the oxygen analogs, a one-pot procedure was developed that allowed synthesis of dihydrooxazolo ring-fused 2-pyridones starting from acylated serine derivatives. After hydrolysis to their corresponding carboxylic acids and lithium carboxylates, biological evaluation revealed that the sulfur could be replaced by an oxygen atom and still maintains the ability to inhibit pilus assembly in uropathogenic E. coli. However, introducing a secondary amine instead of oxygen resulted in a substantial decrease in biological activity.     

Ring transformations of 4H-pyrans. Pyridines from 2-amino-4H-pyrans

Ring transformations of 4H-pyrans into pyridines are reported. Treatment of 2-amino-4,6-diaryl-3,5-dicyano-4H-pyrans (I) with nitrosylsulfuric acid brings about their transformation into 3,5-dicyano-4,6-diaryl-2-pyridones (VI) which can also be obtained from α-benzoylcinnamonitriles (IX) and cyanoacetamide. Similarly, 2-amino-4,6-diaryl-5-carbethoxy-3-cyano-4H-pyrans (II) lead to 4,6-diaryl-5-carbethoxy-3-cyano-2-pyridones (VII). Treatment of both series of pyrans with sulfuric acid results in the formation of the corresponding 3,4-dihydro-2-pyridones (IV and V). Reaction of pyrans II with ammonium acetate in acetic acid yields 2-amino-4,6-diaryl-5-carbethoxy-3-cyanopyridines (XII). Pyrans I undergo an entirely different type of reaction upon treatment with this reagent leading to 2,4,6-triaryl-3,5-dicyano-1,4-dihydropyridines (XV).     

Preparation and reactions of 3,4-dihydro-2H-pyran-2-ones

The Michael reaction of ethyl cinnamates with deoxybenzoin gave ethyl 3,4,5-triaryl-5-oxopentanoates which were hydrolysed to the corresponding acids. The latter could be cyclized to the respective 3,4-dihydro-2H-pyran-2-ones which underwent ring opening with several nucleophiles to the corresponding acid derivatives. However, their reaction with ammonium acetate led to the formation of 3,4-dihydro-2-pyridones. The 3,4-dihydro-2-pyrones and pyridones were dehydrogenated to the corresponding 2-pyrones and 2-pyridones by fusion with sulfur.     

Tetracyanoalkanones in the synthesis of heterocycles. Synthesis of 3,4-dicyano-2(1H)-pyridones by the interaction of tetracyanoalkanones with pyruvic acid

Tetracyanoalkanones react with pyruvic acid with the formation of 3,4-dicyano-5,6-dialkyl-2(1H)-pyridones, the structure of which was confirmed by IR, ¹³C NMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1225–1228, September, 1985.     

Ultra-long Near-infrared Repeatable Photochemical Afterglow Mediated by Reversible Storage of Singlet Oxygen for Information Encryption

Photochemical afterglow systems have drawn considerable attention in recent years due to their regulable photophysical properties and charming application potential. However, conventional photochemical afterglow suffered from its unrepeatability due to the consumption of energy cache units as afterglow photons are emitted. Here we report a novel strategy to realize repeatable photochemical afterglow (RPA) through the reversible storage of ¹O₂ by 2-pyridones. Near-infrared afterglow with a lifetime over 10 s is achieved, and its initial intensity shows no significant reduction over 50 excitation cycles. A detailed mechanism study was conducted and confirmed the RPA is realized through the singlet oxygen-sensitized fluorescence emission. Furthermore, the generality of this strategy is demonstrated and tunable afterglow lifetimes and colors are achieved by rational design. The developed RPA is further applied for attacker-misleading information encryption, presenting a repeatable-readout.     

Reactions of 5-(het)aryl-1-ethyl-2(1<Emphasis Type="Italic">H</Emphasis> )-pyrazinones with terminal arylacetylenes promoted by microwave radiation

The reaction of 5-(het)aryl-1-ethyl-2(1H)-pyrazinones with terminal arylacetylenes, leading to a mixture of two isomeric 4-aryl- and 5-aryl-substituted 2(1H)-pyridones has been investigated. The regioselectivity of this reaction has been shown on the basis of reaction mixtures study by chromato-mass spectrometry. A crystallographic investigation of the synthesized 2(1H)-pyridones and also a forecast of their potential biological activity have been carried out.     

Heterocycles. Part V. Reaction of α,β-unsaturated carbonyl compounds with arylacetamides. A synthesis of 2-pyridone derivatives

The reaction of 1,3-diaryl-2-propene-1-ones I with arylacetamides II, in the presence of sodium ethoxide under reflux, for two hours, gave the corresponding 3,4,6-triaryl-3,4-dihydro-2(1H)-pyridones IV. However, when the reaction of these ketones was carried out in the presence of sodium hydride, they gave the corresponding 3,4,6-triaryl-2(1H)-pyridones VI or a mixture of IV and VI. When 1,3-diaryl-2-propyne-1-ones V were reacted with arylacetamides, in the presence of sodium hydride, they yielded the corresponding 2-pyridones VI. Treatment of compounds IV with selenium produced the corresponding 2-pyridones VI. Acetylation of the latter compounds gave the corresponding 2-acetyl derivatives VIII. The structure of all products was confirmed by chemical and spectroscopic evidence, and the mechanism of the reactions was discussed.     

Pyridinethiones. VIII. The aldol and wittig condensations of 3-formyl-2(1H)-pyridones, -thiones and -selones. Preparation of new cyanopyridones

Condensations of 1-substituted-3-formyl-2(1H)-pyridones, -thiones and -selones with methyl ketones such as acetophenone give the corresponding chalcones in high yields. Geometry at the vinyl hydrogens is E. These chalcones can be cyclized with ethyl cyanoacetate in the presence of ammonium acetate to form new 3-cyano-2(1H)-pyridones. An effective “one-pot” preparation is worked out and an intermediate from the cyclization reaction is isolated. Via the Wittig reaction it is possible to prepare condensation products from 1-substituted-3-formyl-2(1H)-pyridinethiones and -selones with mainly Z geometry at the vinyl hydrogens.     

Retro-ene reactions in heterocyclic synthesis. II. A facile synthetic method for 4-hydroxy-2-pyridones

Schiff's bases 1 derived from ketones and t-butylamine reacted with diphenyl malonate, diphenyl methyl-malonate and diphenyl phenylmalonate to give 4-hydroxy-2-pyridones 4–6 . Schiff's bases b on reaction with trimethyl methanetricarboxylate afforded 4-hydroxy-3-methoxycarbonyl-2-pyridones 12 .     

Multinuclear NMR (1H,13C,15N,17O) studies of intramolecular interactions in 1-vinylpyridones and quinolones

¹H and¹³C NMR was used to estimate the dihedral angles between the planes of the vinyl group and the hetero ring for 1-vinylpyridones and quinolones. The¹H,¹³C,¹⁵N, and¹⁷O NMR data showed the existence of a specific intramolecular weak hydrogen bond between the -H atom of the vinyl group and the O atom in 1-vinyl-2-pyridones and 2-vinyl-1-isoquinolone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1539–1547, July, 1990.     

Enantiomers of sterically hindered n-aryl-4-pyridones: Chromatographic enrichment and thermal interconversion

N-Aryl-4-pyridones 1–6 were synthesized by condensation of the corresponding 4-pyrone with anilines. The enrichment of the enantiomers was achieved by liquid chromatography on triacctylcellulose, enantiomeric purities of(+)-1 and (+ )-2 being measured by ¹H-NMR in the presence of an optically active auxiliary. Barriers to partial rotation about the C-N bond in 1-4 were determined and compared with corresponding biphenyls.     

Electron-impact induced fragmentation of 2-substituted pyridines and picolines

The fragmentation patterns obtained upon electron impact on 2-nitro-, 2-chloro, and 2-aminopyridines, as well as those of the corresponding 3-, 4-, 5- and 6-picolines were examined. There was considerable departure from those patterns reported for the corresponding benzenoid derivatives. Although the molecular ion from 2-nitro-3-picoline did not show fragment ions attributable to an “ortho-effect” (unlike o-nitrotoluene), those from 2-chloro- and 2-amino-3-picolines did show a loss of HCl and NH₃, respectively. Quite unexpectedly the ions from 2-chloro- and 2-amino-6-picolines also lost HCl and NH₃. Such meta-eliminations for the 2-substituted-6-picolines are postulated to be preceeded by either hydrogen or methyl migration. The mass spectra of 2-pyridone, 2-pyridthione and their respective 3-, 4-, 5- and 6-methyl analogs were also studied. The primary fragmentations of the 2-pyridones were as expected from those reported in the literature. The ions from 3- and 6-methyl-2-pyridones lost water also, the former being another example of an “ortho-effect” observed in this series. Of the thiones, the fragmentations of 3-methyl-2-pyridthione proved most unique since its molecular ion showed besides the loss of HS, the pronounced elimination of H₂S, the latter presumably due to an “ortho-effect.” Figures are presented to illustrate the patterns and metastable ions are indicated when found for the transitions discussed.     

A comparative screening of the catalytic activity of nanocrystalline M<Superscript>II</Superscript>Zr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript> ceramics in the one-pot synthesis of 1,6-diamino-4-aryl-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile derivatives

A four-component reaction of hydrazine hydrate, ethyl cyanoacetate, malononitrile, and aromatic aldehydes was achieved in the presence of nanocrystalline M^IIZr₄(PO₄)₆ ceramics (M^II: Mn, Fe, Co, Ni, Cu, Zn, Cd) as heterogeneous catalysts to produce N-amino-2-pyridones. The reactions were performed in the presence of different catalysts, and it is observed that CdZr₄(PO₄)₆ nanocrystallines are the best catalysts among those examined. Atom economy, excellent yields in short times, high catalytic activity, recycling of catalyst, and environmental benignity are some of the important features of this protocol.     

Synthesis and properties of 1-(6-methoxy)-2-benzothiazolyl)-2-pyridones

Substituted ]-(6-methoxy-2-benzothiazolyt)-2-pyridones were prepared from 2-amino-6-methoxybenzathiazate through N-(6-methoxy-2-benzothiazotyl) cyanvorearmileaznd-3-aryl-N-(6-methoxy-2-benzothiazolyt)-2-cyano-2-propenamides. The cyclization of the latter with malonodinitrile in the presence of piperidine gave the corresponding pyridones. The structures of the synthesized compounds were confirmed by¹H NMR and mass spectral data.Department of Organic Chemistry, Mass Spectrometry Laboratory, Slovak Technical University, 812 37 Bratislava, Slovakia. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1402–1404, October, 1995. Original article submitted August 24, 1995.     

Reactions of ketene silyl acetals with imine-complexes of titanium tetrachloride. New and convenient routes to 5,6-dihydro-2-pyridones and 5-amino-2-alkenoates

The reactions of vinylketene silyl acetals (VKSAs) with imine complexes of TiCl₄ give the corresponding 5,6-dihydro-2-pyridones and/or 5-amino-2-alkenoates in good to excellent yields. It is suggested that an addition-cyclization mechanism is operative for the formation of 5,6-dihydro-2-pyridones in this formal cyclocondensation reaction.     

The diels-alder chemistry of 1-vinyl-2-pyridones

The Diels-Alder chemistry of a series of 1-vinyl-2-pyridones using a variety of dienophilic species including dimethyl acetylenedicarboxylate, benzyne, maleic anhydride and methyl vinyl ketone has been explored in order to determine the generality of this method for generation of N-vinylisoquinuclidines. In general, the cycloaddition reactions lead to modestly high yeilds of the azabicyclooctane products. In the course of these studies, we noted that retro-Diels-Alder reactions of N-vinylisoquinuclidienones lead to generation of N-vinylisocyanates and a benzene fragment while the corresponding mono-unsaturated isoquinuclidenones form the corresponding pyridones by elimination of an ethylene unit. Lastly, the regio- and stereochemical courses for the π2+ π4 addition reactions of methyl vinyl ketone and 1-vinyl-2-pyridones were investigated. The major products from these reactions appear to result from reaction pathways predicted to be of low energy using first-order molecular orbital methods.     

A novel stereocontrolled synthesis of enantiopure bicyclic lactams

A study on the reactivity of 3,4-dihydro-2-pyridones 9, derived from (S)-phenylglycinol, toward different bases is presented. Using a catalytic amount of bases, the cis bicyclic lactams were obtained with excellent diastereoselectivities.