A facile and efficient method for the synthesis of novel pyridone analogues by aminolysis of an ester under solvent-free conditions

A series of 15 pure novel N-alkylated pyridone derivatives have been synthesized in 73-96% yields on treatment of ethyl (2-pyridone)acetates with structurally diverse amines in an efficient aminolysis procedure under ‘solvent-free’ conditions.     

Transition-metal-free highly efficient synthesis of 2-pyridones from β-keto amides and ynals

A convenient and efficient annulation reaction was developed, affording 2-pyridones in good to excellent yields. A variety of substituted β-keto amides and ynals were well tolerated, and especially the transformation produced water as only by-product under transition-metal-free conditions. Furthermore, the conjugated enyneamides were achieved from β-cyano amides and ynals in high yields.     

Reversible Redox System of 2-Oxypyritriphyrin(1.2.1) Accompanying Interconversion between 3-Pyridone and 3-Hydroxypyridine Units

To develop a system in which a π-conjugation circuit switched by a redox reaction between 3-pyridone and 3-hydroxypyridine, a ring-contracted analog of oxypyriporphyrin, 2-oxypyritriphyrin(1.2.1) was synthesized for the first time. 2-Oxypyritriphyrin(1.2.1) contains a 14π aromatic conjugation circuit with the keto-form of the 3-oxypyridine ring. When 2-oxypyritriphyrin was treated with NaBH₄, not only the 3-oxypyridine group, but also the meso-carbons were also reduced to give a colorless porphyrinogen analog. The reduced compound could be oxidized again to provide 2-oxypyritripyhrin in a reversible manner.     

Synthesis and reactivity of 3-amino-1H-pyrazolo[4,3-c]pyridin-4(5H)-ones: development of a novel kinase-focussed library

3-Amino-1H-pyrazolo[4,3-c]pyridin-4(5H)-ones represent a potentially attractive heteroaromatic scaffold for drug-discovery chemistry. In particular, the arrangement of hydrogen bond donor and acceptor groups in the bicyclic core can fulfil the requirements for ATP competitive binding to kinase enzymes. Efficient and regioselective routes from simple starting materials to novel functionalised 3-amino-1H-pyrazolo[4,3-c]pyridin-4(5H)-ones and related 3-amino-2H-pyrazolo[4,3-c]pyridines were explored and adapted for parallel synthesis, resulting in a library of compounds suitable for screening against kinases and other cancer drug targets. Methods for substituent variation at five distinct positions around the bicyclic core were devised to generate sets of compounds containing two- or three-point diversity.     

Construction of C-nucleosides diversified by [3+2] cycloaddition from a sugar-based mesoionic ring

A mesoionic acyclic C-nucleoside (4), serves as the starting chiron to construct highly functionalized 2-aza-7-thiabicyclo[2.2.1]heptanes and heptenes by means of a [3+2] cycloaddition with acetylenic and olefinic dipolarophiles. Further elimination of either sulfur or hydrogen sulfide leads to acyclic C-nucleosides bearing a heterocyclic moiety of 2-pyridone.     

An annulation method for the synthesis of alkyl-substituted 6-carbomethoxy-2-pyridones

A protocol for the synthesis of 5-alkyl and 3,5-dialkyl-6-carbomethoxy-2-pyridones was devised. Key steps include a Mannich reaction, acylation of a tosylamine, and a PPh₃/TiCl₄-promoted intramolecular Reformatsky-type reaction with a thioester as the electrophile. The latter process typically afforded a vinylogous thiocarbamate via elimination of water rather than the Dieckmann-type product which would have resulted from elimination of the thiol. However, the Dieckmann-type ketone product was obtained in one instance. Subsequent elimination of the tosyl group and desulfurization completed the pyridone synthesis.     

A facile synthesis of 5,6-dihydro-5-hydroxy-2(1H)-pyridone

A short synthesis of 5,6-dihydro-5-hydroxy-2(1H)-pyridone was achieved from l-serine employing Horner-Emmons olefination as the key step.     

Synthesis,spectroscopic properties and applications of novel N-heterocycle-containing benzotriazoles as UV absorbers

Two novel iV-heterocycle-containing benzotriazole compounds,5-(5-chloro-2-benzotriazolyl)-6-hydroxy-l,4-dimethyl-3-car-bonitrile -2-pyridone(2) and 4-(5-chloro-2-benzotriazoIyl)-5-methyl-2-phenyl-3-pyrazolone(4),were synthesized from reactant 4- chloro-2-nitroaniline via diazotization,azo coupling,reductive cyclization and acidification.Their structures were confirmed by FT-IR,~1H NMR,mass spectroscopy and elemental analysis.Their spectral properties were investigated and compared with that of a common commercial benzotriazole UV absorber Tinuvin 326.It is found that the novel Af-heterocycle-containing benzotriazole compounds exhibit sharp single peak in the range of 280-400 nm and have much higher molar extinction coefficients than that of Tinuvin 326.Their anti-UV protection properties on polyester fabric were also evaluated and compound 4 was much superior to compound 2 due to its higher exhaustion.