Photocatalyst-Free Singlet Oxygen-Induced Oxygenation: A Strategy for the Preparation of 5-Cyano-2-pyridones Driven by Blue-Light Irradiation

Bi(III)-Catalyzed Michael Addition of Tautomerizable Heterocycles with α,β-Unsaturated Carbonyl Compounds: Regioselective Construction of C-N Bonds

A Bi(III)-catalyzed synthetic strategy for regioselective construction of C-N bonds via a simple Michael addition reaction is reported. A wide range of tautomerizable heterocycles such as benzoxazolones, benzothiazolones, benzimidazolinones, indolinones, and 2-pyridones along with α,β-unsaturated carbonyls (ketones and esters) are employed to create a library of corresponding N-alkylated derivatives exclusively. High regioselectivity, high atom economy, and the participation of a range of tautomerizable heterocycles highlight the uniqueness and generality of the developed methodology.

Access to 2-pyridinones comprising enaminonitriles via AgOAc promoted cascade reactions of thioesters with aminomethylene malononitriles

The facile synthesis of 2-pyridinones containing enaminonitriles from thioesters with aminomethylene malononitriles is achieved through an AgOAc-promoted acylation/cyclization/tautomerization cascade reaction. Control experiments reveal that AgOAc acts as a versatile promoter, activating both thioester and cyano groups while also serving as a Brønsted base in the cascade sequence. Moreover, 2-pyridinones were transformed into biologically significant 2-pyridinone-fused 2-pyrimidones with intriguing fluorescence emission properties.

Crystal structure of 9-(t-butyl)-3,11-dihydro-6H-pyrazolo [1,5-a]pyrrolo[3′,2′:5,6]pyrido[4,3-d]pyrimidin-6-one hemihydrate, C30H32N10O3

C30H32N10O3, monoclinic, P21/c (no. 14), a = 10.447(2) Å, b = 20.130(4) Å, c = 14.772(3) Å, β = 113.001(3)°, V = 2859.7(10) Å3, Z = 4, R gt (F) = 0.0556, wR ref (F 2) = 0.1663, T = 296 K.

Fe(III)-Catalyzed Tandem Cyclization of Phenylpropiolamides with 3-Formylchromones for the Construction of 2-Pyridones

A highly efficient and atom-economic iron(III)-catalyzed three-component heteroannulation reaction between phenylpropiolamides, 3-formylchromones, and water is described for the construction of diversely multifunctionalized 2-pyridones. This protocol allows rapid access to a variety of 2-pyridones bearing an ortho-hydroxybenzoyl and a benzoyl scaffold under operationally simple conditions. The synthetic utility of the synthesized 2-pyridone scaffolds is demonstrated by transformation into biologically interesting complex heterocycles.

Construction of 3,12-Diazatetracyclododecane-dienes through Unexpected Visible-Light-Induced Radical Cascade Cyclization

A novel visible-light-induced cascade radical cyclization reaction of 3-cyano-4-aryl-1,4-dihydropyridines for the construction of 3,12-diazatetracyclododecane-diene derivatives is reported for the first time. In the presence of 410 nm blue LED lamp as the light source and ethanol as the solvent, the reactions proceed smoothly to afford photocyclization products in good yields. The process is carried out through the breaking of original C═C double bonds and the formation of three new single bonds in one pot and proved to be able to tolerate different substituents.

Crystal structure of 1-(2-cyanobenzyl)-3-cyano-4-phenyl-4-(2-cyanobenzyl)-1,4-dihydropyridine monohydrate, C56H42N8O

C56H42N8O, orthorhombic, Pbcn (no. 60), a = 17.885(3) Å, b = 15.647(2) Å, c = 16.189(2) Å, V = 4530.4(11) Å3, Z = 4, R gt (F) = 0.0464, wR ref (F 2) = 0.1219, T = 296.15 K.

Visible-Light-Induced Photocatalyst-Free Aerobic Hydroxyazidations of Indoles: A Highly Regioselective and Stereoselective Synthesis of trans-2-Azidoindolin-3-ols

A visible-light-promoted aerobic hydroxyazidation of indole derivatives with TMSN₃ is described. The reaction proceeded under photocatalyst-free conditions to furnish trans-2-azidoindolin-3-ols with high regioselectivity and stereoselectivity. The protocol is operationally simple, and the starting materials (e.g., 1-(pyrimidin-2-yl) indoles, azidotrimethylsilane, and air) are readily available. The proposed mechanism in which substrates act as photocatalysts upon excitation using blue light-emitting diodes (LEDs) was supported by experimental studies.

Photosensitizer-free synthesis of β-keto sulfones via visible-light-induced oxysulfonylation of alkenes with sulfonic acids

A practical and environment-friendly methodology for the construction of β-keto sulfones through visible-light induced direct oxysulfonylation of alkenes with sulfonic acids at ambient temperature under open-air conditions was developed. Most importantly, the reaction proceeded smoothly without the addition of any photocatalyst or strong oxidant, ultimately minimizing the production of chemical waste.

Photooxidation of 2-(tert-Butyl)-3-Methyl-2,3,5,6,7,8-Hexahydroquinazolin-4(1H)-one, an Example of Singlet Oxygen ene Reaction

Singlet oxygen ene reactions produce 2-(tert-butyl)-4a-hydroperoxy-3-methyl-2,4a, 5,6,7,8-hexahydroquinazolin-4(3H)-one quantitatively during diffusion crystallization of 2-(tert-butyl)-3-methyl-2,3,5,6,7,8-hexahydroquinazolin-4(1H)-one in n-hexane/CH₂Cl₂ solvent mixture. To confirm this photo-oxidation, a ¹H-NMR study in CDCl₃ was performed with exposure to ambient conditions (light and oxygen), with neither additional reactants nor catalysts. A theoretical study at the B3LyP/6311++G** level using the QST2 method of locating transition states suggests a two-step mechanism where the intermediate, which unexpectedly did not come from the peroxide intermediate, has a low activation energy.