A highly efficient multicomponent synthesis of pyridones and pyrimidones by a [2+2+2] strategy

Fluorinated enol ethers: their synthesis and reactivity

This review sums up the methods for the preparation of fluorinated enol ethers as well as their numerous synthetic applications.

Synthesis of 4-chalcogeno-1-aza-1,3-butadiene derivatives by intramolecular cyano-Diels-Alder reaction and borane-coordination-induced fluorescence enhancement

4-Thio-1-aza-1,3-butadiene derivatives 3 incorporating a rigid dibenzobarrelene skeleton were synthesized by the intramolecular cyano-Diels-Alder reaction of 9-anthryl cyanoethenyl sulfides 6. The thermal reaction of 6 afforded an equilibrium mixture of 3 and 6, but the cyclization was effectively promoted by the addition of BF3·Et2O or B(C6F5)3 to yield imine-borane adducts 8 and 9. The imine-borane adducts emit intense blue fluorescence both in solution and in the crystalline state. This is in stark contrast to free imines 3, which are weakly fluorescent. Selenium analogue 4 and N-oxide 12 of 3a were synthesized, along with their B(C6F5)3 adducts.

Synthesis and luminescent properties and theoretical investigation on electronic structure of nitrile-based 2-pyridone molecules

3-Cyano-4,6-dimethyl-2-pyridone and 3-cyano-4-methyl-6-phenyl-2-pyridone were synthesized effectively by the reaction of readily available 1,3-diketone and malononitrile directly and in good yield. Upon photoexcitation, 3-cyano-4-methyl-6-phenyl-2-pyridone in ethanol shows strong blue emission. The ground- and excited-state geometries, charge distributions, and excitation energies of 2-pyridone derivatives were evaluated by ab initio calculations. Organic light-emitting diodes (OLED) made using 3-cyano-4-methyl-6-phenyl-2-pyridone as dopant showed blue light emission with a maximum electroluminescence (EL) emission at around 456 nm.

The synthesis of highly functionalised pyridines using Ghosez-type reactions of dihydropyrazoles

The aza-Diels-Alder reaction of αβ-unsaturated hydrazones is a general methodology that has been applied both to the synthesis of natural products and in the development of multicomponent reactions. Trends have emerged as to the effect of substituents on the efficiency of this reaction with substituents at the C2 and C4-positions of the aza-diene in general suppressing the reaction. Here we report that 4,5-dihydropyrazoles can function as substrates in this process despite the presence of substituents at both of these positions. A one pot, four chemical step sequence carried out under standard thermal or microwave conditions results in the formation of the corresponding pyridine-containing compounds. The scope of the reaction is explored and additional insights into the proposed mechanism of this reaction are provided.

Synthesis of pyrimidines by direct condensation of amides and nitriles

A protocol for the single-step synthesis of pyrimidine derivatives by condensation of N-vinyl or N-aryl amides with nitriles is described. Gram-scale synthesis of 4-tert-butyl-2-phenyl-7,8-dihydro-6H-pyrano[3,2-d]pyrimidine serves as a representative procedure for this methodology for azaheterocycle synthesis. This chemistry involves amide activation with trifluoromethanesulfonic anhydride in the presence of 2-chloropyridine and the necessary nitrile. Nucleophilic addition of the nitrile to an activated intermediate followed by annulation affords the pyrimidine product in a single step. The total time necessary for the completion of this procedure is approximately 3 h. This chemistry has been applied to a wide range of amides and nitriles including optically active derivatives.