Reaction of 4-chloropyrimidines with alkylisothioureas

4,6-Dichloro-5-nitropyrmidine reacts with S-methylisothiouronium sulfate to give 1-(4-chloro-5-nitropyrimidin-6-yl)-S-methylisothiourea by an unusual nucleophilic attack involving an isothiouronium nitrogen atom.     

An electrochemical synthesis of functionalized arylpyrimidines from 4-amino-6-chloropyrimidines and aryl halides

A range of novel 4-amino-6-arylpyrimidines has been prepared under mild conditions by an electrochemical reductive cross-coupling between 4-amino-6-chloro-pyrimidines and functionalized aryl halides. The process, which employs a sacrificial iron anode in conjunction with a nickel(II) catalyst, allows the formation of coupling products in moderate to high yields.     

Palladium-catalyzed amidation of 2-chloropyrimidines

A mild and efficient Pd-catalyzed coupling of amides with 2-chloropyrimidines is described. The use of bidentate phosphines, such as Xantphos (7), as supporting ligands was found to be crucial for providing high yields of 2-(N-acylamino)pyrimidine coupling products 1.     

Pyrimidones. 2. Synthesis and reactions of 2-chloropyrimidines

The treatment of 1-alkyl-5-aryl and 1-alkyl-4,5-diaryl-2-(1H)pyrimidones with phosphorus oxychloride and phosphorus pentachloride resulted in chlorination and dealkylation to furnish 2-chloro-5-aryl (or 4,5-diaryl)-pyrimidines. These chlorpyrimidines were reacted with a variety of nitrogen, oxygen, sulfur, and carbon nucleophiles to produce the corresponding 2-substituted pyrimidines. In the case of phenyllithium, attack occurred at the 4-position of the pyrimidine ring yielding 11 . Triazolopyrimidine 9 was synthesized via the treatment of 2d with hydrazine followed by reaction with triethyl orthoformate.     

Synthesis of 2- and 4-chloropyrimidines with hydroxyphenyl substituents by the interaction of Vilsmeier-Haack reagents with (hydroxyphenyl)dihydropyrimidin-2- and -4-ones

The reaction of 2- and 4-hydroxypyrimidines containingortho- andpara-hydroxyphenyl substituents with Vilsmeier-Haack reagents generatedin situ from DMF and SOCl₂ or POCl₃ results in the chemoselective replacement of the heterocyclic hydroxyl group by chlorine and formylation of the phenolic hydroxyl group. Aryl formates are hydrolyzed under the conditions of their isolation to give the corresponding phenols, especially if the pyrimidyl fragment isortho to the formyloxy group.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1993.     

3-Quinuclidinol as a nucleophilic catalyst for the cyanation of 2-chloropyrimidines

3-Quinuclidinol serves as an effective nucleophilic catalyst for the preparation of 2-cyanopyrimidines by cyanation of 2-chloropyrimidines with potassium cyanide in good yields.     

Synthesis and Antimicrobial Activity of Novel Azolopyrimidines and Pyrido‐Triazolo‐Pyrimidinones Incorporating Pyrazole Moiety

A new series of azolopyrimidine derivatives incorporating pyrazole moiety were synthesized by reaction of 1‐(pyrazol‐3‐yl)‐2‐propenone with a number of heterocyclic amines in the presence of a catalytic amount of acetic acid. The mechanism of formation of the products was also discussed, and the structure assigned was elucidated based on both elemental and spectral analyses data. In addition, 7‐(pyrazolyl)‐2‐thioxo‐5‐phenyl‐1,3‐dihydropyrido[2,3‐d ]pyrimidin‐4‐one was used as starting material for preparation of a new series of pyridotriazolopyrimidines via its reaction with a variety of hydrazonoyl chlorides in dioxane using triethylamines as catalyst. The assigned structure for these products was also proved via elemental analysis and spectroscopic techniques (IR, ¹H NMR, and Mass). Moreover, the antimicrobial activity of some selected examples of the new products was evaluated, and the results obtained revealed high activity of compound 20a against the Gram positive bacteria Staphylococcus aureus and the Gram negative bacteria Klebsiella pneumonie . All the tested compounds have no antifungal activity.     

4-Isoxazolines and pyrroles from allenoates

The synthesis of 4-isoxazolines via 1,3-dipolar cycloaddition of nitrones generated from allenoates and the subsequent thermal rearrangement to pyrroles is reported. The selection of the reaction conditions allowed the isolation of the initial 1,3-dipolar cycloadducts, the 4-isoxazolines, or the pyrrole derivatives. The isomerization of the parent system (4-isoxazoline) was examined by carrying out quantum chemical calculations and corroborated the favourability of the 4-isoxazoline rearrangement to five-membered heterocycles via 2-acylaziridine intermediates.     

X-ray diffraction study on liquid crystals from 4-hexylphenyl 4-cyanobenzoyloxybenzoate and 4-heptyloxyphenyl 4-cyanobenzoyloxybenzoate

X-ray investigations were performed on 4-hexylphenyl 4-cyanobenzoyloxybenzoate (DB6CN) and on 4-heptyloxyphenyl 4-cyanobenzoyloxybenzoate (DB7OCN). For both compounds, the smectic A₂ structure is observed. From the small angle meridional reflections, the angular distribution of the smectic units around the normal to the smectic layers and the longitudinal correlation length were studied. The orientational order parameter is calculated from the wide angle equatorial reflections. Based on the assumption of a layer structure with undulation in the liquid crystalline smectic A phase, the relationship between the dimensionless parameters χch/dL (correlation length/thickness of the smectic layer) and FWHM/2θ₀ (full width at the half maximum/maximum point of the scattering peak) is simulated.     

Synthesis of 4-aminopolymethoxycoumarins from 4-hydroxycoumarin triflates

4-Aminocoumarins were synthesized in high yields by the reaction of 4-hydroxycoumarin trifluoromethanesulfonates with amines. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1583–1588, September, 2006.     

C-alkyl-4-nitropyrazoles from 5-chloro-4-nitropyrazoles

5-Chloro-4-nitro-1H-pyrazoles reacted with arylsulfonyl-, cyano-, and acetylacetic acid esters in DMSO in the presence of potassium carbonate to give 5-[alkoxycarbonyl(acetyl, cyano, or arylsulfonyl)-methyl]-substituted 4-nitropyrazoles which may be promising from the viewpoint of preparation of other functionalized pyrazole derivatives and bicyclic ensembles.     

4-Aminouracils and pyrimido[4,5-b]indolediones from 4-azidouracils

Azidouracils (3), which are obtained from barbituric acids (1), can easily be cyclized to pyrimido[4,5-b]indoles (4) or converted into 4-aminouracils (6).Dedicated to Prof. Dr.E. Ziegler on the occasion of his 75th birthday.     

Merocyanine dyes from 4-dicyanomethylene-2,6-dimethyl-4H-pyran

Neutral dyes were prepared by reacting 1-ethyl-2[2-(N-methylanilino)vinyl]quinolinium iodide with 4-dicyanomethylene-2,6-dimethyl-4H-pyran and then condensing the resulting product with an aromatic aldehyde.     

A NMR identification of isomeric Meisenheimer adducts from 4-nitrobenzofurazan and 4-nitrobenzofuroxan

It has been shown by NMR spectroscopy that both 4-nitrobenzofurazan and 4-nitrobenzofuroxan give isomeric σ-adducts, which result from methoxide addition at the non-substituted 5-and 7-carbons.     

Green approach for the synthesis of 4-coumarin-4H-pyrans from 4-formylcoumarins and their antibacterial study

A series of 4H-pyranocoumarin derivatives have been successfully synthesized under eco-friendly condition using triethylamine as a catalyst in short reaction time with excellent yield at room temperature. All the synthesized compounds were characterized by spectral analysis and screened for their antibacterial activity against Escherichia coli and Staphylococcus aureus, the results are quite promising.