8-Methoxy-5-methyl-2,3-dihydro-1<Emphasis Type="Italic">H</Emphasis>-cyclopenta[<Emphasis Type="Italic">a</Emphasis>]naphthalene: synthesis and reactivity

A new single-step approach to cyclopenta[a]naphthalenes through TiCl₄-catalyzed reactions of 1-trimethylsilyloxycyclopentene with arylacetaldehydes was proposed. 8-Methoxy-5-methyl-2,3-dihydro-1H-cyclopenta[a]naphthalene and its derivatives were studied in oxidation and bromination reactions, as well as in hydrolytic cleavage of the O-Me bond.     

An efficient synthesis of 1-cyanoacetyl-5-halomethyl-4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazoles in ionic liquid

The synthesis of eleven 1-cyanoacetyl-5-hydroxy-5-halomethyl-4,5-dihydro-1H-pyrazoles from the reaction of 4-alkoxy-3-alken-2-ones f(R ³C(O)C(R ²) = C(R ¹)OR, where R ³ = CF₃, CCl₃, CHCl₂, CO₂ Et; R ²/R ¹ = H/H, H/Me, H/Et, -(CH₂)₄-, Me/H, H/Pr, and R = Me, Et) with cyanoacetohydrazide is reported. The reaction was carried out in the ionic liquid ([bmim][BF₄]) and molecular solvents. The results showed that when the ionic liquid was used as reaction medium, the reaction time was drastically decreased and the yield was improved. Correspondence: Marcos A. P. Martins, Núcleo de Química de Heterociclos – NUQUIMHE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil.     

Regioselective synthesis of polyfluoroalkyl-substituted 7-(1<Emphasis Type="Italic">H</Emphasis>-1,2,3-triazol-1-yl)-6,7-dihydro-1<Emphasis Type="Italic">H</Emphasis>-indazol-4(5<Emphasis Type="Italic">H</Emphasis>)-ones

3-Polyfluoroalkyl-6,6-dimethyl-7-(1H-1,2,3-triazol-1-yl)-6,7-dihydro-1H-indazol-4(5H)-ones were synthesized with high regioselectivity by 1,3-dipolar cycloaddition of terminal alkynes (phenylacetylene, hex- 1-yne, hept-1-yne, and but-3-yn-1-ol) to 7-azido-6,6-dimethyl-3-polyfluoroalkyl-6,7-dihydro-1H-indazol-4(5H)-ones which were prepared by bromination of 6,6-dimethyl-3-polyfluoroalkyl-6,7-dihydro-1H-indazol- 4(5H)-ones with N-bromosuccinimide in anhydrous carbon tetrachloride, followed by treatment of the corresponding 7-bromo derivatives with sodium azide.     

Synthesis and properties of 1,2-dihydro-4(3<Emphasis Type="Italic">H</Emphasis>)-quinazolinones

We modified the preparative-scale method for the synthesis of 2-aryl 1,2-dihydro-4(3H)-quinazolinone derivatives obtained in high yields by the reaction of new and commercially available aromatic aldehydes with anthranilic acid amides. A series of quinazolinone derivatives possessing anticancer and antiparasitic activities, as well as capable of preventing the progress of neurodegenerative diseases were characterized. There are grounds for clinical trials of these substances in order to select compounds being promising for clinical application.     

Electrophilically activated nitroalkanes in the synthesis of 6,7-dihydro-1<Emphasis Type="Italic">H</Emphasis>-cyclopenta[<Emphasis Type="Italic">g</Emphasis>]perimidines

A highly efficient synthetic route to 6,7-dihydro-1H-cyclopenta[gh]perimidines has been proposed on the basis of a novel reaction of nitroalkanes with 4,5-diaminoacenaphthene in the presence of polyphosphoric acid. The reaction involves phosphorylation of the aci-nitro compound, followed by intramolecular cyclization.     

<Emphasis Type="Italic">S</Emphasis>-functional derivatives of 3,4-dihydro-2<Emphasis Type="Italic">H</Emphasis>-1,4-thiasilines

The first cyclic unsaturated S-functional derivatives of 4,4-diphenyl-3,4-dihydro-2H-1,4-thiasiline, S-oxide, S,S-dioxide, and S-sulfonimide, were prepared. Oxidation of the hydrolytically less stable 4,4-dimethyl-3,4-dihydro-2H-1,4-thiasiline leads to the corresponding sulfoxide and sulfone along with the ring opening products, siloxanes containing the sulfoxide or sulfonyl group.     

Tautomerism of azacycles: III. Molecular and crystal structures of 3<Emphasis Type="Italic">H</Emphasis>-and 2-phenyl-1<Emphasis Type="Italic">H</Emphasis>,4<Emphasis Type="Italic">H</Emphasis>-4,5-dihydro-1,2,4-triazole-5-thiones

Compounds capable of tautomerism: sulfanyl-1,2,4-triazole, its C-phenyl derivative, and the crystal hydrate of the latter, were studied by single crystal X-ray diffraction. In the crystals they exist in the form of 3-R-1(H),4(H)-4,5-dihydro-1,2,4-triazole-5-thione with a considerable contribution of the bipolar structure. Published data on the tautomerism of sulfanyl-1,2,4-triazoles and their N-substituted analogs and on the correlation between the spectral characteristics and structures of sulfanyl-1,2,4-triazoles capable of tautomerism are discussed.     

Reaction 5-(Arylmethylidene)pyrimidine-2,4,6(1<Emphasis Type="Italic">H</Emphasis>,3<Emphasis Type="Italic">H</Emphasis>,5<Emphasis Type="Italic">H</Emphasis>)-triones with L-Proline and Aldehydes

Boiling in toluene of 5-(arylmethylidene)pyrimidine-2,4,6(1H,3H,5H)-triones with L-proline and aldehyde led to the formation of previously unknown substituted 1′-arylhexahydro-1H-spiro[pyrimidine-5,2′-pyrrolysine]-2,4,6(1H,3Н,5Н)-triones.     

Regioselectivity in the reactions of <Emphasis Type="Italic">N</Emphasis>-(polychloroethylidene)-sulfonamides with 1<Emphasis Type="Italic">H</Emphasis>-pyrrole and 1-methyl-1<Emphasis Type="Italic">H</Emphasis>-pyrrole

N-(2,2,2-Trichloroethylidene)arenesulfonamides react with 1H-pyrrole and 1-methyl-1H-pyrrole to give the corresponding N-[2,2,2-trichloro-1-(1H-pyrrol-2-yl)ethyl]arenesulfonamides. The reaction of N-(2,2,2-trichloroethylidene)trifluoromethanesulfonamide with pyrrole leads to a mixture of 2-mono-and 2,5-disubstituted pyrroles, whereas in the reaction with 1-methyl-1H-pyrrole only the 2-substituted compound is formed. N-(2,2-Dichloro-2-phenylethylidene)-4-methylbenzenesulfonamide reacts with 1H-pyrrole to form N-[2,2-dichloro-2-phenyl-1-(1H-pyrrol-2-yl)ethyl]-4-methylbenzenesulfonamide, and its reaction with 1-methyl-1H-pyrrole gives a mixture of 2-and 3-monosubstituted derivatives. The results of quantum-chemical calculations of the initial reactants and products indicate that the process is orbital-controlled. A good agreement is observed between the experimental data and theoretical conclusions concerning the dependence of the reaction regioselectivity on the nature of substituents in the electrophile molecule.     

Synthesis of carbamate derivatives of 2,3-dihydro-4<Emphasis Type="Italic">H</Emphasis>-1,4-benzoxazine

Alkylation of methyl 2-hydroxyphenylcarbamates with 1,2-dibromoethane in acetone in the presence of K₂CO₃ gave the corresponding methyl 6(7)-R-2,3-dihydro-4H-1,4-benzoxazine-4-carboxylate. Alkylation of methyl 2-hydroxyphenylcarbamates with chloromethyloxirane was accompanied by recyclization of the oxirane ring with formation of methyl 6(7)-R-3-hydroxymethyl-2,3-dihydro-4H-1,4-benzoxazine-4-carboxylates.     

Synthesis of isoxazole derivatives of 4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazole

Cyclocondensation of pent-1-en-4-yn-3-one with phenylhydrazine and p-tolylhydrazine occurs at the positions 1, 3. Proceeding from the 1-aryl-3-ethynyl-4,5-dihydro-1H-pyrazoles formed in the reaction in yields up to 95% we prepared potentially biologically active isoxazole derivatives of pyrazoline. The structure of 5-[1-(4-methylphenyl)-4,5-dihydro-1H-pyrazol-3-yl]-3-phenyl-1,2-oxazole was studied by X-ray diffraction analysis.     

One step synthesis of 14-alkyl- or aryl-14<Emphasis Type="Italic">H</Emphasis>-dibenzo[<Emphasis Type="Italic">a</Emphasis>,<Emphasis Type="Italic">j</Emphasis>]xanthenes using sodium hydrogen sulfate as catalyst

A simple and environmentally benign procedure for the synthesis of 14-alkyl- or aryl-14H-dibenzo[a,j]xanthenes is described through a one-pot condensation of 2-naphthol with aryl or alkyl aldehydes in the presence of sodium hydrogen sulfate as a catalyst under solvent-free conditions. Correspondence: Mohammed M. Hashemi, Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran.     

Recyclization of 1,3-dialkyl-6-nitro-1<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridine-2,5(3<Emphasis Type="Italic">H</Emphasis>,4<Emphasis Type="Italic">H</Emphasis>)-diones into imidazole derivatives

Treatment of 5-amino-1,3-dialkyl-2,3-dihydro-1H-imidazo[4,5-b]pyridin-2-ones with sodium nitrite in aqueous HCl gave 1,3-dialkyl-1H-imidazo[4,5-b]pyridine-2,5(3H,4H)-diones which were nitrated with potassium nitrate in sulfuric acid to 6-nitro derivatives, and the latter underwent recyclization into 4-amino-1,3-dialkyl-5-(1H-pyrazol-5-yl)-2,3-dihydro-1H-imidazol-2-ones by the action of hydrazine hydrate.     

Nitration of 3-methyl-6,7-dihydro-1<Emphasis Type="Italic">H</Emphasis>-indeno[6,7,1-<Emphasis Type="Italic">def</Emphasis>]cinnoline and its <Emphasis Type="Italic">N</Emphasis>-substituted derivatives

The nitration of 3-methylaceperidazine (3-methyl-6,7-dihydro-1H-indeno[6,7,1-def]cinnoline) and its N-substituted derivatives with nitric acid of different concentrations requires harsh conditions and is accompanied by dehydrogenation and dimerization of the initial compound.     

Reaction of acetylenedicarboxylic acids esters with 4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazole-1-carbothioamides and 3,4,5,6-tetrahydro-2<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazepine-3-thiones

The reactions of dimethyl acetylenecarboxylate with 3,4,5,6-tetrahydro-2H-1,2,4-triazepine-3-thiones and 4,5-dihydro-1H-pyrazole-1-carbothioamides are convenient methods for the synthesis of 7,8-dihydrothiazolo[3,2-b][1,2,4]triazepin-3-ones derivatives and methyl esters of (2Z)-[2-(4,5-dihydro-1H-pyrazol-1-yl)-4-oxo-1,3-thiazol-5(4H)-ylidene]acetic acids, respectively. The reaction of methyl propynoates with 4,5-dihydro-1H-pyrazole-1-carbothioamides or with 5,5,7-trimethyl-2,4,5,6-tetrahydro-3H-1,2,4-triazepine-3-thione gives 2-(4,5-dihydro-1H-pyrazol-1-yl)-4H-1,3-thiazin-4-ones.     

Reactions of 3-Aroylpyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]quinoxaline-1,2,4(5<Emphasis Type="Italic">H</Emphasis>)-triones with 2,3-Dihydrofuran and 3,4-Dihydro-2<Emphasis Type="Italic">H</Emphasis>-pyran

3-Aroylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones reacted with 2,3-dihydrofuran and 3,4-dihydro-2H-pyran to give mixtures of the corresponding hetero-Diels–Alder (furo- and pyrano[3″,2″: 5′,6′]pyrano- [4′,3′: 2,3]pyrrolo[1,2-a]quinoxalines) and Michael adducts (furyl- and pyranylpyrrolo[1,2-a]quinoxalines).     

Straightforward and solvent-free synthesis of 2-amino-4<Emphasis Type="Italic">H</Emphasis>-chromenes in the presence of a choline-based magnetic ionic liquid as catalyst

Choline tetrachloroferrate with a magnetic response property is applied in multicomponent one-pot synthesis of 2-amino-4H-chromenes as effective catalyst. The catalyst is characterized by the UV–Vis and Raman spectroscopies and by the electrospray ionization mass spectrometry.     

Ultrasound-Assisted Synthesis of 5<Emphasis Type="Italic">H</Emphasis>-Chromeno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine Derivatives

An environmentally friendly method has been developed for the preparation of 5H-chromeno[2,3-b]pyridine derivatives in an aqueous medium under ultrasound irradiation.