Zinc-Mediated Cyclodimerization of 1,5-Diaryl-1,4-pentadien-3-one in Aqueous Solution Under Ultrasound Irradiation

Synthesis of 2-cinnamoyl-1-styryl-3,4-diarylcyclopentanol via cyclodimerization of 1,5-diaryl-1,4-pentadien-3-one mediated by zinc was carried out in good yields at room temperature in NH₄Cl (aq.) and tetrahydrofuran under ultrasonic irradiation. In comparison with conventional methods, the main advantages of the present procedure are shorter reaction time and better yields.     

A novel TMSI-mediated synthesis of Hantzsch 1,4-dihydropyridines at ambient temperature

The synthesis of various substituted Hantzsch 1,4-dihydropyridines has been achieved using the classical Hantzsch procedure and modified Hantzsch conditions for the first time at room temperature in the presence of iodotrimethylsilane (TMSI) generated in situ in CH₃CN, in excellent yields.     

The mass spectral fragmentation of some 2,3-dihydro-5-trifluoromethyl-7-(p-R-phenyl)-1,4-diazepines

Summary Electron impact mass spectra of seven 2,3-dihydro-5-trifluoromethyl/methyl-7-(p-R-phenyl)-1,4-diazepinesR=H, CH₃, OCH₃, CF₃, Cl, Br) have been recorded and are discussed. These systems dissociate by scission of the C₂-C₃ bond followed by loss of H^. to give the [M-H]⁺ ion as the base peak. The fragmentation behaviour has been investigated using metastable scanning techniques and accurate mass measurements. The origin of some characteristic fragment ions is discussed.

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Massenspektroskopische Fragmentierung einiger 2,3-Dihydro-5-trifluormethyl-7-(p-R-phenyl)-1,4-diazepine

Zusammenfassung Die EI-Massenspektren von 7 2,3-Dihydro-5-trifluormethyl/methyl-7-(p-R-phenyl)-1,4-diazepinen (R=CH₃, OCH₃, CF₃, Cl, Br) werden vorgestellt. Diese Verbindungen fragmentieren unter Spaltung der C₂-C₃-Bindung. Anschließende Abspaltung von H^. führt zum Fragment [M-H]⁺, das als Basispeak auftritt. Das Fragmentierungsverhalten wurde mittels metastabiler Methoden und genauer Massenbestimmungen untersucht. Die Herkunft einiger charakteristischer Fragmentionen wird diskutiert.

     

Synthesis of novel unsymmetrical coumarinyl-1,4-dihydropyridines

The novel unsymmetrical 3,5-dialkoxycarbonyl-2,6-dimethyl-4-(7′,8′-dimethoxycoumarin-4′-yl)-1,4-dihydropyridines and 5-acetyl-3-alkoxycarbonyl-2,6-dimethyl-4-(7′,8′-dimethoxycoumarin-4′-yl)-1,4-dihydropyridines (coumarinyl-1,4-dihydropyridines) have been synthesized by Knoevenagel condensation of 4-formyl-7,8-dimethoxycoumarin with alkyl acetoacetates in the presence of AlCl₃ followed by cyclization of the resulted Knoevenagel product with other alkyl acetoacetate or acetyl acetone and ammonium acetate. The structure of the intermediate Knoevenagel product and the cyclized unsymmetrical coumarinyl-1,4-dihydropyridines has been established on the basis of their spectral data analysis and single-crystal X-ray diffraction analysis. The observed conformation of the coumarinyl-1,4-dihydropyridines holds the key to promising calcium antagonistic activity of the synthesized coumarinyl-1,4-dihydropyridines.     

Catalytic aromatization of Hantzsch 1,4-dihydropyridines by ferric perchlorate in acetic acid

Catalytic oxidation of Hantzsch 1,4-dihydropyridines is described using a catalytic amount of ferric perchlorate in acetic acid at room temperature.     

Simons electrochemical fluorination of substituted homopiperazines(hexahydro-1,4-diazepines) and piperazines

Simons electrochemical fluorination (ECF) of 1,4-dimethyl-1,4-homopiperazine, methyl 4-ethylhomopiperazin-1-ylacetate and 1,4-bis(methoxycarbonylmethyl)-1,4-homopiperazine was studied. For comparison, ECF of three piperazines with a N-(methoxycarbonylmethyl) group(s) was also studied. ECF of 1,4-dimethyl-1,4-homopiperazine gave a low yield of corresponding perfluoro(1,4-dimethyl-1,4-homopiperazine) together with perfluoro(2,6-diaza-2,6-dimethylheptane) as the major product. Corresponding perfluoro(homopiperazines) with mono- and/or di-(fluorocarbonyldifluoromethyl) groups [CF₂C(O)F] at the 1- and/or 4-position were formed in low yields from methyl 4-ethylhomopiperazin-1-ylacetate and 1,4-bis(methoxycarbonylmethyl)-1,4-homopiperazine, respectively. These new seven-membered perfluoro(1,4-dialkyl-1,4-homopiperazines) were accompanied by the formation of mono- and/or di-basic linear perfluoroacid fluorides resulting from the CC bond scission at the 2- and 3-positions of the ring. From mono- and/or di-N-(methoxycarbonylmethyl)-substituted piperazines, corresponding perfluoropeperazines having the acid fluoride group(s) were formed in low yields.     

PREPARATION AND CHARACTERIZATION OF cis-,4-POLYBUTADIENE CONTAINING A FRACTION OF trans-1,4-POLYBUTADIENE

Polymerization of butadiene catalysed first with V(acac)_3-Al(i-Bu)_2Cl, then with Co(acac)_3-H_2O-Al(i-Bu)_2Cl has been studied. The polymer obtained was identified to be a new variety of cis-1,4-polybutadiene which contained a fraction of trans-1,4-polybutadiene chemically bonded to the cis-1,4-polybutadiene chains. Its molecular weight and trans-1,4 content can be regulated by varying the catalyst composition and concentration as well as other polymerization conditions. The trans-1,4 fraction, although it presents only in 9—16%, forms a crystalline phase in the matrix at room temperature and facilitates the crystallization of the polymer.     

Efficient and Convenient Synthesis of 1,4-Benzoxazines, 1,4-Benzothiazines,Spiro-1,4-benzoxazines,and Spiro-1,4-benzothiazines

An efficient, convenient synthesis of 1,4-benzoxazines, 1,4-benzothiazines, spiro-1,4-benzoxazines, and spiro-1,4-benzothiazines derivatives was accomplished in good yields via the novel intramolecular cyclization mediated by mild base K₂CO₃ in ethanol solvent. A variety of substrates can participate in the process with good yields, making this methodology have broad applicability. All the structures of synthesized compound have been confirmed by spectral analysis.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® to view the free supplemental file.     

Synthesis and calcium channel antagonist activity of new symmetrical and asymmetrical 4-[2-chloro-2-(4-chloro-6-methyl-2-oxo-2H-pyran-3-yl)vinyl]-substituted 1,4-dihydropyridines

New symmetrical 4-[2-chloro-2-(4-chloro-6-methyl-2-oxo-2H-pyran-3-yl)vinyl]-substituted 1,4-di-hydropyridines were synthesized in moderate to good yields via the modified Hantzsch reaction of β-dicarbonyl compounds with (Z)-3-chloro-3-(4-chloro-6-methyl-2-oxo-2H-pyran-3-yl)acrolein in the presence of an excess amount of NH₄OAc. Also, the reaction of β-dicarbonyl compounds with (Z)-3-chloro-3-(4-chloro-6-methyl-2-oxo-2H-pyran-3-yl)acrolein in the presence of enamino esters and ketones was performed, and asymmetrical 4-[2-chloro-2-(4-chloro-6-methyl-2-oxo-2H-pyran-3-yl)vinyl]-substituted 1,4-dihydropyridines were obtained in moderate to good yields at room temperature. The calcium channel blocking activity of these compounds was assessed. They demonstrated moderate to weak effects, although one compound had a comparable effect (IC₅₀ =1.40×10⁻⁷ M) with respect to the reference drug Nifedipine.     

An efficient aerobic oxidative aromatization of Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazolines

4-Substituted Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazolines were oxidized to the corresponding pyridines and pyrazoles, respectively, in high yields by molecular oxygen in the presence of catalytic amount of N-hydroxyphthalimide (NHPI) and Co(OAc)₂ in acetonitrile at room temperature.     

Unexpected interconversion reaction of 1,4-diaminofullerenes

A facile substitution of amine groups attached to the fullerene cage occurs when 1,4-diaminofullerenes C60[NR2]2 are allowed to react with excess of another amine R'2NH; this reaction proceeds rapidly at room temperature without any additional initiators.     

Synthesis and Characterization of New CIS-1,4-Diaminocyclohexane and Piperidine Platinum(II) Complexes Containing Disubstituted Sulfide Groups

Abstract

A series of cationic platinum(II) complexes of the type [Pt(cis-1,4-DACH)(R′R″S)Cl]NO₃ and [Pt(PIP)₂(R′R″S)Cl]NO₃ (where cis-1,4-DACH = cis-1,4-diaminocyclohexane; PIP = piperidine; and R′R″S = dimethylsulfide, diethylsulfide, dipropylsulfide, diisopropylsulfide, dibutylsulfide, diphenylsulfide, dibenzylsulfide, methylphenylsulfide, or methyl-p-tolylsulfide) have been synthesized and characterized by elemental analysis and infrared, ¹H, and ¹⁹⁵Pt nuclear magnetic resonance spectroscopy.     

Novel solid-state synthesis of dimeric 4-aryl-1,4-dihydropyridines

On irradiation in the solid state the 4-aryl-1,4-dihydroypridines 1 undergo [2+2] cycloadditon to centrosymmetric head-to-tail dimers 3 and 4a . The almost exclusive formation of the cage dimers 3 via the C₂-symmetric syn-dimers 2 takes place in nearly quantitative yields, in contrast with the cycloaddition reaction of the anti-dimer 4a , which is accompanied by photooxidation to pyridine 5a .     

1-Butyl-3-methylimidazolium Hydrogen Sulfate [bmim]HSO4: An Efficient Reusable Acidic Ionic Liquid for the Formylation of Alcohols

1-Butyl-3-methylimidazolium hydrogen sulfate [bmim]HSO4 as an acidic ionic liquid was prepared and used as a catalyst for the formylation of alcohols with ethyl formate at room temperature with good to excellent yields. A good selectivity was observed for the formylation of primary alcohols in the presence of tertiary alcohols.     

ESR Studies on a Friedel‐Crafts Alkylation Reaction in [bmim]Cl‐AlCl3 Ionic Liquid

The paramagnetic complexes formed in Friedel‐Crafts alkylation reaction systems are invistigated by electron spin resonance (ESR) spectroscopy, in room temperature ionic liquids system 1‐butyl‐3‐methyl‐limidazolium chloride‐aluminium chloride ([bmim]Cl‐AlCl₃). The results indicate that ESR spectra observed are due to polycyclic aromatic radical cations formed from their parent hydrocarbons. ESR spectrum of spin adduct is obtained in an ionic liquid system composed of [bmim]Cl‐AlCl₃. In acidic solution the ¹⁴N hyperfine coupling constant of 4‐oxo‐TEMPO, 2.15 mT, is appreciably larger due to an adduct formed with AlCl₃.     

Synthesis and Properties of 1,3-Diaryl-5,6-dihydro-8H-imidazo[2,1-c]-1,4-oxazinium Bromides

It has been established that the condensation of 3-(4-methoxyphenylamino)-5,6-dihydro-2H-1,4-oxazine with substituted phenacyl bromides occurs at the exocyclic nitrogen atom with formation of 3-aryl-3-hydroxy-1-(4-methoxyphenyl)-2,5,6,8-tetrahydro-3H-imidazo[2,1-c]-1,4-oxazinium bromides. By treatment of the latter with acetic anhydride 3-aryl-1-(4-methoxyphenyl)-5,6-dihydro-8H-imidazo[2,1-c]-1,4-oxazinium bromides are formed. The structures of the compounds synthesized were determined via ¹H NMR spectroscopy and X-ray diffraction.     

室温离子液体促进的5-亚芳基巴比妥酸衍生物的合成

在室温离子液体1-丁基-3-甲基咪唑四氟硼酸盐([bmim]BF₄)存在下, 采用室温研磨和微波辐射的方法, 由芳香醛和巴比妥酸或硫代巴比妥酸经Knoevenagel缩合反应, 制备了相应的5-亚芳基巴比妥酸或5-亚芳烃基硫代巴比妥酸衍生物. 在室温研磨条件下反应2 h, 产率为78%～96%, 在微波辐射功率为160 W时反应20 s, 产率为82%～98%, 产物结构经¹H NMR确证.     

Synthesis of fluorinated 2,6-heptanediones and 2-oxa-6- azabicyclo[2.2.2]octanes from 1,4-dihydropyridines

Electrophilic fluorination of Hantzsch-type 1,4-dihydropyridines with Selectfluor^® led to the formation of new fluorinated 2,6-heptanediones - dialkyl 2,4-diacetyl-2,4-difluoro-3-phenylpentanedioates. Novel 2,6-heptanedione derivatives in reaction with hydrazine hydrate easily form 6-amino-4,7-difluoro-3-hydroxy-1,3-dimethyl-5-oxo-8-phenyl-2-oxa-6-azabicyclo[2.2.2]octanes instead of the corresponding diazepine derivatives. The obtained 2-оxa-6-azabicyclo[2,2,2]octanes are thermally stable at the temperatures below 50°С. At higher temperatures rearrangement of 2-oxa-6-azabicyclo[2,2,2]octanes offers new fluorine-containing pyrazolinone derivatives - alkyl esters of 2-fluoro-2-((4-fluoro-3-methyl-5-oxo-4,5-dihydro-1H-pyrazol-4-yl)(phenyl)methyl)-3-oxobutanoates.     

Effect of ionic liquid on polyaniline chemically synthesised under falling-pH conditions

This study investigates the effect of the ionic liquid 1-butyl-3-methyl imidazolium chloride ([bmim]Cl) on the morphological, structural, and electronic properties of polyaniline (PANI) products synthesised by the falling-pH method. Products were characterised by SEM, FT-IR, UVVIS, N₂-physisorption, and conductivity measurements. The [bmim]Cl addition strongly influenced the PANI morphology, specific surface area, porosity, and conductivity. Depending on the [bmim]Cl: ANI ratio and the synthesis pH, a wide range of PANI nanostructures could be prepared, with rod-like, and fibre-like elongated structures being the dominant morphology under most experimental conditions. Samples prepared in the presence of [bmim]Cl exhibit specific areas of ca 22–35 m² g^?1. The conductivity of the final products depends on the [bmim]Cl: ANI ratio. Temperature dependence of conductivity in the temperature range from 77 K to 300 K was also studied.     

Three-Component,One-Pot Synthesis of Benzo[b][1,4]oxazines in Ionic Liquid 1-Butyl-3-methylimidazolium Bromide

Benzo[b][1,4]oxazines have been synthesized in good to excellent yields in the presence of the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]Br under relatively mild conditions without any added catalyst, The method offers the advantages of good yields and short reaction times, and the ionic liquid can be easily separated from the product and reused.