Magnesium oxide nanotubes: synthesis,characterization and application as efficient recyclable catalyst for pyrazolyl 1,4-dihydropyridine derivatives

Magnesium oxide nanotubes were prepared by electrospinning technique. The nanocatalysts have been characterized by various sophisticated techniques, including XRD, SEM, and TEM. The activities of these NT catalysts are promoting pyrazolyl 1,4-dihydropyridine syntheses have been extensively investigated. Various advantages associated with these protocols simple workup procedure, short reaction times, high yields and reusability of the catalyst.     

The first 4-dialkylamino-1,2-dihydropyridine derivatives: synthesis and basic reactions

The first two 4-dialkylamino-1,2-dihydropyridine derivatives 4a and 4b are prepared in good yield by addition of n-butyllithium or t-butyllithium to 4-dimethylaminopyridine 1 followed by quench with diethylcarbonate. Compound 4a can be hydrolyzed under mild conditions providing 4-dihydropyridone 5, an interesting acceptor building block. On the other hand reaction of 4a with dimethyl acetylene dicarboxylate gives benzene derivative 7 via a cycloaddition-cycloreversion path.     

具有生物活性的1,4-二氢吡啶衍生物的水热法合成及结构表征

1,4-二氢吡啶衍生物具有很好的生理活性。在医学上用作心血管疾病的防治保健药物,不仅能治疗肠胃疾病、雷诺氏病、脂肪肝、中毒性肝炎,也有抗衰老、防早熟等作用,还可以用作治疗肺动脉高压和癫痫病的辅助药物[1-2]。近年又发现1,4-二氢吡啶衍生物不但是一类高效的钙拮抗剂,亦是一种绿色饲料添加剂。它的合成通常采用文献报道的Hantzsch法合成[3],即将干燥氨气通入乙酰乙酸乙酯与醛的混合溶液中。该反应时间长、操作复杂,且氨气易对环境造成污染。正因为此,越来越多的化学家和药物学家将有机合成的研究重点放在对环境无污染的绿色合成上。如…     

New synthesis of 5,6-benzindole

A method has been developed for the synthesis of linear 5,6-benzindole by reduction of N-acetyl-5,6-benzindoxyl with NaBH₄ and subsequent hydrolysis of the N-acetyl group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 779–780, June, 1987.     

A hantzsch 1,4-dihydropyridine synthesis producing an unusual by-product

The reaction of 2-acetyl-1-(2-chlorophenyl)-6-methylhept-1-en-3-one ( 2 ) with ethyl 3-aminocrotonate gave an unusual isomer of a 1,4-dihydropyridine ( 6 ), having an exocyclic double bond. The structure and stereochemistry of 6 was established with ¹H and ¹³C nmr spectroscopy.     

Acetalation studies-III: synthesis of 1,2:3,4:5,6-tri-O-isopropylidene-galactitol

Treatment of galactitol uith 2,2-dimethoxypropane in dimethylsulphoxide unexpeatedly yields the title triketal, containing a cis-dioxolane ring; the structure of the product has been confirmed by spectral measurements.     

Carbohydrate-based synthesis of crocacin: stereoselective Heck reaction of carbohydrate 5,6-ene- and 5,6-yne-derivatives with aromatic halides

The Heck reaction between a carbohydrate 5,6-ene derivative 9 and an aromatic halide exclusively gave rise to the β-carbohydrate-substituted trans-styrene derivative 8; while the corresponding Wittig reaction produced a cis/trans mixture in which the cis-isomer predominated. The application of the Heck reaction is described to synthesize the intermediate 5, commonly used in the synthesis of members of the crocacin family.     

A new compound constructed from Keggin anions and Cu-5,6-diamino-1,10-phenanthroline complexes: synthesis,structure, and characterization

A new inorganic–organic hybrid based on polyoxometalate, [Cu₂(daphen)₂(H₂O)₄(PW₁₁W^VO₄₀)]?·?6H₂O (1) (daphen?=?5,6-diamino-1,10-phenanthroline), was synthesized hydrothermally and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, and thermal analysis. Single-crystal X-ray diffraction analysis reveals that in 1 the Keggin anion [PW₁₂O₄₀]^4? is tetradentate, linking four Cu(II)-daphen fragments with its four terminal oxygen atoms in a plane; Cu²⁺ is coordinated by two terminal oxygen atoms of two [PW₁₂O₄₀]^4? anions, two water molecules, and two nitrogen atoms of the phen ring of a daphen, forming a polymeric layer. The 3-D architecture of the compound is further formed via hydrogen bonds between these layers. The daphen is bidentate chelating and does not participate in formation of hydrogen bonds. Redox of 1 was examined.     

Nanogibbsite: synthesis and characterization

Nanogibbsite was synthesized using a supersaturated Al(OH)(3) solution which was prepared by titration of AlCl(3) with NaOH at pH 4.6. Excess chloride ions in the system were stripped off by dialyzing the Al(OH)(3) suspension against distilled water. The dialysis step is critical for initiation of gibbsite crystallization or the Al(OH)(3) suspension would remain amorphous. Chloride ions seem to mask the seeding sites and so retard the overall process of gibbsite formation. When subjected to heat treatment, gibbsite→alumina conversion occurred by two mechanisms. Nanogibbsite→α-alumina phase transition occurred forming χ- and κ-alumina polymorphs.     

Studies in the synthesis of 5,6-benzoquinolines

2-Phenyl- 5,6-benzolepidines were synthesized by the condensation of arylidene-2-naphthylamines with acetone in the presence of hydrochloric acid. The influence of various substitutents in the aromatic aldehydes on the course of the reaction was studied. It was shown that the introduction of certain substituents, e.g. a nitro or methyl group into the ortho-position of the azomethine residue caused an appreciable lowering in the yield of arylbenzolepidine. A cyclic product could not be obtained when the aldehyde residue contained two methyl groups in the ortho-position. The reaction of 2,4,6-trimethylbenzylidene-2-naphthylamine with acetone under severe conditions afforded the adduct -mesityl--(2-naphthylamino)butanone.     

Regioselective synthesis of 4-alkylpyridines via 1,4-dihydropyridine derivatives from pyridine

N-Ethoxycarbonylpyridinium chloride ($\text{1}$) reacted with RCu·BF₃ at 4-position with almost complete regioselectivity (better than 99%) to afford the corresponding 1,4-dihydropyridine derivatives ($\text{2}$) in high yields (81≈94%). The dihydropyridines were readily oxidized by oxygen to give 4-alkylpyridines ($\text{4}$: 38≈68% yields).     

Three-component cascade reaction synthesis of polycyclic 1,4-dihydropyridine derivatives in water

An efficient and straightforward synthesis of polycyclic 1,4-dihydropyridine derivatives has been developed by reacting heterocyclic ketene aminals (HKAs) with 1,3-cyclohexanedione derivatives and a number of substituted salicylaldehyde, respectively, via three-component cascade reactions in water. This strategy provides an efficient and environmentally friendly approach for easy access to various new fused polycyclic 1,4-dihydropyridine derivatives without the need of organic solvents in moderate to good yields.     

Organocatalyzed highly efficient synthesis of densely functionalized pyrrole-fused 1,4-dihydropyridine derivatives

Abstract

An organo base catalyzed diverse pyrrole-fused 1,4-dihydropyridines were synthesized. This one-pot, three-component domino reaction of enamino imides, aromatic aldehydes, and malononitrile/ethyl cyanoacetate was achieved by 10?mol% of DMAP under refluxing ethanol. In addition, novel bis-pyrrole-fused 1,4-dihydropyridine derivatives were also prepared by using terephthalaldehyde as a linker instead of simple aromatic aldehydes. This transformation proceeds via Knoevenagel condensation/Michael addition and N-cyclization reaction sequence and have some salient features including the use of a cost-effective catalyst, short reaction time and high atom economy. Moreover, the reusability of the catalyst was also performed up to five runs without any significant loss in activity.     

Nanoparticle-cored dendrimers: synthesis and characterization

The synthesis and characterization of a group of new dendrimers-namely, nanoparticle-cored dendrimers (NCDs)-are described. These materials were obtained by the reduction of hydrogen tetrachloroaurate phase-transferred into toluene in the presence of Fréchet-type polyaryl ether dendritic disulfide wedges of generation 1-5. These materials, possessing nanometer-sized gold clusters at the core and dendritic wedges radially connected to the core by Au-S bonds, were analyzed by TEM and TGA, and by UV, IR, and NMR spectroscopies. The number of branching units connected to the core decreased with the generation of the dendritic wedge, and this number changed from 2.18/nm(2) for Au-G-2 to 0.27/nm(2) for Au-G-5. This result suggests that, in the higher-generation NCDs, a large fraction of the surface area of the metal cluster is not passivated and is therefore available for catalytic activity.     

Shamrock surfactants: synthesis and characterization

Two types of a new class of surfactants with three headgroups, which possess the general structure 1, have been prepared. Within structure 1, a central headgroup is connected to two flanking headgroups by hydrocarbon chains. The term "shamrock" is used to describe surfactants of structure 1, denoting their triple-headed character and reflecting the fact that shamrocks have leaflets in groups of three. The major lipophilic character of shamrock surfactants is provided by the two hydrocarbon chains linking the three headgroups and not by long-chain alkyl groups appended to the linking hydrocarbon chains or the headgroups. The new surfactants are 2a (2,2,15,15,28,28-hexamethyl-2,15,28-triazonianonacosane triiodide), 2b (2,2,15,15,28,28-hexamethyl-2,15,28-triazonianonacosane trichloride), 3a (O,O'-di-[10-(N,N,N-tripropylammonio)decyl]phosphorodithioate bromide), and 3b (O,O'-di-[10-(N,N,N-tributylammonio)decyl]phosphorodithioate bromide). Compound 14 (2,2,9,9,16,16-hexamethyl-2,9,16-triazoniaheptadecane triiodide) was prepared for comparison with 2a. Surfactants 2 and 3 were characterized in water by measurement of their Krafft temperatures and critical aggregation concentrations, and their aggregates were studied by 1H NMR spectroscopy, dynamic laser light scattering, and phase-contrast optical microscopy. Aqueous 2b was also studied by cryo-etch high-resolution scanning electron microscopy, which revealed irregularly shaped cells containing a complex matrix of surfactant. Coacervates were observed by optical microscopy upon the hydration of 2 and 3.     

Rapid synthesis and biological evaluation of 1,4-dihydropyridine derivatives containing a benzothiazolyl moiety

A series of N-(6-methylbenzothiazolyl)-2,3,5,6-tetrasubstituted-4-(aryl)-1,4-dihydropyridines were synthesized by reaction of 2-amino-6-methylbenzothiazole, aromatic aldehyde and active methylene compound in methanol by conventional, as well as, microwave irradiation (solvent free and solid support) methods. The microwave irradiation technique gives better yield and shorter reaction time. Among solid supported microwave irradiation better yields are obtained in acidic alumina as compared to silica, neutral alumina, and basic alumina. All compounds were tested for antibacterial and antifungal activities and results have been compared with standard drugs. Entomological activities were also tested. The results showed that a change in the substitution pattern in 1,4-dihydropyridine derivatives may cause a marked effect on their antimicrobial activity.