Methylene Compounds Research Articles

Organoelectrocatalytic cyclopropanation of alkenyl trifluoroborates with methylene compounds

Cyclopropanes are not only privileged motifs in many natural products, agrochemicals, and pharmaceuticals, but also highly versatile intermediates in synthetic chemistry. As such, great effort has been devoted to the cyclopropane construction. However, novel catalytic methods for cyclopropanation with two abundant substrates, mild conditions, high functional group tolerance, and broad scope are still highly desirable. Herein, we report an intermolecular electrocatalytic cyclopropanation of alkenyl trifluoroborates with methylene compounds. The reaction uses simple diphenyl sulfide as the electrocatalyst under base-free conditions. And thus, a broad scope of various methylene compounds as well as vinyltrifluoroborates is demonstrated, including styrenyl, 1,3-dienyl, fluorosulfonyl, and base-sensitive substrates. Preliminary mechanistic studies are presented, revealing the critical role of the boryl substituent to facilitate the desired pathway and the role of water as the hydrogen atom source.

Construction of arylthio/arylamino methylene bonds by addition-elimination of nitroolefins with aromatic thiols and amines.

A highly efficient, catalyst-free, metal-free, atom economical green protocol for the synthesis of arylthio/arylamino methylene compounds by a Michael attack of arylthiols and anilines on nitroolefins derived from acenaphthaquinone and isatin has been developed. The method needs methanol as a reaction solvent and does not require any recrystallization, work-up process or column chromatography. (E)-Arylthio alkenes and (Z)-arylamino alkenes were obtained as the sole products. The results obtained from computational studies using density functional theory on ORCA program (B3LYP/def2-SVP level) are in good agreement with the data obtained from the single crystal X-ray analysis.

2+2+1+1] Cycloaddition Reaction of 1,3,5‐Triazinanes with Methylene Compounds: Approach to Hexahydropyrimidines

AbstractAn acetic acid‐catalyzed [2+2+1+1] cycloaddition of 1,3,5‐triazinanes with methylene compounds was developed. This protocol provides an access to hexahydropyrimidines (HHPs) (25 examples) in 35–99% yields under mild conditions in 2 hours. The potential application of this method was demonstrated by gram‐scale synthesis. Preliminary mechanistic investigation was conducted to elucidate the possible mechanism. This work represents the yet unknown example of [2+2+1+1] cycloaddition reaction between 1,3,5‐triazinanes and active methylene compounds.

Direct Cyclopropanations of Olefins with Methylene Compounds via Organoelectrocatalysis

Direct Cyclopropanations of Olefins with Methylene Compounds via Organoelectrocatalysis

Consecutive 2-azidoallylation/click cycloaddition of active methylene for synthesis of functionalized hepta-1,6-dienes with a bis-1,2,3-triazole scaffold

A tandem 2-azidoallylation/click cycloaddition reaction to access novel hepta-1,6-diene skelecton can be successfully accomplished with methylene compounds, phenolic substituted vinyl azide and alkynes in one pot.

Stereoselective Construction of Nitrile‐Substituted Cyclopropanes from 2‐Substituted Ethenesulfonyl Fluorides via Carbon‐Sulfur Bond Cleavage

AbstractThe intermolecular cyclopropanation of 2‐aryl and 2‐styryl substituted ethenesulfonyl fluorides with active cyano‐containing methylene compounds was described. This reaction proceeds via carbon‐sulfur bond cleavage under metal‐free conditions in up to 99% yield, affording a variety of nitrile‐substituted cyclopropanes with high diastereoselectivity.magnified image

Impact of Brønsted acid sites in MWW zeolites modified with cesium and amine species on Knoevenagel condensation

Abstract Layered zeolites of MWW family, MCM-22 and pillared MCM-36, were used as supports for base modifiers: cesium species (introduced via cation exchange or impregnation) and 3-aminopropyl trimethoxysilane (AP). The obtained materials were characterized by different methods (ICP-OES, N2 adsorption, XRD, XPS, TG/DTA, FTIR combined with pyridine adsorption, 2-propanol decomposition) for evaluation of chemical, structural and surface properties. All materials obtained were subjected to the Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate and ethyl acetoacetate. The effect of the zeolite structure, the stability of the catalysts as well as acid-base properties of zeolites on the activity in Knoevenagel condensation were considered. Of particular interest was the role of Bronsted acid sites (BAS). The nature of basic sites and BAS played different roles depending on the methylene compound used in the Knoevenagel condensation. AP-modified zeolites were the most active in the condensation between benzaldehyde and ethyl cyanoacetate, in which, in the first step of the reaction AP abstracted hydrogen from methylene carbon in ethyl cyanoacetate. A different reaction pathway was postulated for the condensation with ethyl acetoacetate on the basis of the highest activity of unmodified zeolites and the relationship between benzaldehyde conversion and the number of BAS. For this reaction protonation of benzaldehyde was postulated as the initial step of the reaction.

Catalytic advantages of NH2-modified MIL-53(Al) materials for Knoevenagel condensation reaction

The catalytic activity and stability of amino-based MIL-53(Al) materials were tested in Knoevenagel condensation of benzaldehyde with malononitrile reaction. The amine content was modulated by using different ratios of benzene-1,4-dicarboxylic acid (BDC) and 2-amino-benzene-1,4- dicarboxylic acid (NH2-BDC) as organic ligands for the synthesis. The amino-based MIL-53(Al) material synthesized with equimolar amounts of BDC and NH2-BDC (NH2(50%)-MIL-53(Al)) showed the best catalytic performance in terms of benzaldehyde conversion and benzylidenemalononitrile product yield. This equimolar ratio provided the best balance between the amount of amine basic sites and the pore size of the framework. The catalytic activity was also tested for several aldehydes with different molecular sizes and chemical substituents and ethyl cyanoacetate as another methylene compound. The NH2(50%)-MIL-53(Al) material also displayed a remarkable catalytic activity and stability compared to other amino-containing MOF materials (UiO-66-NH2, MIL-101(Al)-NH2 and IRMOF-3) and Na-exchanged beta zeolite. The NH2(50%)-MIL-53(Al) material was considerably active at 40 °C, being its catalytic performance enhanced when using methanol as solvent in the Knoevenagel condensation reaction. The reusability and stability of the NH2(50%)-MIL-53(Al) was shown by a set of five consecutive reaction cycles without appreciable loss of activity and high catalyst recoveries.

Controlled synthesis of graphitic carbon nitride and its catalytic properties in Knoevenagel condensations

Graphitic carbon nitride (g-C3N4) with high nitrogen content and surface area was synthesized by the thermal condensation of dicyandiamide and urea. This method gave a much higher product yield than the direct thermal decomposition of urea. The prepared g-C3N4 is active for the Knoevenagel condensation of an aldehyde or ketone with methylenic compounds, but the activity depends on the structure of basic nitrogen species. Fourier transform infrared and X-ray photoelectron spectroscopy show that at least four types of nitrogen species are present in g-C3N4, including primary amines (NH2), secondary amines (NH), tertiary nitrogen (N(C)3), and pyridinic nitrogen (CNC). The amounts and types of these nitrogen species in g-C3N4 are closely related to the urea/dicyandiamide ratio in its precursor mixture. The catalytic activity of these nitrogen species in the inactivated Knoevenagel condensation system decreases in the order of NH2>NH>N(C)3>CNC, while it is similar for the NH2 and NH species in the activated reaction system. This trend provides strong evidence for the abstraction of a proton from the methylenic compounds as the rate-determining step. The prepared g-C3N4 is highly stable and reusable in the Knoevenagel condensation reactions.

Bonding Structure and Mineral Analysis of Size Resolved Atmospheric Particles nearby Steelmaking Industrial Sites in Australia

Comprehensive understanding of organic and inorganic compounds in atmospheric particles of different size fractions ranging from coarse to ultrafine is essential for assessment of the impact of particles on the radiation balance. In this work the size resolved atmospheric particles were collected in the vicinity of three iron and steelmaking sites and one urban background site in Australia using an eight staged micro orifice uniform deposit impactor (MOUDI) sampler. The sampled particles were assessed using FTIR technique to determine the dominant functional groups, and XRD technique for determining the mineral content of the inorganic compounds. This study revealed variable distributions between and among bonding groups in urban and industrial areas. The hydroxyl (-OH) group (in alcohol compounds, surface OH on crystals, salt hydrate), aliphatic carbon (-CH_2) group (in methylene compounds, n-alkane), carbonyl (-CO) group (in acid halide, aryl carbonate, ketone, conjugated ketone), and amino (-NH_2) group (in primary amino compounds such as n-butylamine) in atmospheric particles were identified and most likely originated from combustion processes (industrial, transport, and domestic), sea spray, long range transport particles, and secondary organic particles sources nearby industrial and urban areas. Hematite mineral in the inorganic fraction of the atmospheric particles was found predominantly in the vicinity of the iron and steelmaking industries, which most likely originates from raw materials handling and process emissions.

A Simple and Efficient Procedure for Knoevenagel Reaction Promoted by Imidazolium-Based Ionic Liquids

Various room temperature ionic liquids (RTILs), notably, 1-methoxyethyl-3-methylimidazolium trifluoroacetate [MeOEtMIM]+[CF3COO]¯ , have been used to promote the Knoevenagel condensation to afford substituted olefins. All reactions proceeded effectively in the absence of any other catalysts or co-solvents with good to excellent yields. This method is simple and applicable to reactions involving a wide range of aldehydes and ketones with methylene compounds. The ionic liquid can be recycled without noticeable reduction of its catalytic activity. A plausible reaction mechanism is proposed. Keywords: Carbonyl compounds, catalysis, ionic liquids, Knoevenagel condensation, olefins.

Palladium nanoparticles supported on reduced graphene oxide as an efficient catalyst for the reduction of benzyl alcohol compounds

Palladium nanoparticles were prepared on reduced graphene oxide (Pd NPs/rGO) by using a sonochemical procedure. Pd NPs with a mean diameter of 37±22nm were deposited on reduced graphene oxide sheets by the reaction between PdCl42− and graphene oxide (GO) under sonochemical conditions. The catalyst was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The Pd NPs/rGO nanocomposite was successfully applied as a reusable catalyst for the reduction of benzyl alcohol derivatives into the corresponding methylene compounds in the presence of triethylsilane. The reductive dehydroxylation of benzyl alcohols takes place under mild conditions affording high yields of the corresponding methylene compounds in short reaction times.

Chemistry of Dimedone for Synthesis of Oxygen-, Nitrogen-, and Sulfur- Containing Heterocycles from 2-(3-Hydroxy-5,5-dimethylcyclohex-2-enylidene)malononitrile

A series of new oxygen-, nitrogen- and sulfur- containing spiro heterocycles was synthesized by reactions of 2-(3-hydroxy-5,5-dimethylcyclohex-2-enylidene)malononitrile with some active methylene and bidentate compounds.

2-Pyrrolidinecarboxylic Acid Ionic Liquid Catalyzed Knoevenagel Condensation

The pyrrolidinecarboxylic functionalized ionic liquid, 1-butyl-3-methylimidazolium-(S)-2-pyrrolidinecarboxylic acid salt ([bmim][Pro]), was prepared using an improved procedure. α,β-Unsaturated carbonyl compounds were selectively synthesized and high yields (88%–97%) were obtained at room temperature in aqueous media when [bmim][Pro] was used as the catalyst for the Knoevenagel reaction between a methylene compound and an aldehyde or ketone. [bmim][Pro] was reused six times without loss of catalytic activity. The catalytic mechanism is briefly discussed. 改进了 1-丁基-3-甲基咪唑 L-脯氨酸 ([bmim][Pro]) 功能化离子液体的合成路线, 并将该离子液体用于催化含活泼亚甲基化合物与醛或酮的 Knoevenagel 缩合反应. 在水介质中, 室温下, 该离子液体可快速催化上述 Knoevenagel 缩合反应, 并选择性生成 α,β-不饱和羰基化合物且分离收率可达到 88%–97%. 该脯氨酸离子液体循环重复使用 6 次后, 催化活性没有明显的下降. 此外, 初步探讨了其催化过程机理.

Enamines in Heterocyclic Synthesis: A Novel Simple and Efficient Route to Condensed Pyridazines

An efficient and easy preparation of enamine derivatives, via active methyl and methylene compounds by in situ-generated 1-(diethoxymethyl)piperidine, produced from the mixture of triethyl orthoformate/piperidine/DMF, are described. Some new pyridazinone derivatives have been synthesized from the reaction of enamines with hydrazine hydrate and cyanoacid hydrazide.

Molecular modelling studies on Arylthioindoles as potent inhibitors of tubulin polymerization

The crucial role played by microtubules in the life of eukaryotic cell makes tubulin an important route for the anticancer therapy. The Arylthioindoles (ATIs) along with the corresponding ketone and methylene compounds are potent tubulin assembly inhibitors. We are here reporting the result of a series of docking and molecular dynamics experiments on this series of compounds. The results obtained from our in silico studies not only provided us with an insight on the nature of the binding of the ATIs to tubulin, but were also at the core of the design of a new series of potent inhibitors of tubulin polymerization.

遷移金属錯体の酸・塩基作用を利用する触媒的不斉反応の開発

Acid-base catalysis of chiral transition metal complexes having hard anionic ligands such as hydroxo and acetate ligands is described. The Pd, Pt, Cu, and Ni complexes can effectively abstract the α-proton of methylene and methine compounds under non-basic conditions to give chiral enolates. In the case of 1,3-dicarbonyl compounds, the Pd complexes produced such enolates even under acidic conditions, and their cooperative action with protic acid to activate the various electrophiles including enones, imines, and acetals allows unique C-C bond-forming reactions to proceed with excellent enantioselectivity. Additionally, asymmetric protonation in aza-Michael reaction using the Pd hydroxo complex in combination with amine salt is described. For efficient activation of less acidic α-ketoesters, we developed a novel chiral nickel acetate complex, which is particularly effective to promote the asymmetric conjugate addition to nitroolefins. To confirm the utility of the reaction, its application to the asymmetric synthesis of MFPA was successfully demonstrated. Finally, the proposed reaction mechanisms of these reactions are briefly discussed.

Preparation of New Dialkyl Benzene-, Biphenyl-, and Naphthalene-bis(α-oxoethanedithioates)

Novel arene-bis- and -tris(α-oxoethanedithioate) esters of the benzene, the biphenyl, and, in particular, the naphthalene series were prepared by reaction of the corresponding diazoacetyl or bromoacetyl derivatives with elemental sulfur in the presence of triethylamine in dry DMF, and subsequent direct alkylation of the produced dithiocarboxylate anions. The thiolation reaction of the diazoketones was significantly promoted by the addition of anhydrous calcium chloride (calcium chloride–activated thiolation, or CAT). Certain carbonyl-activated methylene and methyl compounds exhibiting no bromo or diazo substituents could be also transformed into dithioesters by the CAT reaction. The structure of three dithioesters was corroborated by X-ray structural analyses. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

ChemInform Abstract: Study on the Syntheses of Polymethinecyanines. Part 1. The Reactions of 3-Phthalimido-2-propenal and Its Derivatives with Active Methyl and Methylene Compounds.

ChemInform Abstract: Study on the Syntheses of Polymethinecyanines. Part 1. The Reactions of 3-Phthalimido-2-propenal and Its Derivatives with Active Methyl and Methylene Compounds.

ChemInform Abstract: Facile Iodine(III)‐Induced Oxidative Cycloaddition of N‐Sulfonyl Imines with Methylene Compounds under Neutral Conditions.

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