Dimethyl Methyl Research Articles

Tandem transformations of bromo-substituted β-(methylsulfonyl)styrenes in reactions with dimethyl malonate, methyl cyanoacetate, and methyl acetoacetate

β-Bromo-β-(methylsulfonyl)styrene reacted with dimethyl malonate and methyl cyanoacetate in the presence of sodium hydride to give sulfonyl-substituted cyclopropanes, and sulfonyl-substituted 2,3-dihydrofuran was also formed in the reaction with methyl acetoacetate. Reactions of α-bromo-β-(bromomethylsulfonyl) styrene with dimethyl malonate and methyl cyanoacetate led to the formation of 2,3-dihydro-λ6-thiophene S,S-dioxide derivatives. In the reaction of α-bromo-β-(bromomethylsulfonyl)styrene with methyl acetoacetate, 2,3-dihydro-λ6-thiophene S,S-dioxide and 2,5-dihydro-λ6-thiophene S,S-dioxide derivatives and methyl acetoacetate O-alkylation product, methyl 3-[(E)-2-(bromomethylsulfonyl)-1-phenylvinyloxy]but-2-enoate, were obtained at a ratio of 2.7: 1.2: 1. α-Bromo-β-(methylsulfonyl)styrene reacted with dimethyl malonate to produce dimethyl 2-[2-(methylsulfonyl)-1-phenylethylidene]malonate. The reaction of β-bromo-β-(bromomethylsulfonyl) styrene with dimethyl malonate and methyl cyanoacetate were strictly stereoselective, and they afforded tetrahydro-λ6-thiophene S,S-dioxide derivatives. The reaction of the same substituted styrene with methyl acetoacetate was not stereoselective, and the products were two diastereoisomeric tetrahydro-λ6-thiophene S,S-dioxides and sulfonyl-substituted 2,3-dihydrofuran at a ratio of 2.3: 2.7: 1.

Nucleophilic Displacements in Alkylphosphonates: P–O Versus P–C Bond Cleavage. A Combined DFT and Experimental Study

Potential energy surfaces for the nucleophilic displacements at phosphorus in dimethyl methyl, chloromethyl, dichloromethyl, and trichloromethyl phosphonates have been computed by DFT methods. The results reveal that sequential introduction of chlorine substituents at the methyl group in methyl phosphonates increases the stability of transition states and intermediates, which facilitates P–C bond cleavage. While nonsubstituted dimethyl methylphosphonate may undergo exclusive P–O bond cleavage, the trichlorinated analogue reacts exclusively via P–C bond dissociation to form dichlorocarbene, which was trapped by various olefins to form the corresponding gem-dichlorocyclopropanes.

Synthesis and structures of the CH acid salts obtained in the reactions of malonic acid esters and malononitriles with 2,4,6-trinitrohalobenzenes in the presence of triethylamine

Reactions of dimethyl malonate, diphenyl malonate, methyl cyanoacetate, and malononitrile with 1-chloro-2,4,6-trinitrobenzene or 1-fluoro-2,4,6-trinitrobenzene in the presence of triethylamine in organic solvents gave stable brightly colored crystalline triethylammonium salts of the corresponding 2,4,6-trinitrophenylmalonic acid derivatives.

Reactions of styryl and phenylethynyl sulfones with some CH-acids

Reactions of methyl and p-tolyl phenylethynyl sulfones with enolated of dimethyl malonate and malononitrile lead to the formation of sulfonyl-substituted derivatives of ethylidenemalonic acid. Methyl (E)-β-styryl sulfone reacts with sodium enolates of dimethyl malonate, malononitrile, and methyl cyanoacetate to give common Michael adducts.

Synthesis and Characterization of a Novel Cyanate Ester Containing Dimethyl Benzene Linkage

A novel cyanate ester, dimethyl benzene cyanate ester (DMBCY), containing dimethyl benzene linkage, was synthesized from dimethyl benzene, methyl alcohol, formalin, and ClCN by a low-cost procedure. The resin was characterized by Fourier transform-infrared spectroscopy (FT-IR) and mass spectra (MS). The resin was cured with catalysts and studied by DSC. The thermal properties of the cured DMBCY were studied using DMA and TGA, and moisture absorption property was determined for the cured resin as well as its dielectric properties, flexural strength, and flexural modulus. The cured resin exhibited low dielectric constant (2.85), dissipation factor (2 × 10−4), and moisture absorption (0.43% after 48 h in 100°C).

Synthesis, identification and chemical features of high-purity trimethylselenonium iodide

High-purity (99.8%±1.1) trimethylselenonium iodide (TMSeI) was synthesized from dimethyl selenide and methyl iodide. Its chemical structure was confirmed using the spectroscopic methods of nuclear magnetic resonance, Fourier transform infrared and electrospray ionization-mass spectrometry. Some thermodynamic properties of the pure TMSeI were studied with differential scanning calorimetry, and its decomposition point and entropy were determined to be 157.7 °C and 100.7 kJ mol−1, respectively. The chromatographic and UV absorption behavior of the trimethylselenonium cation was also studied and the photochemical and chemical stability of TMSe+ and its decomposition products under varying microwave digestion conditions were examined. Some peculiar, yet interesting chemical properties on the stability of the compound were revealed. This is the first time that the chemical properties of this compound are comprehensively studied by various techniques and from different angles. The high purity of the synthesized compound allows it to be used as a primary standard compound in analytical method development and in basic and environmentally related studies.

ChemInform Abstract: Photoabsorption, Photoionization, and Neutral Dissociation Cross Sections of Dimethyl Ether and Ethyl Methyl Ether in the Extreme- Ultraviolet Range.

The absolute photoionization and neutral dissociation cross sections of dimethyl ether (CH3OCH3) and ethyl methyl ether (CH3CH2OCH3) in the 52–92 nm range have been obtained by measuring the absolute photoabsorption cross sections and photoionization quantum yields using a multistage ionization chamber and synchrotron radiation. A large deviation in the photoionization quantum yield of both molecules from unity, namely a noticeable enhancement of the neutral fragmentation cross sections, has shown that superexcited states exist densely in this wavelength range. Fluorescence excitation spectra of neutral dissociation fragments produced in the 35–100 nm photon impact on both molecules have also been measured by observing ultraviolet and vacuum ultraviolet emissions. A general appearance of the neutral dissociation cross sections correlates with the fluorescence excitation spectra from H(n=2), CH(A 2Δ), and CH3O(A). The superexcited states of dimethyl ether observed are shown to be purely repulsive states o...

ChemInform Abstract: Copper(I) Salt Mediated Arylation of Phosphinyl-Stabilized Carbanions and Synthetic Application to Heterocyclic Compounds.

The copper-mediated reaction of phosphinyl-stabilized carbanions 2a-c with aryl halides 1a-i in DMF or HMPA produced (arylmethyl)phosphonates 3-11 in good yields. Similar treatment of N-(2-iodophenyl)- and N-(2-iodophenyl)-N-methyl-α-(diethoxyphosphinyl)acetamides (12 and 14) led to 2-[(diethoxyphosphinyl)methyl]benzoxazole (13) and 1-methyl-3-(diethoxyphosphinyl)oxindole (15) in 71 and 85% yields, respectively. 4-(Ethorycarbonyl)-3,4-dihydroisoquinoline N-oxide (33) was synthesized by the reaction of ethyl α-(o-formylphenyl)acrylate (31), derived from 6 and paraformaldehyde, with hydrorylamine. The cycloaddition of 33 to olefins such as dimethyl maleate, methyl acrylate, and styrene was studied

ChemInform Abstract: Reactions of Selenothioic Acid S-Esters with Trivalent Phosphorus Compounds: New Synthetic Methods for α-Phosphoryl Alkyl Sulfides and Alkyl Selenides.

The reaction of selenothioic acid S-esters 1 with trialkyl phosphites proceeds smoothly with the extrusion of selenium atoms to afford α-phosphoryl sulfides 2 in good to high yields. A similar reaction takes place more easily with dimethyl phenylphosphonite and methyl diphenylphosphinite, although the ketene selenothioacetals 3 are also formed as by-products in increased yields. The use of diselenoic acid esters 1f and 1g gives α-phosphoryl selenides 2m and 2n. The products exhibit characteristic chemical shifts and coupling constants in their 31P NMR spectra. The structure of α-phosphoryl selenide 2n is confirmed by X-ray molecular structure analysis. The reaction with triphenylphosphine leads to oxidative dimerization of ester 1d to give divinyl diselenide 4 in good yield. A catalytic amount of triphenylphosphine is also effective to form divinyl diselenide 4. The reaction may begin with the nucleophilic attack of triphenylphosphine on the carbon atom of the selenocarbonyl group of ester 1d. Details of the reaction pathway leading to α-phosphoryl sulfides 2 are also discussed. The reaction with menthyl diphenylphosphinite 12 has suggested that the reaction may proceed via initial nucleophilic attack of trivalent phosphorus compounds bearing alkoxy groups on the selenium atom of esters 1. The intermediacy of phosphonium ylide 14 has also been supported by the reaction of the ester 1h which gives 1,4-oxathiane 15.

The Mechanism of Nucleophilic Displacements at Phosphorus in Chloro-Substituted Methylphosphonate Esters: P−O vs P−C Bond Cleavage: A DFT Study

Potential energy surfaces for the nucleophilic displacements at phosphorus in dimethyl methyl-, chloromethyl-, dichloromethyl-, and trichloromethylphosphonates have been computed at the B3LYP/6-31+G* level of theory, using IEF-PCM to account for the solvent effect. The results reveal that sequential addition of chlorine substituents on the methyl phosphonates increases the stability of transition states and intermediates which facilitate P-C bond cleavage. Thus, while nonsubstituted dimethyl methylphosphonate and dimethyl chloromethylphosphonate may undergo exclusive P-O bond cleavage, the trichlorinated analogue exclusively undergoes P-C bond dissociation. Dichloromethylphosphonic acid derivatives were found to be borderline cases: while P-O fission is the preferred process, P-C scission might also be feasible. The increase in stability of the corresponding transition states and intermediates can account for the enhancement in the apicophilicity of the methyl ligand upon substitution with chlorine atoms.

Spectroscopic Assignment of the FIR Laser Emissions Observed in Dimethyl Ether (CH3OCH3) and Methyl Fluoroform (CH3CF3)

By using the spectroscopic constants recently reported, it has been possible to assign many FIR transitions in dimethyl ether ( CH3OCH3) and methyl fluoroform (CH3CF3) that have been previously published in the scientific literature. Several of these assigned transitions have high quantum numbers and they can be used to improve the accuracy of the spectroscopic constants.

Tandem transformations of 10-substituted tetrahydrobenzo[b][1,6]naphthyridines resulted from the Michael addition of the nitrogen atom of the tetrahydropyridine fragment to the triple bond of activated alkynes

A reaction of 10-R-substituted tetrahydrobenzo[b][1,6]naphthyridines (R = CN, CONH2, Me) with dimethyl acetylenedicarboxylate, methyl and ethyl propiolates, and acetylacetylene has been studied. It was found that 1-acryloyl-10-cyanotetrahydrobenzo[b][1,6]naphthyridines are the major products of the reaction of alkyl propiolates with 10-cyano-substituted naphthyridines, whereas the reaction with 10-carbamoyl-substituted naphthyridines gives a mixture of 1-acryloyl-substituted naphthyridines and hexahydrobenzo[b]pyrido[3,4,5-d,e][1,6]naphthyridines. The latter are the only products in the reaction of 10-carbamoyl-substituted naphthyridines with acetylacetylene.

Isomerization and Fragmentation Reactions of Gaseous Dimethyl Phenylarsane Radical Cations and Methyl Phenylarsenium Cations. A Study by Tandem Mass Spectrometry and Density Functional Theory Calculations

The unimolecular reactions of the radical cation of dimethyl phenylarsane, C6H5As(CH3)2, 1*+ and of the methyl phenylarsenium cation, C6H5As+CH3, 2+, in the gas phase were investigated using deuterium labeling and methods of tandem mass spectrometry. Additionally, the rearrangement and fragmentation processes were analyzed by density functional theory (DFT) calculations at the level UBHLYP/6- 311+G(2d,p)//UBHLYP/5-31+G(d). The molecular ion 1*+ decomposes by loss of a .CH3 radical from the As atom without any rearrangement, in contrast to the behavior of the phenylarsane radical cation. In particular, no positional exchange of the H atoms of the CH3 group and at the phenyl ring is observed. The results of DFT calculations show that a rearrangement of 1*+ by reductive elimination of As and shift of the CH3 group is indeed obstructed by a large activation barrier. The MIKE spectrum of 2+ shows that this arsenium cation fragments by losses of H2 and AsH. The fragmentation of the trideuteromethyl derivative 2-d3+ proves that all H atoms of the neutral fragments originate specifically from the methyl ligand. Identical fragmentation behavior is observed for metastable m-tolyl arsenium cation, m-CH3C6H4As+H, 2tol+. The loss of AsH generates ions C7H7+ which requires rearrangement in 2+ and bond formation between the phenyl and methyl ligands prior to fragmentation. The DFT calculations confirm that the precursor of this fragmentation is the benzyl methylarsenium cation 2bzl+, and that 2bzl+ is also the precursor ion fo the elimination of H2. The analysis of the pathways for rearrangements of 2+ to the key intermediate 2bzl+ by DFT calculations show that the preferred route corresponds to a 1,2-H shift of a H atom from the CH3 ligand to the As atom and a shift of the phenyl group in the reverse direction. The expected rearrangement by a reductive elimination of the As atom, which is observed for the phenylarsenium cation and for halogeno phenyl arsenium cations, requires much more activation enthalpy.

Synthesis and Transformations of 5-Substituted 2-Aryl-7H-[1,2,4]triazolo[3,2-b][1,3]thiazin-7-ones and 2-Aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones

3-Aryl-1,2,4-triazole-5-thiones react with dimethyl acetylenedicarboxylate and methyl 3-phenyl-propynoate to afford the corresponding 5-substituted 2-aryl-7H-[1,2,4]triazolo[3,2-b][1,3]thiazin-7-ones. Treatment of 2-aryl-2,3-dihydro-4H-[1,3]thiazino[3,2-a]benzimidazol-4-ones with alkalies leads to formation of 3-(benzimidazol-2-ylsulfanyl)-3-arylpropionic acids, their reaction with methyl p-toluenesulfonate yields 1-(3-methyl-2-thioxo-2,3-dihydro-1N-benzimidazol-1-yl)-3-phenyl-2-propen-1-one, and oxidation with hydrogen peroxide gives benzimidazole-2-sulfonic acid and 3-aryl-2-propenoic acids.

Organic trace gases of oceanic origin observed at South Pole during ISCAT 2000

Volatile organic compounds (VOCs) were measured at the South Pole (SP) from late Austral spring to mid-summer 2000 as part of the Investigation of Sulfur Chemistry in the Antarctic Troposphere Program (ISCAT-2000). This paper focuses on VOCs that are directly emitted from the ocean, specifically dimethyl sulfide (DMS), methyl nitrate (CH3ONO2), methyl iodide (CH3I) and bromoform (CHBr3). A partial seasonal cycle of these gases was also recorded during the year following ISCAT-2000. During the summer, the SP periodically receives relatively fresh marine air containing short-lived oceanic trace gases, such as DMS( tE1 day). However, DMSwas not detected at the S P until January even though DMSemissions from the Southern Ocean typically start peaking in November and elevated levels of other ocean-derived VOCs, including CH3ONO2 and CHBr3, were observed in mid-November. We speculate that in November and December most of the DMSis oxidized before it reaches the S P: a strong correlation between CH3ONO2 and methane sulfonate (MSA), an oxidation product of DMS, supports this hypothesis. Based on a limited number of samples taken over the course of one year, CH3ONO2 apparently accumulates to a quasi-steady-state level over the SP in winter, most likely due to continuing emissions of the compound coupled with a lower rate of photochemical destruction. Oceanic emissions were concluded to be the dominant source of alkyl nitrates at the SP; this is in sharp contrast to northern high latitudes where total alkyl nitrate mixing ratios are dominated by urban sources. r 2004 Elsevier Ltd. All rights reserved.

3+2] Cycloaddition of Dimethyl Acetylenedicarboxylate, Methyl Acrylate, and Ethyl Acrylate to 4,5-Dihydro-5-methyl-3H-spiro[benz-2-azepine-3,1'-cyclohexane] N-Oxide

The cycloaddition of methyl acrylate and ethyl acrylate to 4,5-dihydro-5-methyl-3H-spiro[benz-2-azepine-3,1'-cyclohexane] N-oxide proceeds without either regiospecificity or stereospecificity. Eight geometrical isomers of spiro[isoxazolidino[3,2-a]benz-2-azepine-5,1'-cyclohexane] were formed, of which several were isolated as pure samples. The cycloaddition of dimethyl acetylenedicarboxylate proceeds stereoselectively, leading to spiro[isoxazolino[3,2-a]benz-2-azepine-5,1'-cyclohexane] with cis arrangement of the protons at C(7) and C(11b).

Photoresponsive peptide and polypeptide systems 15*: Synthesis of photo-crosslinkable poly(amino acid)s by watery process and its application as a reinforcement for polyion complex fibers

The present article described the synthesis of the coumarin-containing polypeptides using the water-soluble active ester method and the reinforcement of the polyion complex (PIC) fibers by the photochemical cross-linking between the polypeptide-pendant coumaryloxyacetyl groups. Two kinds of cationic polypeptides, poly(α,L-lysine) (PLL) and poly(α,L-ornithine) (PLO) were treated with (4-hydroxyphenyl)dimethyl sulfonium methyl sulfate ester in water to incorporate the photoreactive coumaryloxyacetyl groups into the side chain amino groups of the PLL and PLO. The contents of the photoreactive groups in the produced coumarin-containing polypepides were controlled by the molar ratios of the amino groups to the active ester. The resulting coumarin-containing cationic polypeptides were spun into the PIC fibers with the anionic polysaccharide gellan in water. The tensile strengths of the coumarin-containing PIC fibers were superior to those of the intact PLL- and PLO-gellan PIC fibers. The mechanical strength of the coumarin-containing PIC fibers further increased upon light-irradiation. From these results, we concluded that the hydrophobic interactions and the covalent cross-linking due to the photochemical dimerization between the coumaryloxyacetyl groups significantly contributed to reinforcement of the PIC fibers. The present results afford a new methodology to the PIC reinforcement that was achieved by the polymer modification reaction in watery process.

Metameric esters ketonization in the vapor phase over solid catalyst

Ketonization of metameric esters n-hexyl acetate and ethyl n-hexanoate was carried out in the vapor phase over Sn-Ce-Rh-O catalyst at 370°C and at 1 and 3 h-1 load. In both cases the main products were dimethyl ketone, dipentyl ketone and methyl pentyl ketone; however, the compositions and ratios of the products obtained from both esters were different. The transformation pathways of both esters were inferred based on the quantitative differences in the composition of the products. The ratios of the particular compounds obtained during transformation of both esters indicate that the reactions proceeded simultaneously - through β-ketoesters with partial thermal decomposition of esters and secondary condensation of the formed aldehydes. Also the way of creation of ketones resulting from secondary condensation was proposed.

Nitropyridines. 1. Hantzsch synthesis of nitropyridines and their quaternary salts

Previously unknown 1,4-dihydropyridines containing acetyl, amide, benzoyl, ester, and cyano groups together with a nitro group were synthesized with preparative yields by a two-component Hantzsch synthesis based on 2-nitro-1,3-diphenylpropenone and various enamines. The nitrodihydropyridines were aromatized with sodium nitrite in acetic acid. The quaternary salts of low-basicity pyridines were produced with dimethyl sulfate and methyl fluorosulfonate.

Diels-Alder Reactions of Vinyl Derivatives of [1]Benzothieno[3,2-b]furan

2-Vinyl- (2) and 3-vinyl[1]benzothieno[3,2-b]furan (3) react with dimethyl acetylenedicarboxylate, methyl propiolate, maleic anhydride, or acrylonitrile endo-selectively as dienes to afford new [1]benzothieno[3,2-b][1]benzofuran derivatives 7-20. cis-Anhydrides 13 and 18 were transformed into dimethyl esters 21 and 22, respectively. It was shown that the base-catalyzed hydrolysis of 13 and 18 is accompanied by rearrangement of double bond in 13 and cis/trans isomerization of carboxylic group. Diesters 21 and 22, and nitriles 20 and 24 were aromatized by treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Selective monodecarboxylation of [1]benzothieno[3,2-b][1]benzofuran-8,9-dicarboxylic acid (26) and [1]benzothieno[3,2-b][1]benzofuran-6,7-dicarboxylic acid (27) afforded [1]benzothieno[3,2-b][1]benzofuran-8-carboxylic acid (28) and [1]benzothieno[3,2-b][1]benzofuran-7-carboxylic acid (29), respectively.