18409-46-6Relevant academic research and scientific papers
New 1,3-dithiol-2-ylidene donor-π-acceptor chromophores with intramolecular charge-transfer properties, and related donor-π-donor molecules: Synthesis, electrochemistry, X-ray crystal structures, non-linear optical properties and theoretical calculations
Moore, Adrian J.,Bryce, Martin R.,Batsanov, Andrei S.,Green, Andrew,Howard, Judith A. K.,McKervey, M. Anthony,McGuigan, Peter,Ledoux, Isabelle,Orti, Enrique,Viruela, Rafael,Viruela, Pedro M.,Tarbit, Brian
, p. 1173 - 1184 (1998)
New donor-π-acceptor chromophores 5a-c, 7a-c, 8a-c, 13a-c and 14b-c have been synthesised: substituted 1,3-dithiole derivatives span a range of donor abilities [viz. 4,5-dimethyl > 4,5-bis(methylsulfanyl) > 4,5-bis(methoxycarbonyl)], a conjugated ethylenic or oligoethylenic linker varies the central π-electron unit (one, two and four conjugated double bonds) and dicyanomethylene and N-cyanoimine groups are the acceptor units. Extended tetrathiafulvalene derivatives 15a-c have also been synthesised. The electronic absorption spectra of compounds 5,7,8 and 14 reveal a broad low-energy intramolecular charge-transfer band [λmax(MeCN) 354-533 nm] which shifts bathochromically with increasing donor strength of the dithiole ring, and with increasing length of the conjugative pathway. The solution redox properties of 5,7,8 and 14, studied by cyclic voltammetry, reveal a reversible one-electron oxidation wave, attributed to the formation of the radical cation of the 1,3-dithiol-2-ylidene moiety, and an irreversible one-electron reduction to form the radical anion located on the dicyanomethylene or N-cyanoimine groups. For the bis(dithiole) donors 15a-c a single two-electron redox wave is observed. The non-linear optical (NLO) properties of 7a-c and 14b have been determined using the EFISH technique: moderate NLO properties are observed for compounds 7a-c [μ.β(0) 85-112 × 10-48esu] whereas for the more extensively conjugated compound 14b, the value is increased to μ.β(0) 1170 × 10-48 esu. The molecular structure and electronic properties of the unsubstituted (R = H) compounds 7, 8, 14 and 15 have been calculated within the density functional theory approach. The minimum energy conformation corresponds to the trans orientation of the side chain for 7, and the cis orientation for 8, in agreement with X-ray crystal structures and solution NMR data. The redox properties and electronic spectra are discussed on the basis of molecular orbital energies and topologies. The X-ray crystal structures of compounds 7b, 8b and 15b are reported. In 7b the 1,3-dithiol-2-ylidene and dicyanopropene systems are planar and form an angle of 3° between each other; the 'butadiene' unit has a trans configuration. Molecule 8b is planar (with the exception of the methyl groups) and the imine nitrogen atom is in a syn orientation towards the dithiole group, forming a short intramolecular S ... N contact [2.719(6) A]. For both 7b and 8b π-delocalisation is observed within the central conjugated spacer unit. Molecule 15b has a predominantly planar structure, with the central tetraene unit in an all-trans configuration.
Oxidation of Furans with Dimethyldioxirane. Interception of Malealdehyde and Related Aldehydes via Wittig Reactions
Adger, Brian J.,Barrett, Collette,Brennan, Joseph,McGuigan, Peter,McKervey, M. Anthony,Tarbit, Brian
, p. 1220 - 1222 (1993)
Unsaturated aldehydes including malealdehyde, generated in acetone by oxidation of furans with dimethyldioxirane, can be trapped efficiently by phosphoranes in Wittig reactions.
SIMPLE SYNTHESES OF ISOMERS OF MUCONALDEHYDE AND 2-METHYLMUCONALDEHYDE
Golding, Bernard T.,Kennedy, Gordon,Watson, William P.
, p. 5991 - 5994 (1988)
Periodate oxidation of cis-1,2-dihydrocatechol (3a) affords (Z,Z)-muconaldehyde (2b), wich can be readily converted (thermolysis and triethylamine catalysis, respectively) into its (E,Z)- (2c) and (E,E)-isomer (2a).Similarly, cis-1,2-dihydro-3-methylcatechol (3b) gives (Z,Z)-2-methylmuconaldehyde (2d) and thence (E,E)-2-methylmuconaldehyde (2c).
Stereoselective organocatalytic oxidation of alcohols to enals: A homologation method to prepare polyenes
Chen, Xiaobei,Zhang, Yinan,Wan, Huixin,Wang, Wei,Zhang, Shilei
supporting information, p. 3532 - 3535 (2016/03/04)
A novel method for organocatalytic oxidation through oxidative enamine catalysis was developed with excellent compatibility for the direct syntheses of enals from simple saturated alcohols. By using this amine-catalyzed IBX-oxidation, a wide range of aromatic and aliphatic substituted enals were successfully generated in high yields and exclusively stereoselective E-geometry. Moreover, varying the solvents and/or the loading amounts of IBX allowed for the selective oxidation of alcohols and aldehydes. Importantly, the homologous application of this method provided a selective and efficient way of preparing various highly sensitive conjugated polyene frameworks, which are enriched in natural products.
Evidence for the formation of Michael adducts from reactions of (E,E)-muconaldehyde with glutathione and other thiols
Henderson, Alistair P.,Bleasdale, Christine,Delaney, Kirsty,Lindstrom, Andrew B.,Rappaport, Stephen M.,Waidyanatha, Suramya,Watson, William P.,Golding, Bernard T.
, p. 363 - 373 (2008/02/04)
Glutathione induces the rapid isomerization of (Z,Z)-muconaldehyde to (E,E)-muconaldehyde via (E,Z)-muconaldehyde, probably via reversible Michael addition of the thiol to one of the enal moieties of the muconaldehyde. Reactions of (E,E)-muconaldehyde with glutathione (in the presence and absence of equine glutathione S-transferase), phenylmethanethiol, N-acetyl-l-cysteine, and N-acetyl-l-cysteine methyl ester were investigated using mass spectrometric techniques. In each case, evidence was obtained for the formation of Michael adducts, e.g., reaction between (E,E)-muconaldehyde and glutathione gave 4-glutathionyl-hex-2-enedial and 3,4-bis-glutathionyl-hexanedial. These experiments suggest that (Z,Z)-muconaldehyde, a putative metabolite of benzene, could lead to the long established urinary metabolite of benzene, (E,E)-muconic acid, via glutathione-mediated isomerization to (E,E)-muconaldehyde.
OH-initiated oxidation of benzene part II. Influence of elevated NOx concentrations
Klotz, Bjoern,Volkamer, Rainer,Hurley, Michael D.,Andersen, Mads P. Sulbaek,Nielsen, Ole John,Barnes, Ian,Imamura, Takashi,Wirtz, Klaus,Becker, Karl-Heinz,Platt, Ulrich,Wallington, Timothy J.,Washida, Nobuaki
, p. 4399 - 4411 (2007/10/03)
The present work represents a continuation of part I of this series of papers, in which we investigated the phenol yields in the OH-initiated oxidation of benzene under conditions of low to moderate concentrations of NOx, to elevated NOx levels. The products of the OH-initiated oxidation of benzene in 700-760 Torr of N2/O2 diluent at 297 ± 4 K were investigated in 3 different photochemical reaction chambers. In situ spectroscopic techniques were employed for the detection of products, and the initial concentrations of benzene, NOx, and O2 were widely varied (by factors of 6300, 1500, and 13, respectively). In contrast to results from previous studies, a pronounced dependence of the product distribution on the NOx concentration was observed. The phenol yield decreases from approximately 50-60% in the presence of low concentrations (x to values below 5% in the presence of extremely high (>10 000 ppb) NOx concentrations. In the presence of high concentrations of NOx, the phenol yield increases with increasing O2 partial pressure. The rate constant of the reaction of hydroxycyclohexadienyl peroxyl radicals with NO was determined to be (1.7 ± 0.6) x 10-11 cm3 molecule-1 s-1. This reaction leads to the formation of E,E-2,4-hexadienedial as the main identifiable product (29 ± 16%). The reaction of the hydroxycyclohexadienyl radical with NO2 gave phenol (5.9 ± 3.4%) and E,E-2,4-hexadienedial (3.4 ± 1.9%), no other products could be identified. The residual FTIR product spectra indicate the formation of unknown nitrates or other nitrogen-containing species in high yield. The results from the present work also show that experimental studies aimed at establishing/verifying chemical mechanisms for aromatic hydrocarbons must be performed using NOx levels which are representative of those found in the atmosphere.
Gas-phase reaction of OH radicals with benzene: Products and mechanism
Berndt,Boege
, p. 4946 - 4956 (2007/10/03)
Benzene and a series of alkylated derivatives (toluene, xylenes, etc.) are predominantly emitted into the atmosphere by human activities (traffic, solvent use). The gas-phase reaction of OH radicals with benzene was studied in O2/He mixtures under flow conditions at 276-353 K and at 100 and 500 mbar using on-line FTIR spectroscopy and GC-MS measurements. Under conditions of a predominant reaction of the OH/benzene adduct with O2, the product formation was evaluated for variable NO concentrations. Identified products were the isomers of hexa-2,4-dienedial, phenol, nitrobenzene, p-benzoquinone and glyoxal. For increasing NO concentrations, there was a decrease of the phenol yield and the yields of trans,trans-hexa-2,4-dienedial and nitrobenzene increased. A reaction scheme was proposed describing the formation of phenol, nitrobenzene (upper limit), the hexa-2,4-dienedials and other products (unidentified carbonylic substances, etc.). The model allowed to predict formation of the different products in dependence on temperature and NOx concentration.
Atmospheric chemistry of benzene oxide/oxepin
Klotz, Bjoern,Barnes, Ian,Becker, Karl H.,Golding, Bernard T.
, p. 1507 - 1516 (2007/10/03)
The atmospheric chemistry of benzene oxide/oxepin, a possible intermediate in the atmospheric oxidation of aromatic hydrocarbons, has been investigated in a large volume photoreactor at 298 K and atmospheric pressure using in situ FTIR spectroscopy for the analysis. Rate coefficients of (10.0 ± 0.4) × 10-11 and (9.2 ± 0.3) × 10-12 cm3 molecule-1 s-1 have been determined for the reaction of benzene oxide/oxepin with OH and NO3 radicals, respectively. Reaction with OH radicals produces almost exclusively the (E,Z)- and (E,E)-isomers of hexa-2,4-dienedial, whereas reaction with NO3 produces (Z,Z)-hexa-2,4-dienedial and unidentified organic nitrates. Phenol has been observed as a major product of the thermal decomposition, visible and UV photolysis of benzene oxide/oxepin. The results are discussed in conjunction with the oxidation mechanisms of aromatic hydrocarbons. The major atmospheric sinks of benzene oxide/oxepin will be reaction with OH radicals and photolysis and, under smog chamber conditions with high NO2 concentrations, also reaction with NO3.
Prototypes for the polaronic ferromagnet. Synthesis and characterization of high-spin organic polymers
Murray, Michael M.,Kaszynski, Piotr,Kaisaki, David A.,Chang, Wonghil,Dougherty, Dennis A.
, p. 8152 - 8161 (2007/10/02)
Preparation and characterization of several new polymers (1-7) that are considered one-dimensional prototypes for the polaronic ferromagnet are reported. Synthesis involved either Wittig or Suzuki coupling to produce polymers with extended π systems. Oxid
Palladium-Catalyzed Reductive Coupling of Acid Chlorides with β-Stannyl Enones: Synthesis of 1,4-Diketones and Mechanistic Aspects
Echavarren, Antonio M.,Perez, Marta,Castano, Ana M.,Cuerva, Juan M.
, p. 4179 - 4185 (2007/10/02)
The palladium-catalyzed coupling of acid chlorides with (E)-1,2-bis(tri-n-butylstannyl)ethene or β-stannyl enones gives butane-1,4-diones directly by reduction of the intermediate enedicarbonyl intermediate.The double bond conjugated with a single carbonyl group was not significantly reduced.The generality of the method is illustrated by two syntheses of the 1,4-diketone ipomeanine.By performing the reaction at lower temperatures, α,β-unsaturated 1,4-diketones can also be prepared.The reduction of the intermediate α,β-unsaturated 1,4-diketones probably proceeds by insertion of a palladium hydride, formed in situ by reaction of a Pd(II) complex with Bu3SnCl, followed by hydrolysis of the intermediate palladium enolate.
