- Two Unusual Trimers of Diketene
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Formation of two unknown, tricyclic trimers of diketene, 3 and 4, was observed in diketene solutions containing (CH3)3SiCl/NaI or TsOH.
- Ernest, Ivan,Fritz, Hans,Rihs, Grety
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- Synthesis and Enantioselective Baeyer-Villiger Oxidation of Prochiral Perhydro-pyranones with Recombinant E. coli Producing Cyclohexanone Monooxygenase
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Recombinant whole cells of Escherichia coli overexpressing Adnetobacter sp. NCIMB 9871 cyclohexanone monooxygenase (E.C. 1.14.13.22) have been utilized for the Baeyer-Villiger oxidation of prochiral perhydro-pyranones. The spatial limitations of the enzym
- Mihovilovic, Marko D.,Rudroff, Florian,Kandioller, Wolfgang,Gr?tzl, Birgit,Stanetty, Peter,Spreitzer, Helmut
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- Diastereoselective synthesis of cis-2,6-disubstituted perhydro-4-pyranones using elevated pressure hydrogenation
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A diastereoselective strategy for the synthesis of γ-pyrons was developed, starting from the Mg diacetonedicarboxylate complex. Initial cyclization with suitable anhydrides or acid chlorides, followed by hydrolytic decarboxylation leads to 2,6-disubstitut
- Mihovilovic, Marko D.,Spreitzer, Helmut
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- Unusual aluminum chloride-assisted conversion of isopropenyl acetate into 3-acetyl- and 3,5-diacetyl-2,6-dimethyl-4H-pyran-4-ones
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Reflux of isopropenyl acetate with an excess of AlCl3 in 1,2-dichloroethane affords 3,5-diacetyl-2,6-dimethyl-4H-pyran-4-one in 17% yield. The mild acidic cleavage of the latter (2% HCl, 20°C, 16 h) gives 3-acetyl-2,6-dimethyl-4H-pyran-4-one in 87% yield, whereas this reaction under more drastic conditions (17% HCl, reflux, 3 h) gives 2,6-dimethyl-4H-pyran-4-one in 61% yield.
- Novikov,Shestak,Denisenko
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- HAPPY Dyes as Light Amplification Media in Thin Films
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A series of 1H amorphous tri-phenyl pyridine (HAPPY) dyes have been synthesized from luminescent triphenyl-group-containing 2-methyl-6-styryl-substituted-4H-pyran-4-ylidene derivatives in reactions with benzylamine and investigated for suitability as solution-processable light-emitting medium components in thin films for amplified spontaneous emission (ASE). Conversion of a 4H-pyrane ring into a 1H-pyridine fragment enables aggregation-induced emission enhancement (AIEE) behavior in the target products and slightly increases thermal stability, glass transition temperatures, and ASE efficiency with PLQY up to 15% and ASE thresholds as low as 46 μJ/cm2 in neat spin-cast films, although thermal and photophysical properties are mostly dominated by the incorporated electron acceptors. Continued lasing parameter efficiency parameter improvement experiments revealed that no further optimization of HAPPY dyes by doping in polymer matrixes is required as the amplified spontaneous emission thresholds were lowest in pure neat films due to the AIEE phenomenon.
- Zarins, Elmars,Pervenecka, Julija,Misina, Elina,Bezvikonnyi, Oleksandr,Vembris, Aivars,Balodis, Karlis,Volyniuk, Dmytro,Grazulevicius, Juozas V.,Kokars, Valdis
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- A convenient synthesis of di- and trisubstituted γ-pyrones
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Treatment of ketodiynes or allenynones with hot aqueous acid results in the facile formation of di- or tri-substituted γ-pyrrones. The mechanism of this new process was established.
- Majetich,Zhang,Dreyer
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- The Generation of a Library of Bromodomain-Containing Protein Modulators Expedited by Continuous Flow Synthesis
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A continuous flow process delivering key building blocks for a series of BCP modulator libraries is reported. A dynamically mixed flow reactor emerged as a pivotal technology in both synthesis and isolation phases enabling the processing of slurries and suspensions while maintaining high productivity and reliability. Accordingly, the synthesis of common intermediates in flow were employed to further build a pyridazone-based library (36 compounds) aimed at improving lead compound potency and selectivity while further enabling structure-activity relationship studies of a new BCP modulator family.
- Filipponi, Paolo,Baxendale, Ian R.
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p. 2000 - 2012
(2016/04/26)
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- Interaction of acetonitrile with trifluoromethanesulfonic acid: Unexpected formation of a wide variety of structures
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Interaction of acetonitrile with trifluoromethanesulfonic acid has been studied by multinuclear NMR and ESI-MS. It has been found that the interaction results in formation of a great variety of different cations and neutral compounds which is controlled by the ratio of CH3CN to TfOH. In the presence of an excess of the acid (molar ratio 1:8-14) diprotonated N-acetylacetamidine 1 is formed as the major product, which eventually transforms into protonated acetamidine 3 and acetic acid 4. At molar ratio of (1:1-2) diprotonated 2,4-dimethyl-6-methylidene-3H-1,3,5-triazine 12, tautomer of the diprotonated trimethyl-s-triazine 11, becomes the main product at an early stage of the reaction and diprotonated 1-(dimethyl-1,3,5-triazin-2-yl) prop-1-en-2-ol 15 at a later stage. In the case of a large excess of acetonitrile (4-20:1) trication 17 is formed as a result of the interaction between 11 and 12 along with some oligomers [(CH3CN) 3]n (n = 4-12). The Royal Society of Chemistry 2012.
- Salnikov, George E.,Genaev, Alexander M.,Vasiliev, Vladimir G.,Shubin, Vyacheslav G.
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supporting information; experimental part
p. 2282 - 2288
(2012/04/10)
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- New pyran dyes for dye-sensitized solar cells
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Although ruthenium-based dyes have been extensively used in dye-sensitized solar cells (DSSCs) as photosensitizers, they have several shortcomings such as high costs and potential environmental toxicities. This has stimulated the development of highly efficient organic dyes as photosensitizers. We report the synthesis and photophysical, electrochemical and theoretical properties of novel pyran-based organic dyes (D1, D2, and D3) as well as their applications in DSSCs for the first time. The designed dyes possess a cyanoacrylic acid group as an acceptor and arylamine group as a donor group in a D-π-A configuration. The introduction of varying donor groups resulted in correspondingly different photophysical and electrochemical properties. The DSSCs fabricated using dye D1 showed the highest photovoltaic performance: a maximum incident photon-to-current conversion efficiency (IPCE) of 42%, a short-circuit current density (Jsc) of 4.76 mA cm-2, an open circuit voltage (Voc) of 0.68 V, and a fill factor (FF) of 0.67, corresponding to an overall conversion efficiency of 2.17% under 100 mW cm-2 irradiation. The synthesized dyes with a pyran chromophore and arylamine donor groups showed potentials for applications in DSSCs.
- Awuah, Samuel G.,Polreis, Jason,Prakash, Joshi,Qiao, Qiquan,You, Youngjae
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scheme or table
p. 116 - 122
(2012/04/23)
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- Introduction of adjacent oxygen-functionalities in dimethyl heptalenedicarboxylates
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The bromination of dimethyl 8-methoxy-1,6,10-trimethylheptalene-4,5- dicarboxylate (6; Scheme 2) with N-bromosuccinimide (NBS) in N,N-dimethylformamide (DMF) leads in acceptable yields to the corresponding 9-bromoheptalenedicarboxylate 10 (Table 1). Ether
- Rogano, Frank,Stojnic, Danijela,Linden, Anthony,Abou-Hadeed, Khaled,Hansen, Hans-Juergen
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experimental part
p. 1194 - 1215
(2011/09/14)
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- Reactions of fused and unfused α-pyrones with magnesium alkoxide, sodium alkoxide and water as the nucleophile: effects of chelation
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The reactions between a series of α-pyrones (two mono- and three fused) and the non-chelating base sodium alkoxide, the chelating base magnesium alkoxide and water as the nucleophile, have been studied.Aromatic and other products formed reflect the points of attack on the pyrone systems and when sodium methoxide is used the ensuing cyclisation is preferentially by aldol mechanisms.The employment of excess magnesium methoxide or ethoxide gives magnesium-chelated precursors and the nature of products now depends on these intermediates, and the protection afforded by such magnesium chelation to the reaction products.In the case of structures containing chelated β-keto ester features the chelates are screened from attack as aldol acceptors, but are effective Claisen acceptors.In such chelates an adjacent methylene is activated by further magnesium alkoxide to act as an aldol or Claisen donor.These contrasting aldol/Claisen reactivities, as between a non-chelating and a chelating base, are illustrated in the ensuing chemistry of the pyrones.Treatment with water releases the main carbon chain with decarboxylation, from which new products may form.
- Crombie, Leslie,Games, David E.,James, Alun W. G.
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p. 2715 - 2724
(2007/10/03)
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- Kinetic and Spectroscopic Studies on the Thermal Decomposition of 2,2,6-Trimethyl-4H-1,3-dioxin-4-one: Generation of Acetylketene
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Acetylketene is shown to be a reactive intermediate in thermolytic reactions of 2,2,6-trimethyl-4H-1,3-dioxin-4-one (the diketene-acetone adduct) via a series of kinetic studies.The uncatalyzed acetoacetylations of phenol, 1-butanol, and di-n-butylamine with the title dioxinone at 82-107 deg C are first-order reactions in which the rate-limiting step is the formation of acetylketene and acetone, presumably via a retro-Diels-Alder reaction.Isopropenyl acetoacetate is not an intermediate in the aforementioned reactions but also provides acetylketene when heated.Acetylketene was observed by FT-IR spectroscopy in an argon matrix.
- Clemens, Robert J.,Witzeman, Stewart J.
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p. 2186 - 2193
(2007/10/02)
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- Pyran Annelation: An Effective Route to a Tricyclic Dienone
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A new pyran annelation reaction was investigated. 2,6-Dimethyl-4H-pyran-4-one (2) was converted to 2((p-tolylsulfonyl)methyl)-6-methyl-4H-pyran-4-one (7) which was alkylated at the C-2 methylene position regioselectively, and the p-tolylsulfonyl group can be easily eliminated with an aluminium amalgam reduction.On the other hand the pyran-4-one ring was easily transformed into an 1,5-diketone derivative.By joining and applying these selective alkylations and transformations, tricyclic dienone 22 was effectively synthesized from 2.
- Yamamoto, Makoto,Iwasa, Seiji,Takatsuka, Kenichi,Yamada, Kazutoshi
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p. 346 - 349
(2007/10/02)
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- ALKYLATION OF ACTIVE HYDROGEN COMPOUNDS WITH ALLYLIC AND BENZYLIC ALCOHOLS UNDER CoCl2 CATALYSIS. A USEFUL SYNTHESIS OF GRIFOLIN
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CoCl2 is a useful catalyst for the condensation of allylic and benzylic alcohols with active hydrogen compounds.Under these neutral conditions orcinol and farnesol react to afford the antibiotic grifolin.
- Marquet, J.,Moreno-Manas, M.
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p. 173 - 176
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF SUBSTITUTED γ-PYRONES
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An efficient and general synthetic method for various 2-mono- and 2,6-disubstituted γ-pyrones has been developed.This utilizes the C-acylation (70-85percent) of β-methoxy-α,β-enone lithium enolates 4 by acid chlorides 3 followed by the acid-catalyzed cycl
- Koreeda, Masato,Akagi, Hiroshi
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p. 1197 - 1200
(2007/10/02)
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