- Bright, Multi-responsive, Sky-Blue Platinum(II) Phosphors Based on a Tetradentate Chelating Framework
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A new class of highly efficient and stable, blue-phosphorescent PtII complexes based on a tetradentate chelating framework has been found to exhibit highly sensitive and reversible responses to multiple external stimuli including temperature, pressure, and UV irradiation with distinct phosphorescent color switching—from blue to red or white. Intermolecular excimer formation is the main origin of this intriguing multi-response phenomenon. Highly efficient singlet-oxygen sensitization by the PtII compounds yields UV-light-induced phosphorescence enhancement and color switching.
- Liu, Lijie,Wang, Xiang,Wang, Nan,Peng, Tai,Wang, Suning
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- Production of Hydroxy Acids: Selective Double Oxidation of Diols by Flavoprotein Alcohol Oxidase
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Flavoprotein oxidases can catalyze oxidations of alcohols and amines by merely using molecular oxygen as the oxidant, making this class of enzymes appealing for biocatalysis. The FAD-containing (FAD=flavin adenine dinucleotide) alcohol oxidase from P. chrysosporium facilitated double and triple oxidations for a range of aliphatic diols. Interestingly, depending on the diol substrate, these reactions result in formation of either lactones or hydroxy acids. For example, diethylene glycol could be selectively and fully converted into 2-(2-hydroxyethoxy)acetic acid. Such a facile cofactor-independent biocatalytic route towards hydroxy acids opens up new avenues for the preparation of polyester building blocks.
- Fraaije, Marco W.,Martin, Caterina,Trajkovic, Milos
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p. 4869 - 4872
(2020/02/11)
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- Preparation of cis-Fused Tetrahydropyranyl Lactones via Palladium-Catalysed Cyclocarbonylation of Enediols
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The stereoselective palladium-catalysed cyclocarbonylation of hex-5-ene-1,4-diols affords cis-fused bicyclic lactones only. Ring-opening with N,O-dimethylhydroxylamine hydrochloride gives the corresponding Weinreb amides, and their subsequent recyclisation provides advanced synthons for the prospective synthesis of decarestrictine L. The relative configurations of all the prepared tetrahydropyrans are determined by NOESY. The attempted transformations of lactones into methyl ketones leads to an unexpected furan, the formation of which is discussed.
- Cintulová, Daniela,Slahú?ková, Monika,Pa?trnák, Juraj,Prónayová, Na?a,Szolcsányi, Peter
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supporting information
p. 755 - 762
(2017/02/15)
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- Comparison of “on water” and solventless procedures in the rhodium-catalyzed hydroformylation of diolefins, alkynes, and unsaturated alcohols
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Catalytic systems containing Rh(acac)(CO)2 or Rh/PAA (PAA?=?polyacrylic acid) and hydrophobic phosphine (PPh3) were used in the hydroformylation of diolefins, alkynes, and unsaturated alcohols under solventless and “on water” conditions. The total yield of dialdehydes obtained from 1,5-hexadiene and 1,7-octadiene reached 99%, and regioselectivity towards linear dialdehydes was higher in the “on water” system. The tandem hydroformylation-hydrogenation of phenylacetylene led to the formation of saturated aldehydes (3-phenylpropanal and 2-phenylpropanal) at 98% conversion with a good regioselectivity towards the linear aldehyde in the “on water” reaction. In contrast, solventless conditions appeared better in the hydroformylation of 1-propen-3-ol. 4-Hydroxybutanal, formed in this reaction with an excellent selectivity, was next transformed to tetrahydrofuran-2-ol via a ring-closure process. Cyclic products were also obtained in hydroformylation of 1-buten-3-ol. In reaction of undec-1-ol and 2-allylphenol linear aldehydes were formed with the yield 69–87%. The hydroformylation of 3-buten-1-ol performed under “on water” conditions showed very good regioselectivity towards a linear aldehyde, 5-hydroxypentanal. Further cyclization of the aldehyde to tetrahydropyran-2-ol was observed.
- Alsalahi,Trzeciak
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- Selective reduction of esters to aldehydes under the catalysis of well-defined NHC-iron complexes
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On a direct course to the aldehyde: Hydrosilylation catalyzed by a well-defined N-heterocyclic-carbene-iron complex under UV irradiation enabled the selective reduction of esters to aldehydes (see scheme; Bn=benzyl, Mes=mesityl). The low catalyst loading and very mild reaction conditions make this chemoselective transformation a promising alternative to the reduction of esters with diisobutylaluminum hydride. Copyright
- Li, Haoquan,Misal Castro, Luis C.,Zheng, Jianxia,Roisnel, Thierry,Dorcet, Vincent,Sortais, Jean-Baptiste,Darcel, Christophe
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supporting information
p. 8045 - 8049
(2013/08/23)
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- A concise approach to the spiroiminal fragment of marineosins
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A concise approach to the spiroiminal fragment of marineosins A and B is described. The key steps involve an acid-catalyzed N-acyliminium ion cyclization and a Vilsmeier-Haack type reaction with Tf2O. The Royal Society of Chemistry 2013.
- Li, Guang,Zhang, Xun,Li, Qi,Feng, Pengju,Shi, Yian
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supporting information
p. 2936 - 2938
(2013/07/25)
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- Selective photooxidation of diols with silica bound W10 O324 -
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The decatungstate anion W10 O324 - has been heterogenized on silica previously functionalized with different ammonium cations covalently bound to the surface of the solid support. These materials are investigated as photocatalysts for the oxygen-assisted oxidation of 1,3-butanediol and 1,4-pentanediol. Product distribution and adsorption experiments indicate that the polarity of the environment surrounding the photoactive anion plays a crucial role in controlling the adsorption of diols on the surface and, consequently, their reaction with the photoexcited decatungstate. Proper reaction conditions are found for obtaining more than 90% of 4-hydroxy-2-butanone from 1,3-butanediol and for stopping the oxidation of 1,4-pentanediol to 4-hydroxypentanal with good yield. The employed photocatalysts present a very good stability in repeated experiments.
- Maldotti,Molinari,Bigi
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p. 312 - 317
(2008/09/16)
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- Catalytic aerobic oxidation of diols under photo-irradiation: Highly efficient synthesis of lactols
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Aerobic oxidation of 1, n- and 1,ω-diols with (ON)Ru(salen) 1 as the catalyst was found to give the corresponding lactols in almost quantitative yields. Furthermore, in the oxidation of 2,2-dimethylalkane-1,ω-diols, less sterically hindered ω-alcohols were found to be preferentially oxidized when (ON)Ru(salen) 6 was used as the catalyst. n-Decanol was preferentially oxidized in the presence of 2,2-dimethylpropanol also by using 6 as the catalyst.
- Miyata, Atsushi,Furukawa, Mizuki,Irie, Ryo,Katsuki, Tsutomu
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p. 3481 - 3484
(2007/10/03)
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- New syntheses with magnesium hydride part 2: Pathways to new complex hydrides and aluminium hydride
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The reaction between autocatalytically prepared magnesium hydride (Tego Magnan) and aluminium halides in ethers generates a new class of reducing agents, i.e. magnesium aluminium hydridohalides. By choosing dioxane-1,4 as solvent a route to an aluminium hydride dioxane complex is opened. The new reducing agents show outstanding selectivity especially in the field of organosilicones, combined with a maximum of safety in their application.
- Knott, Wilfried
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p. 629 - 634
(2007/10/03)
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- Concise synthesis of cis- and trans-theaspirones via oxonium ion-initiated pinacol ring expansion
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The odoriferous principle of black tea has been produced from 2,2-dimethylcyclopentanone. The reaction sequence begins with 1,2-addition of 5-lithio-2-methyl-2,3-dihydrofuran to this ketone and immediate acid-catalyzed ring expansion of the resulting carbinols to a separable pair of spiro ethers. Individual conversion of these diastereomers to α,β-unsaturated ketones is followed by tandem condensation with the methyllithium-lithium bromide complex and oxidation with pyridinium chlorochromate.
- Paquette, Leo A.,Lanter, James C.,Wang, Hui-Ling
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p. 1119 - 1121
(2007/10/03)
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- Structural Definition of Early Lysine and Histidine Adduction Chemistry of 4-Hydroxynonenal
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The lipid peroxidation product trans-4-hydroxy-2-nonenal (HNE) has been implicated in the covalent modification of low-density lipoproteins (LDL) thought to contribute to the overaccumulation of LDL in the arterial wall in the initial stages of atherosclerosis. Proposals for the exact stuctures of "early" protein side-chain modifications until now have been based on indirect evidence. In this paper, the structures of first-formed His- and Lys-based adducts were elucidated by correlating NMR spectral properties with those obtained on models with reduced chiral center content, in some cases following hydride reduction. In this manner, we could confirm unambiguously the structure of a HNE-His imidazole(Nτ) Michael adduct, stabilized as a cyclic hemiacetal and isolated from a neutral aqueous 1:1 stoichiometry reaction mixture. In the case of Lys/amine reactivity, where an excess of amine is needed to avert HNE aldol condensation, the predominance of a 1:1 Michael adduct in homogeneous aqueous solution and a 1:2 Michael-Schiff base adduct under two-phase aqueous-organic conditions could be verified by isolation of the respective borohydride-reduced forms. The 1:2 adduct, shown to exist as the cyclic hemiaminal, could represent a stable lysine-based cross-link in certain protein microenvironments.
- Nadkarni, Durgesh V.,Sayre, Lawrence M.
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p. 284 - 291
(2007/10/03)
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- Stereoselective Substitution at Phenyl-Substituted γ-Lactols with Organometallic Compounds
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A variety of monosubstituted γ-lactols 4-6 were prepared in good yields by DIBAL reduction of the corresponding γ-lactones 1-3.The monophenyl-substituted lactols 4b-6b were transformed into disubstituted tetrahydrofuran derivatives by replacement of the hydroxyl group by the alkyl residue of organometallic compounds used as nucleophiles.The diastereoselectivity of the substitution was found to depend strongly on the substitution pattern of the γ-lactols.For the reaction of the 3- and 4-substituted derivatives 4b and 5b, respectively, good to excellent trans selectivity was observed, while the 5-substituted derivative reacted without any diastereoselectivity.These results were interpreted by means of the Felkin-Anh model. - Keywords: γ-Lactone / Reduction / γ-Lactol / Lewis acid / Tetrahydrofurans
- Schmitt, Andreas,Reissig, Hans-Ulrich
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p. 871 - 876
(2007/10/02)
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- Synthesis of some 2-cyanomethyltetrahydrofuran and 2-cyanomethyltetrahydropyran derivatives
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2-cyanomethyltetrahydrofuran and 2-cyanomethyltetrahydropyran derivatives, useful in the synthesis of 3(5)-aminopyrazoles and 5-aminoisoxazoles have been prepared starting from corresponding lactones, via DIBAL-H reduction to lactols, and olefination by Wittig reaction to α, β-unsatured cyanoderivatives. These undergo instantaneous cyclization to tetrahydrofuran and tetrahydropyran derivatives.
- Passarotti,Valenti,Ceriani,Grianti
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p. 150 - 152
(2007/10/02)
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- The Influence of Intramolecular Dynamics on Branching Ratios in Thermal Rearrangements
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1- and 2-phenylbicyclohex-2-enes-5-d undergo thermal rearrangement to give products, differing only in the location of the deuterium, in ratio of about 9:1, but with identical activation enthalphies.Similarly, opticallly active trans-2-methyl-1-(trans-2-phenylethenyl)cyclopropane is found to rearrange to enantiomeric methylphenylcyclopentenes that are formed in a 5.9:1 ratio but with virtually identicyl activation enthalphies.Barring repeated coincidence, these results do not seem to be explicable within the framework of statistical theories of unimolecular kinetics such as RRKM theory, transition state theory, and variational transition state theory.The possible influence of dynamic effects in these and other unimolecular reactions is discussed.
- Newmann-Evans, Richard H.,Simon, Reyna J.,Carpenter, B. K.
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p. 695 - 711
(2007/10/02)
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- Selective oxidation of primary hydroxy groups in primary-secondary diols
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The two-phase oxidation of primary-secondary diols with sodium hypochlorite, mediated by TEMPO, brings about selective oxidation at the primary position. Such 5 diols are oxidized to the corresponding hydroxyaldehydes.
- Siedlecka,Skarzewski,Mlochowski
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p. 2177 - 2180
(2007/10/02)
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- Regioselectivity in the Semiconductor-Mediated Photooxidation of 1,4-Pentanediol
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Optimum conditions have been established for the selective semiconductor-photocatalyzed oxidation by long-wavelength ultraviolet light of the primary alcohol functionality in 1,4-pentanediol.On platinized (2percent) TiO2 powder suspended in oxygenated aqueous (4 vol percent) acetonitrile, the initial rate ratio for oxidation of the primary/secondary alcohol site was > 7.Analysis of further oxidation products allowed for mechanistic delineation of the course of the semiconductor-mediated reaction.The selectivity is attributed to the essential role of adsorption, with the criticalphotoinduced electron transfer occurring at the surface of the irradiated particle.ZrO2 and SnO2 samples were much less active than TiO2 as photocatalysts.The effects of oxygen pressure, metal cocatalyst loading, and water content of acetonitrile are discussed.
- Fox, Marye Anne,Ogawa, Haruo,Pichat, Pierre
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p. 3847 - 3852
(2007/10/02)
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- Two Total Syntheses of Showdomycin and Related Studies
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After a series of model reactions, D-ribose (2) was reacted with 3-(triphenylphosphoranylidene)-2,5-pyrrolidinedione (8a) in THF at reflux to produce 3(E)-2(S),3(S),4(R),5-tetrahydroxy-1-pentylidene)-2,5-pyrrolidinedione (35) (75 percent).Subsequent cyclization of 35 using phenylselenyl chloride followed by hydrogen peroxide gave showdomycin (1) (13 percent) and epi-showdomycin (36) (41 percent).Using a similar strategy 2,3-O-isopropylidene-D-ribose (37b) was reacted sequentially with 1-(triphenylmethyl)-3-(triphenylphosphoranylidene)-2,5-pyrrolidinedione (8b), phenylselenyl chloride, hydrogen peroxide, and trifluoroacetic acid to give (1) (3 percent overall).
- Barrett, Anthony G. M.,Broughton, Howard B.,Attwood, Steven V.,Gunatilaka, A. A. Leslie
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p. 495 - 503
(2007/10/02)
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