scholarly journals Iron-catalysed enantioselective carbometalation of azabicycloalkenes

2021 ◽  
Author(s):  
Laksmikanta Adak ◽  
Masayoshi Jin ◽  
Shota Saito ◽  
Tatsuya Kawabata ◽  
Takuma Itoh ◽  
...  
Keyword(s):  
Optically Active ◽  
Iron Catalysis

The first enantioselective carbometalation reaction of azabicycloalkenes has been achieved by iron catalysis to in situ form optically active organozinc intermediates, which are amenable to further synthetic elaborations.

Asymmetrische Katalysen, 25 [1]. C5H5Mn(CO)2-Komplexe von optisch aktiven Chelatphosphanen als einzähnige Liganden in der enantioselektiven Katalyse / Asymmetric Catalyses, 25 [1]. C5H5Mn(CO)2 Complexes of Optically Active Chelate Phosphanes as Monodentate Ligands in Enantioselective Catalysis

1985 ◽  
Vol 40 (10) ◽  
pp. 1243-1249 ◽  
Author(s):  
Henri Brunner ◽  
Alfons Knott
Keyword(s):  
Cinnamic Acid ◽  
Enantioselective Hydrogenation ◽  
Optically Active ◽  
Enantioselective Catalysis ◽  
Dinuclear Complexes ◽  
Bidentate Ligands ◽  
Monodentate Ligand ◽  
Mononuclear Complexes ◽  
Monodentate Ligands

The chelate phosphanes Diphos, Diop, and Norphos were reacted with C5H5Mn(CO)2THF and CH3C5H4Mn(CO)2THF to give mononuclear complexes, containing the phosphanes as unidentate or as bidentate ligands, and dinuclear complexes, containing bridging phosphane ligands. In C5H5Mn(CO)2Diop one of the two P(C6H5)2 groups of Diop is coordinated to the C5H5Mn(CO)2 fragment; the uncoordinated P(C6H5)2 group makes it a monodentate ligand. C5H5Mn(CO)2Diop together with [Rh(cod)Cl]2 was used as an in situ catalyst in the enantioselective hydrogenation of (Z)-a-[N -acetam ino]cinnamic acid (78.4% ee) and in the enantioselective hydrosilylation of acetophenone with diphenylsilane (6.7% ee).

scholarly journals Underwater Use of a Hyperspectral Camera to Estimate Optically Active Substances in the Water Column of Freshwater Lakes

2020 ◽  
Vol 12 (11) ◽  
pp. 1745
Author(s):  
Michael Seidel ◽  
Christopher Hutengs ◽  
Felix Oertel ◽  
Daniel Schwefel ◽  
András Jung ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Water Column ◽  
Hyperspectral Imaging ◽  
Quality Parameters ◽  
Optically Active ◽  
Freshwater Lakes ◽  
Active Substances ◽  
Optically Active Substances

Freshwater lakes provide many important ecosystem functions and services to support biodiversity and human well-being. Proximal and remote sensing methods represent an efficient approach to derive water quality indicators such as optically active substances (OAS). Measurements of above-ground remote and in situ proximal sensors, however, are limited to observations of the uppermost water layer. We tested a hyperspectral imaging system, customized for underwater applications, with the aim to assess concentrations of chlorophyll a (CHLa) and colored dissolved organic matter (CDOM) in the water columns of four freshwater lakes with different trophic conditions in Central Germany. We established a measurement protocol that allowed consistent reflectance retrievals at multiple depths within the water column independent of ambient illumination conditions. Imaging information from the camera proved beneficial for an optimized extraction of spectral information since low signal areas in the sensor’s field of view, e.g., due to non-uniform illumination, and other interfering elements, could be removed from the measured reflectance signal for each layer. Predictive hyperspectral models, based on the 470 nm–850 nm reflectance signal, yielded estimates of both water quality parameters (R² = 0.94, RMSE = 8.9 µg L−1 for CHLa; R² = 0.75, RMSE = 0.22 m−1 for CDOM) that were more accurate than commonly applied waveband indices (R² = 0.83, RMSE = 13.2 µg L−1 for CHLa; R² = 0.66, RMSE = 0.25 m−1 for CDOM). Underwater hyperspectral imaging could thus facilitate future water monitoring efforts through the acquisition of consistent spectral reflectance measurements or derived water quality parameters along the water column, which has the potential to improve the link between above-surface proximal and remote sensing observations and in situ point-based water probe measurements for ground truthing or to resolve the vertical distribution of OAS.

Supported optically active poly(amide-imide) on magnetic graphene oxide/Fe3O4 for Hg2+ adsorption from aqueous solution

2019 ◽  
pp. 089270571988909
Author(s):  
Sedigheh Khalili ◽  
Zahra Rafiee
Keyword(s):  
Graphene Oxide ◽  
Sem Analysis ◽  
Optically Active ◽  
X Ray Diffraction ◽  
One Pot ◽  
Thermal Stabilities ◽  
Magnetic Graphene Oxide ◽  
Methyl Phenyl

The ternary superparamagnetic nanocomposites consisting of graphene oxide (GO), Fe3O4 nanoparticles, and optically active poly(amide-imide) (PAI) were fabricated in three steps consisting of a facile one-pot in situ growth of Fe3O4 on GO, resulted in the preparation of the magnetic Fe3O4@GO, modification of Fe3O4@GO by 3-aminopropyltriethoxy silane to introduce amino groups on its surface, and subsequently its compositing by various levels of 5, 10, and 15 wt% with chiral PAI derived from 3,5-diamino- N-(4-(di(1H-indol-3-yl)methyl)phenyl)benzamide and N, N′-(4,4′-carbonyldiphthaloyl)-bis-l-phenylalanine diacid through ultrasonic irradiation. Characterization of the resulting nanocomposites was performed by Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, scanning electron microscope (SEM), and thermogravimetric analysis (TGA). The SEM analysis showed Fe3O4 nanoparticles with 30 nm size successfully decorated the GO nanosheets. The TGA analysis established the expected thermal stabilities for PAI/Fe3O4@GO nanocomposites. Furthermore, incorporation of Fe3O4@GO in polymer matrix improved the mechanical properties substantially. PAI/Fe3O4@GO 10 wt% was used to evaluate the sorption properties of Hg2+ at pH 7.

Asymmetric α-Amination Reaction of Alkenoate Cyclic Esters Catalyzed by Chiral Tin Alkoxides

Synlett ◽  
2019 ◽  
Vol 30 (06) ◽  
pp. 738-742
Author(s):  
Akira Yanagisawa ◽  
Yoshiki Yamashita ◽  
Chika Uchiyama ◽  
Ryuta Nakano ◽  
Moe Horiguchi ◽  
...  
Keyword(s):  
Optically Active ◽  
Cyclic Esters ◽  
Amination Reaction ◽  
High Yields ◽  
Sodium Alkoxide

A catalytic enantioselective α-amination reaction of alkenoate cyclic esters with dialkyl azodicarboxylates was achieved by using a 3,3′-di(1-naphthyl)-substituted (R)-BINOL–dibromostannane complex as a chiral precatalyst in the presence of a sodium alkoxide and an alcohol. Optically active α-hydrazino ketones were obtained in moderate to high yields and with up to 91% ee in the presence of the chiral tin alkoxide generated in situ.

scholarly journals General Synthesis of Cyclopropanols via Organometallic Addition to 1-Sulfonylcyclopropanols as Cyclopropanone Precursors

2020 ◽  
Author(s):  
Roger Machín Rivera ◽  
Yujin Jang ◽  
Christopher M. Poteat ◽  
Vincent Lindsay
Keyword(s):  
Optically Active ◽  
Organometallic Reagents ◽  
Tertiary Alcohols ◽  
Mild Conditions ◽  
Synthetic Approaches ◽  
General Synthesis

The addition of organometallic reagents to ketones constitutes one of the most straightforward synthetic approaches to tertiary alcohols. However, due to the absence of a well-behaved class of cyclopropanone surrogates accessible in enantioenriched form, such a trivial synthetic disconnection has only received very little attention in the literature for the formation of tertiary cyclopropanols. In this work, we report a simple and high-yielding synthesis 1-substituted cyclopropanols via the addition of diverse organometallic reagents to 1- phenylsulfonylcyclopropanols, acting here as in situ precursors of the corresponding cyclopropanones.The transformation is shown to be amenable to sp, sp2 or sp3 -hybridized organometallic C-nucleophiles under mild conditions, and the use of enantioenriched substrates led to highly diastereoselective additions and the formation of optically active cyclopropanols.

scholarly journals Light-Emitting Polymer Nanocomposites

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Kyle Gipson ◽  
Brett Ellerbrock ◽  
Kathryn Stevens ◽  
Phil Brown ◽  
John Ballato
Keyword(s):  
Picolinic Acid ◽  
Optically Active ◽  
Inorganic Nanoparticles ◽  
Rare Earth Ions ◽  
Organic Ligands ◽  
Molar Ratio ◽  
Synthesis Process ◽  
Light Emitting ◽  
Rheological Measurements

Inorganic nanoparticles doped with optically active rare-earth ions and coated with organic ligands were synthesized in order to create fluorescent polymethyl methacrylate (PMMA) nanocomposites. Two different aromatic ligands (acetylsalicylic acid, ASA and 2-picolinic acid, PA) were utilized in order to functionalize the surface of Tb3+ : LaF3nanocrystals. The selected aromatic ligand systems were characterized using infrared spectroscopy, thermal analysis, rheological measurements, and optical spectroscopy. Nanoparticles producedin situwith the PMMA contained on average 10 wt% loading of Tb3+ : LaF3at a 6 : 1 La : Tb molar ratio and ~7 wt% loading of 4 : 1 La : Tb molar ratio for the PA and ASA systems, respectively. Measured diameters ranged from457±176 nm to150±105 nm which is indicative that agglomerates formed during the synthesis process. Both nanocomposites exhibited the characteristic Tb3+emission peaks upon direct ion excitation (350 nm) and ligand excitation (PA : 265 nm and ASA : 275 nm).

Second Order Nonlinear Optical Properties of Multifunctional Chiral Azobenzene Polymers

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Luigi Angiolini ◽  
Tiziana Benelli ◽  
Renato Bozio ◽  
Matteo Cozzuol ◽  
Loris Giorgini ◽  
...  
Keyword(s):  
Main Chain ◽  
Second Harmonic ◽  
Optically Active ◽  
Polymeric Films ◽  
Side Chain ◽  
Nlo Properties ◽  
Azobenzene Moiety ◽  
Corona Poling ◽  
Thermal Stability Of

AbstractCorona poling behaviours of optically active photochromic copolymers derived from methyl methacrylate (MMA) and the methacrylic ester of (S)-3- hydroxy pyrrolidine linked through the nitrogen atom to the highly conjugated photochromic 4'-(β-cyano-β-(methylsulfonyl)vinyl)-4-azobenzene moiety, have been investigated with the aim to evaluate the effect on the non-linear optical (NLO) properties originated by the presence of inactive side-chain MMA groups along the main chain. The NLO properties of in situ corona poled polymeric films have been studied by second harmonic generation (SHG) measurements. The d33 values of the investigated polymers were determined to be in the range 10-86 pm/V after corona poling. The temporal and thermal stability of the optimal SHG signals obtained after corona poling process of all the macromolecular materials has been investigated and compared. The results indicate that the maximum of these properties can be obtained at a molar content of photochromic units around 20- 40%.

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