Synthetic and structural considerations on highly curved bowl-shaped fragments of fullerenes

2014 ◽  
Vol 86 (4) ◽  
pp. 539-544 ◽  
Author(s):  
Yao-Ting Wu ◽  
Tsun-Cheng Wu ◽  
Min-Kuan Chen ◽  
Hsin-Ju Hsin
Keyword(s):  
Molecular Geometry ◽  
Transition Structure ◽  
X Ray ◽  
Mild Conditions ◽  
Polar Crystals ◽  
Metal Catalyzed ◽  
Planar Transition ◽  
Orbital Axis

AbstractNumerous highly curved fragments of C60 and unique subunits of C70 were synthesized under mild conditions using metal-catalyzed protocols. According to X-ray crystallographic analyses, highly curved fragments of C60 have a maximum π-orbital axis vector (POAV) pyramidalization angle of up to 12.9 °, whereas distinctive fragments of C70, analogous to the tube portion of the rugby-shaped buckyball, are less curved. Among the eight buckybowls studied herein, five form polar crystals. Depending on the molecular geometry, the inversion dynamics of buckybowls involves either a planar or an S-shaped (non-planar) transition structure.

An unusual reaction of a bridged triterpenoid α-diketone with acetic anhydride

1991 ◽  
Vol 56 (12) ◽  
pp. 2917-2935 ◽  
Author(s):  
Eva Klinotová ◽  
Václav Křeček ◽  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Jaroslav Podlaha ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Acetic Anhydride ◽  
Spectral Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mild Conditions ◽  
Condensation Products ◽  
Unsaturated Lactones ◽  
C Nmr

3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) reacts with acetic anhydride in pyridine under very mild conditions affording β-lactone IVa and γ-lactones Va and VIIa as condensation products. On reaction with pyridine, lactones Va and VIIa undergo elimination of acetic acid to give unsaturated lactones VIIIa and IXa, respectively. Similarly, the condensation of 20β,28-epoxy-21,22-dioxo-18α,19βH-ursan-3β-yl acetate (IIIb) with acetic anhydride leads to β-lactone IVb and γ-lactone Vb; the latter on heating with pyridine affords unsaturated lactone VIIIb and 21-methylene-22-ketone Xb. The structure of the obtained compounds was derived using spectral methods, particularly 1H and 13C NMR spectroscopy; structure of lactone IVa was confirmed by X-ray diffraction.

Asymmetric Synthesis of α-Alkylated γ-Lactam via Nickel/8-Quinim-Catalyzed Reductive Alkyl-Carbamoylation of Unactivated Alkene

Synlett ◽  
2021 ◽  
Author(s):  
Xianqing Wu ◽  
Mohini Shrestha ◽  
Yifeng Chen
Keyword(s):  
Functional Group ◽  
Enantioselective Synthesis ◽  
Chiral Auxiliary ◽  
Alkyl Iodide ◽  
General Strategy ◽  
Chemical Bonds ◽  
Mild Conditions ◽  
Chiral Carbon ◽  
Enantioselective Reaction ◽  
Metal Catalyzed

AbstractChiral-auxiliary-mediated synthesis represents the most frequently used synthetic tool for the induction of chirality on α-position of γ-lactams in organic synthesis. However, the general strategy requires the stoichiometric use of chiral reagents with multiple manipulation steps. Transition-metal-catalyzed asymmetric alkene dicarbofunctionalization using readily available substrates under mild conditions allows the simultaneous construction of two vicinal chemical bonds and a chiral carbon center, hence, gain expedient access to chiral heterocycles. Herein, we disclose a Ni-catalyzed enantioselective reaction of 3-butenyl carbamoyl chloride and primary alkyl iodide enabled by a newly designed chiral 8-quinoline imidazoline ligand (8-Quinim). This protocol features broad functional group tolerance and high enantioselectivities, achieving unprecedented synthesis of chiral nonaromatic heterocycles via catalytic reductive protocol.1 Introduction2 Development of 8-Quinim Ligand3 Nickel/8-Quinim-Catalyzed Enantioselective Synthesis of Chiral α-Alkylated γ-Lactam4 Conclusion and Outlook

scholarly journals Towards a unified understanding of the copper sites in particulate methane monooxygenase: An X-ray absorption spectroscopic investigation

2021 ◽  
Author(s):  
George Cutsail III ◽  
Matthew O Ross ◽  
Amy C Rosenzweig ◽  
Serena DeBeer
Keyword(s):  
Greenhouse Gas ◽  
Spectroscopic Investigation ◽  
Liquid Fuel ◽  
Methane Monooxygenase ◽  
Enzymatic Conversion ◽  
Particulate Methane Monooxygenase ◽  
X Ray ◽  
Mild Conditions ◽  
Copper Sites ◽  
X Ray Absorption

The enzymatic conversion of the greenhouse gas, methane, to a liquid fuel, methanol, is performed by methane monooxygenases (MMOs) under mild conditions. The copper stoichiometry of particulate MMO (pMMO) has...

scholarly journals High-Active Metallic-Activated Carbon Catalysts for Selective Hydrogenation

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Nicolás Carrara ◽  
Carolina Betti ◽  
Fernando Coloma-Pascual ◽  
María Cristina Almansa ◽  
Laura Gutierrez ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Selective Hydrogenation ◽  
Nickel Catalysts ◽  
Metallic Phase ◽  
Hydrogen Chemisorption ◽  
Electronic Effects ◽  
X Ray ◽  
Mild Conditions ◽  
Temperature Programmed ◽  
Carbon Catalysts

A series of low-loaded metallic-activated carbon catalysts were evaluated during the selective hydrogenation of a medium-chain alkyne under mild conditions. The catalysts and support were characterized by ICP, hydrogen chemisorption, Raman spectroscopy, temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR micro-ATR), transmission electronic microscopy (TEM), and X-ray photoelectronic spectroscopy (XPS). When studying the effect of the metallic phase, the catalysts were active and selective to the alkene synthesis. NiCl/C was the most active and selective catalytic system. Besides, when the precursor salt was evaluated, PdN/C was more active and selective than PdCl/C. Meanwhile, alkyne is present in the reaction media, and geometrical and electronic effects favor alkene desorption and so avoid their overhydrogenation to the alkane. Under mild conditions, nickel catalysts are considerably more active and selective than the Lindlar catalyst.

scholarly journals X-RAY DETERMINATION OF THE STRUCTURE OF ANHYDROUS DIPHENYLCYCLOPROPENONE. VARIATIONS OF THE MOLECULAR GEOMETRY DUE TO HYDROGEN BONDING

1974 ◽  
Vol 3 (6) ◽  
pp. 639-642 ◽  
Author(s):  
Harumichi Tsukada ◽  
Hirotaka Shimanouchi ◽  
Yoshio Sasada
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Geometry ◽  
X Ray

scholarly journals Rational synthesis of an atomically precise carboncone under mild conditions

2019 ◽  
Vol 5 (8) ◽  
pp. eaaw0982 ◽  
Author(s):  
Zheng-Zhong Zhu ◽  
Zuo-Chang Chen ◽  
Yang-Rong Yao ◽  
Cun-Hao Cui ◽  
Shu-Hui Li ◽  
...  
Keyword(s):  
Apex Angle ◽  
Facile Synthesis ◽  
Reaction Conditions ◽  
X Ray ◽  
Carbon Allotropes ◽  
X Ray Crystallography ◽  
Mild Conditions ◽  
Research Opportunity ◽  
Insight Into ◽  
Structural Strain

Carboncones, a special family of all-carbon allotropes, are predicted to have unique properties that distinguish them from fullerenes, carbon nanotubes, and graphenes. Owing to the absence of methods to synthesize atomically well-defined carboncones, however, experimental insight into the nature of pure carboncones has been inaccessible. Herein, we describe a facile synthesis of an atomically well-defined carboncone[1,2] (C70H20) and its soluble penta-mesityl derivative. Identified by x-ray crystallography, the carbon skeleton is a carboncone with the largest possible apex angle. Much of the structural strain is overcome in the final step of converting the bowl-shaped precursor into the rigid carboncone under mild reaction conditions. This work provides a research opportunity for investigations of atomically precise single-layered carboncones having even higher cone walls and/or smaller apex angles.

The Molecular Geometry of Diastereoisomeric Bis[α-(9-anthryl)ethyl] Ethers

1985 ◽  
Vol 38 (9) ◽  
pp. 1417 ◽  
Author(s):  
H Becker ◽  
VA Patrick ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Least Squares ◽  
Dihedral Angle ◽  
Molecular Geometry ◽  
Dihedral Angles ◽  
Methyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
Meso Form ◽  
Aromatic Systems

The crystal structures of racemic bis [α-(9-anthryl)] ether and its meso form have been determined by single-crystal X-ray diffraction methods at 295 K, being refined by least squares to residuals of 0.053 and 0.041 for 1868 and 3568 independent 'observed' reflections respectively. Crystals of the racemate are orthorhombic, Pcab, a 23.07(1), b 19.85(2), c 10.241(8) Ǻ, Z 8. Crystals of the meso form are triclinic, Pī , a 19.032(12), b 14.207(11), c 9.451(8) Ǻ, α 79.46(6), β 89.68(6), γ 68.97(5)°, Z 4. In the racemate , the dihedral angle between the methyl groups along the ether bonds is 12°, and the short axes of the anthracene moieties lie at an angle of about 120°. In the meso compound, for the two molecules the dihedral angles between the methyl groups along the ether bonds are 90 and 93°, the angle between the two anthracene moieties is 90°, and the interplanar angles between the partly overlapping aromatic systems are 46 and 43°.

Carboxyl graphene reinforced melamine-based polyamide nanocomposites

2021 ◽  
pp. 089270572110514
Author(s):  
Himanshu V Madhad ◽  
Dilip V Vasava
Keyword(s):  
Electron Microscopy ◽  
Decomposition Temperature ◽  
Differential Scanning Calorimetric ◽  
X Ray Diffraction ◽  
One Pot ◽  
X Ray ◽  
Mild Conditions ◽  
Thermal Stability Of ◽  
Infrared Techniques ◽  
Scanning Electron

Over the years, various types of techniques have been used for the synthesis of nanocomposites. In this work, melamine-based polyamide (PA) was synthesized using a one-pot polycondensation method under mild conditions. carboxyl graphene (CG)/PA nanocomposites (CGMPA) were prepared by CG nanofiller loadings of 1, 3, and 5 wt.% via delamination/adsorption approach. The prepared CGMPA nanocomposites were characterized using different analyses, such as Fourier transform infrared techniques (FTIR), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), differential scanning calorimetric (DSC), and thermogravimetric analysis (TGA). The effects of the CG on the thermal properties of the CGMPA nanocomposites were significant. The results showed that the melting temperature (Tm) of neat PA and CGMPA were increased from 378°C to 393°C suggested better dispersion of CG in PA matrix. The decomposition temperature of PA was increased from 451°C to 463°C in CGMPA nanocomposites indicates the better thermal stability of PA matrix by addition of CG.

scholarly journals Novel synthesis of furancarboxylate derivatives via cyclization reactions of (E)-ethyl 3-aryl-2-cyanoacrylates and ethyl glycinate hydrochloride

2020 ◽  
pp. 174751982095959
Author(s):  
Naili Luo ◽  
Shan Wang ◽  
Zhenjie Su ◽  
Cunde Wang
Keyword(s):  
Synthetic Approach ◽  
Cyclization Reactions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Mild Conditions ◽  
Novel Synthesis ◽  
Substituted Furans

An efficient synthetic approach for the preparation of densely substituted furans starting from ( E)-ethyl 3-aryl-2-cyanoacrylates and ethyl glycinate hydrochloride mediated by 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of water is investigated. The reactions are carried out under mild conditions in N,N-dimethylformamide at 95 °C. The products are cleanly obtained in 50%–57% yields, resulting in an appealing alternative for accessing polysubstituted furan-2,4-dicarboxylates. The structure of a typical product, diethyl 5-amino-3-( p-tolyl)furan-2,4-dicarboxylate, is confirmed by X-ray crystallography.

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