Silaheterocyclen, XXIV. / Silaheterocycles, XXIV.

1993 ◽  
Vol 48 (3) ◽  
pp. 318-332 ◽  
Author(s):  
Norbert Auner ◽  
Armin W. Weingartner ◽  
Eberhardt Herdtweck
Keyword(s):  
Energy Levels ◽  
Cycloaddition Reaction ◽  
Product Distribution ◽  
Diels Alder ◽  
Frontier Molecular Orbitals ◽  
X Ray Diffraction ◽  
Insertion Reactions ◽  
Ene Reaction ◽  
X Ray ◽  
Cycloaddition Product

The 1-amino-2-neopentylsilenes 5-8 are formed in the reaction of LitBu with the aminovinylsilanes 1-4 in n-pentane (addition of LitBu to the vinylic double bond with subsequent 1,2-elimination of LiCl). The α-Li adducts initially formed are trapped by Me3SiOSO2CF3 to yield α-SiMe3-silanes. The silenes undergo insertion reactions into the Si—O bond of Me3SiOMe. In the absence of any trapping reagent dimerization occurs. One of the 1,3-disilacyclobutanes thus formed (15) could be examined by X-ray diffraction. Reacting with 1,3-butadienes the chlorosubstituted silenes 5 and 8 yield [2 + 2]-cycloaddition products. With 1,3-cyclohexadiene Diels-Alder adducts are also obtained, but with cyclopentadiene the [4+2] adducts are formed exclusively. Products of an ene-reaction are observed upon treatment of 2,5-norbornadiene with the silenes 5 and 8.The methylsubstituted silene 6 does not undergo any cycloaddition reaction at all, while from silene 7 only traces of the cycloadducts are produced. Both species mainly yield the dimers. The preference for the [2+2] reaction type, exhibited by the silenes 5 and 8, is due to their polarity. The almost complete absence or low yield of any cycloaddition products from 6 or 7 can be correlated with the energy levels of their frontier molecular orbitals. The distribution of the disilacyclobutanes and cycloaddition product isomers is explained by the characteristics of the stereospecifically Ε-configurated silenes. The product distribution can also be rationalized considering the ambiphilic nature of the system ViRR′SiCl/Li1Bu.

scholarly journals Anti-Mycobacterium tuberculosis Terpenoids from Resina Commiphora

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1475 ◽  
Author(s):  
Chuan-Zhi Zhu ◽  
Bin-Yuan Hu ◽  
Jia-Wang Liu ◽  
Yi Cai ◽  
Xin-Chun Chen ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Human Cancer ◽  
Cycloaddition Reaction ◽  
Diels Alder ◽  
Drug Resistant ◽  
X Ray Diffraction ◽  
Cellular Toxicity ◽  
X Ray ◽  
Human Cancer Cells ◽  
New Compounds

Four new compounds including two new sesquiterpenoid dimers, commiphoroids E (1) and F (2), a new triterpenoid (3), and a new sesquiterpenoid (4), along with three known terpenoids (5−7) were isolated from Resina Commiphora, whose structures were identified by NMR spectra, HRESIMS, and X-ray diffraction analysis. Compounds 1 and 2 both bear an O-bridge ring and feature a plausible [4 + 2] Diels–Alder cycloaddition reaction. Antimycobacterial activities show that all the tested compounds (200 μM) could inhibit the growth of both sensitive and clinically multi-drug resistant (MDR) isolated strains. In addition, cellular toxicity of the isolates against human cancer cells and THP-1 monocyte cells was examined.

A Chemoenzymatic Synthesis of the cis-Decalin Core Associated with the Novel Anti-Mitotic Agent Phomopsidin: Some Observations Concerning a High-Pressure-Promoted Diels–Alder Cycloaddition Reaction of (1S,2R)-3-Methyl-cis-1,2-dihydrocatechol and the Anionic Oxy–Cope Rearrangement of Compounds Derived from the Adduct

2004 ◽  
Vol 57 (7) ◽  
pp. 641 ◽  
Author(s):  
Martin G. Banwell ◽  
Alison J. Edwards ◽  
Malcolm D. McLeod ◽  
Scott G. Stewart
Keyword(s):  
Cycloaddition Reaction ◽  
Diels Alder ◽  
Chemoenzymatic Synthesis ◽  
Cope Rearrangement ◽  
The Novel ◽  
X Ray Diffraction ◽  
Enantiomerically Pure ◽  
X Ray ◽  
Wittig Rearrangements ◽  
Rearrangement Reaction

The enantiomerically pure and enzymatically derived cis-1,2-dihydrocatechol 2 engages in a diastereofacially selective Diels–Alder cycloaddition reaction with commercially available lactone 3 at 19 kbar to afford adduct 4, which is readily elaborated to the diene-ol 13. Treatment of this last compound with KH/18[crown]-6 resulted in successive anionic oxy-Cope and 1,2-Wittig rearrangements to afford acyloin 14 embodying the cis-decalin core associated with the natural product phomopsidin (1). Compound 16 also engages in an anionic oxy-Cope rearrangement reaction to give, depending on the molar equivalents of base used, either the cis-decalin 17 or the hexahydroindene 18. The structure of compound 18 has been established by single-crystal X-ray diffraction analysis.

Structural Study of an Unusual Diels-Alder Adduct

1992 ◽  
Vol 45 (12) ◽  
pp. 2089 ◽  
Author(s):  
EL Ghisalberti ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Diffraction Study ◽  
Structural Study ◽  
Spectroscopic Studies ◽  
Diels Alder ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Chemical Evidence ◽  
Alder Adduct

The structure of the compound obtained on heating the naturally occurring clerodane furanoditerpene (1) had been formulated as (2) on the basis of spectroscopic studies. A single-crystal X-ray diffraction study on the dihydro derivative of (2) has confirmed this and provides support for the stereochemistry previously assigned to (1) on the basis of chemical evidence.

New, Homochiral Synthons Obtained through Simple Manipulations of Enzymatically Derived 3-Halo-cis-1,2-dihydrocatechols

2015 ◽  
Vol 68 (10) ◽  
pp. 1467 ◽  
Author(s):  
Lorenzo V. White ◽  
Ping Lan ◽  
Brett D. Schwartz ◽  
Anthony C. Willis ◽  
Martin G. Banwell
Keyword(s):  
Single Crystal ◽  
Cycloaddition Reaction ◽  
Diels Alder ◽  
X Ray

The bromoepoxide 5a, which is obtained from the homochiral and enzymatically derived cis-1,2-dihydrocatechol 1a, is readily and efficiently transformed into either isomer 8a or the corresponding methoxymethyl-ether 2a. Though both of these products can be fully characterized, they are somewhat unstable, with the former being converted into the crystalline enone 3a on standing and the latter readily participating in a Diels–Alder cycloaddition reaction with the potent dienophile N-phenyl-1,2,4-triazoline-3,5-dione to give adduct 7a. The single-crystal X-ray structures of compounds 3a and 7a are reported. Using the related chemistry the chloro-analogue, 3b, of enone 3a can be obtained.

Nanostructured Co3O4 Oxide for Low Temperature Ethanol Oxidation

2014 ◽  
Vol 798-799 ◽  
pp. 205-210
Author(s):  
Jairo Alberto Gomez-Cuaspud ◽  
Martin Schmal
Keyword(s):  
Ethanol Oxidation ◽  
Physicochemical Characterization ◽  
Fluorescence Analysis ◽  
Product Distribution ◽  
X Ray Diffraction ◽  
Ethanol Oxidation Reaction ◽  
Reaction Conditions ◽  
X Ray ◽  
Temperature Programmed ◽  
Combustion Technique

We investigated the synthesis of nanosized Co3O4 oxide by the polymerization-combustion technique, with different concentrations (3, 12 and 25% w/w) in the ethanol oxidation reaction. Characterization was done by X-ray fluorescence analysis, X-ray diffraction, temperature programmed reduction, scanning and transmission electronic microscopy and CO and H2 chemisorption. Principal results from physicochemical characterization show that the concentration of the metal oxide influence the product distribution and selectivity under isothermal conditions at 420 °C showed the formation of intermediate etoxi-species and preferential dehydrogenation reaction on stream of material. Specific concentrations result in high conversions and H2 selectivity under present reaction conditions.

Synthesis and X-ray diffraction data of 2-ethyl-6-(pyridin-4-yl)-7H-indeno[2,1-c]quinoline

2013 ◽  
Vol 29 (1) ◽  
pp. 53-57
Author(s):  
H.A. Camargo ◽  
A. Sánchez ◽  
J.A. Henao ◽  
Arnold R. Romero Bohórquez ◽  
Vladimir V. Kouznetsov
Keyword(s):  
Elemental Sulfur ◽  
Cycloaddition Reaction ◽  
Unit Cell ◽  
Gas Chromatography Mass Spectrometry ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Monoclinic System ◽  
X Ray ◽  
Cell Parameters ◽  
Xrpd Pattern

The compound 2-ethyl-6-(pyridin-4-yl)-7H-indeno[2,1-c]quinoline (2) (chemical formula C23H22N2) was synthesized through the free-solvent oxidation reaction mediated by elemental sulfur from the corresponding 2-ethyl-6-(pyridin-4-yl)-5,6,6a,11b-tetrahidro-7H-indeno[2,1-c]quinoline (1), an adduct easily obtained, using the Lewis acid-promoted [4 + 2] cycloaddition reaction. Preliminary molecular characterization was performed by Fourier transform-infrared and gas chromatography-mass spectrometry. The X-ray powder diffraction (XRPD) pattern for the title compound was analyzed and found to be crystallized in monoclinic system, space groupP21/n(N° 14) with refined unit-cell parametersa = 20.795 (8) Å,b = 7.484 (2) Å,c = 10.787 (2) Å andß = 93.96° (2). The volume of the unit cell isV = 1674.8 (6) Å3.

TOWARD EFFICIENT ELECTRON-TRANSPORTING AND BLUE-EMITTING MATERIALS FOR ORGANIC LIGHT-EMITTING DIODES: STRUCTURE AND PHOTOLUMINESCENT PROPERTIES OF SILOLE DERIVATIVES

2005 ◽  
Vol 14 (04) ◽  
pp. 487-495 ◽  
Author(s):  
YOUNGJIN KANG ◽  
JUNGCHEOL PARK ◽  
JUN HEO ◽  
KI-MIN PARK ◽  
JUN-HWAN AHN ◽  
...  
Keyword(s):  
Reduction Potential ◽  
Energy Levels ◽  
Coupling Reaction ◽  
Organic Light Emitting Diodes ◽  
X Ray Diffraction ◽  
Light Emitting ◽  
X Ray ◽  
Cyclic Voltametry ◽  
Organic Light ◽  
Cross Coupling Reaction

The potential blue-emitting as well as electron-transporting materials, 2,5-bis(3,5-trifluoromethylphenyl)-1,1-dimethyl-3,4-diphenylsilole (silole = silacyclopentadiene) (1) and 2,5-bis(3,5-trifluoromethylphenyl)-1,1-diphenyl-3,4-diphenylsilole (2), were synthesized by the Pd-mediated cross coupling reaction of corresponding bis(pheny-lethynyl)silanes with 1-bromo-3,5-trifluoromethylbenzene via intramolecular reductive cyclization. The structure of 2 was established by single-crystal X-ray diffraction analysis. In crystal structure, the dihedral angle between the functionalized phenyl groups containing CF3 at 2,5-position and central silole ring is about 48.70(6)°, showing the diminution of effective conjugation. These compounds exhibited high thermal stability without degradation up to 200°C. The absorption and photoluminescent properties, and cyclic voltametry have been evaluated. Compounds 1 and 2 in thin films showed intense blue emissions at 464–473 nm, respectively, in photoluminescence (PL). In electrochemistry, the reduction potential of 1 and 2 were at -1.92 and -1.81 V, respectively. The presence of substituents at 2,5′ — and/or 1,1′ — positions of siloe ring affected the LUMO energy levels through σ*–π* conjugation.

Preparation, Characterization and Spectroscopy of Eu3+ in Gd2O3 Nanorods

2008 ◽  
Vol 8 (3) ◽  
pp. 1398-1403 ◽  
Author(s):  
Liqin Liu ◽  
En Ma ◽  
Renfu Li ◽  
Xueyuan Chen
Keyword(s):  
Electron Microscopy ◽  
Fluorescence Spectra ◽  
Filling Factor ◽  
Energy Levels ◽  
Diffraction Field ◽  
X Ray Diffraction ◽  
Excitation Spectra ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Eu3+:Gd2O3 nanorods were prepared by a hydrothermal method. X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Fourier transform-infrared spectroscopy were used to characterize the resulting samples. Emission and excitation spectra were studied using xenon excited spectroscopic experiments at 10 K. Energy transfer from Gd3+ to Eu3+, from the band gap of the host to Eu3+, and from Eu3+ (S6) to Eu3+ (C2) was observed. The energy levels of Eu3+ at the C2 site of cubic Gd2O3 were experimentally determined according to the fluorescence spectra at 10 K, and fit well with the theoretical values. The standard deviation for the optimal fit was 12.9 cm−1. The fluorescent lifetime of 5D0 (2.3 ms at 295 K) was unusually longer than that of the bulk counterparts (0.94 ms), indicating a small filling factor (0.55) for the nanorod volume. However the lifetime of 5D1 was much shorter than that of the bulk counterparts, 65 μs at 10 K, 37 μs at 295 K.

Contributions to the Chemistry of Boron, 204 [1] An Unusual [2+2]-Cycloaddition Reaction of Dicobalt Octacarbonyl

1990 ◽  
Vol 45 (6) ◽  
pp. 828-832 ◽  
Author(s):  
Sreelatha Channareddy ◽  
Gerald Linti ◽  
Heinrich Nöth
Keyword(s):  
Diffraction Analysis ◽  
Cycloaddition Reaction ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dicobalt Octacarbonyl

Dicobalt octacarbonyl reacts with (9-fluorenylidene)(2,2,6,6-tetramethylpiperidino)borane (1) at ambient conditions in an unexpected [2+2]-cycloaddition to yield an oxaboretane derivative (2). The structure of 2 has been determined by X-ray diffraction analysis. Similarities between the complex 2 and other oxaboretanes are discussed.

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