Stereoselective addition of diphenylphosphine to substituted diphenylethynes: synthetic, NMR and X-ray crystallographic studies

1998 ◽  
pp. 811-818 ◽  
Author(s):  
Jonathan L. Bookham ◽  
Darren M. Smithies ◽  
Anna Wright ◽  
Mark Thornton-Pett ◽  
William McFarlane
Keyword(s):  
X Ray ◽  
Stereoselective Addition

Synthesis With Chelated Imino Carboxylates: The Influence of Chelate Coligands on Reaction Pathways

1993 ◽  
Vol 46 (10) ◽  
pp. 1557 ◽  
Author(s):  
KJ Drok ◽  
JM Harrowfield ◽  
SJ Mcniven ◽  
AM Sargeson ◽  
BW Skelton ◽  
...  
Keyword(s):  
Ethyl Cyanoacetate ◽  
Reaction Pathways ◽  
Preliminary Evaluation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Stereoselective Addition ◽  
Equilibrium Control ◽  
Synthetic Utility ◽  
Structure Determinations ◽  
Complex Ion

Synthesis and X-ray crystallography have been used to explore the chemistry of chelates derived from the imines of pyruvic and phenylpyruvic acids held in a chiral environment on cobalt(III) as [Co(en)2(HNC(CH3)CO2)]2+ (en = ethane-1,2-diamine) and [Co(en)2(HNC(CH2C6H5)CO2)]2+. The latter complex was obtained by an especially facile dehydration of the corresponding β-phenylserine complex. Significant differences in both stereo- and regio-selectivity were detected in reactions of the two complexes, and, for the reaction of butenone with [Co(en)2(HNC(CH3)CO2)]2+, a pathway indetectable in previously studied reactions of the tetraammine analogue, and leading to a chelate of 4-methyl-5,6-dihydropyridine-2-carboxylate, was observed to be dominant. Kinetically determined stereospecificity was evident in the addition of ethyl cyanoacetate to [Co(en)2(HNC(CH3)CO2)]2+, whereas equilibrium control appears to exist in the stereoselective addition of nitromethane to both complexes. Crystal structure determinations on five new complexes have been used to establish these points and other important aspects of the chemical syntheses. A considerable number of new imino and amino acids can be derived through the reactions described, and the synthetic utility of both the tetraammine and bis ( ethanediamine ) complex ion systems in providing the 'free' organic products has been subjected to preliminary evaluation through the isolation of t- leucine , N-methyl-2-phenylglycine, 2-aminomethylalanine, and some vinylglycine derivatives.

Regio- And Stereoselective Addition Of Imides To Ethyl 3-Phenyl-2- Propynoate In The Presence Of Triphenylphosphine. Single Crystal X-Ray Structure Of Ethyl (Z)-2-(1,3-Dioxo-1,3,3A,4,7,7A-Hexahydro-2H-Isoindol- 2-Yl)-3-Phenyl-2-Propenoate

2007 ◽  
Vol 62 (6) ◽  
pp. 829-834 ◽  
Author(s):  
Amir Tofangchi Mahyaria ◽  
Nahid Shajari ◽  
Ali Reza Kazemizadeh ◽  
Katarzyna Ślepokura ◽  
Tadeusz Lis ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Structural Analysis ◽  
Single Crystal ◽  
Structure Determination ◽  
One Pot ◽  
X Ray ◽  
One Pot Synthesis ◽  
Stereoselective Addition ◽  
High Yields ◽  
C Nmr

A one-pot synthesis of sterically congested N-vinyl imides in fairly high yields by the reaction of ethyl 3-phenyl-2-propynoate, imides and triphenylphosphine is reported. The structures of these compounds were confirmed by IR, 1H, and 13C NMR spectroscopy, and by a single crystal X-ray structure determination. The structural analysis of the products indicated that the reaction is regioand stereoselective

Stereoselective addition of acetone to the C=N bond of [4.3.0] boron heterobicycles

2001 ◽  
Vol 79 (8) ◽  
pp. 1229-1237 ◽  
Author(s):  
Victor Barba ◽  
Damian Cuahutle ◽  
Rosa Santillan ◽  
Norberto Farfán
Keyword(s):  
Solid State ◽  
Schiff Bases ◽  
Boronic Acid ◽  
Boronic Acids ◽  
Tridentate Ligands ◽  
X Ray ◽  
Dimeric Structure ◽  
Stereoselective Addition ◽  
Phenyl Boronic Acid ◽  
Boron Complexes

The reaction of N-salicylidene-2-aminophenolate (SAP-H2) derivatives with phenyl boronic acid afforded five new boron bicyclic species in moderate yields, as confirmed by an X-ray study of the boron heterocycle derived from 2-amino-4-chlorophenol. The results also showed that the boron complexes derived from Schiff bases undergo an acetolysis reaction to give the corresponding dioxazaborocines containing all substituents on the same side also in good yields. The structure of one of the addition products was established by X-ray analysis showing that, in the solid state, it exists as a dimeric structure formed by hydrogen bonds.Key words: borocines, tridentate ligands, imines, boronic acids.

Space and Time Distribution of Hard X-Ray Emission in a Loop at the Beginning of a Flare

1994 ◽  
Vol 144 ◽  
pp. 275-277
Author(s):  
M. Karlický ◽  
J. C. Hénoux
Keyword(s):  
Time Distribution ◽  
Electron Bombardment ◽  
Spatial Evolution ◽  
Superthermal Electrons ◽  
Flare Loop ◽  
X Ray ◽  
Superthermal Electron ◽  
Flare Loops ◽  
Chromospheric Evaporation ◽  
Temporal And Spatial

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.

Some Problems in Understanding the Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 1-9
Author(s):  
A. H. Gabriel
Keyword(s):  
Solar Corona ◽  
Solar Atmosphere ◽  
Theoretical Modelling ◽  
Total System ◽  
Major Advance ◽  
X Ray ◽  
Proper Perspective ◽  
Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Iron K-Line Emission from X-Ray Binaries

1988 ◽  
Vol 102 ◽  
pp. 47-50
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
F. Nagase
Keyword(s):  
Accretion Disk ◽  
Radiative Recombination ◽  
Characteristic Temperature ◽  
Line Emission ◽  
Ionization Front ◽  
Continuum Radiation ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

Diagnostics of Gold Laser Plasmas

1988 ◽  
Vol 102 ◽  
pp. 357-360
Author(s):  
J.C. Gauthier ◽  
J.P. Geindre ◽  
P. Monier ◽  
C. Chenais-Popovics ◽  
N. Tragin ◽  
...  
Keyword(s):  
Experimental Results ◽  
Pure Gold ◽  
Electronic Temperature ◽  
X Ray ◽  
Laser Plasmas ◽  
Collisional Radiative Model ◽  
Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

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