Evidence for the structure, and for a non-chair conformation in ring F of two isomeric N-formylsolasodines

1983 ◽  
Vol 36 (2) ◽  
pp. 325 ◽  
Author(s):  
W Gaffield ◽  
M Benson ◽  
WF Haddon ◽  
RE Lundin
Keyword(s):  
Double Bond ◽  
Mass Spectra ◽  
Elevated Temperatures ◽  
Chair Conformation ◽  
Restricted Rotation ◽  
Nitrogen Inversion

Formylation of solasodine results in the formation of two different 3,N-diformylsolasodines whose isomerism is due to a difference in stereochemistry at C22 rather than restricted rotation about the C=N partial double bond of the amide or nitrogen inversion as previously proposed. Mass spectra, 1H and I3C n.m.r. spectra have shown the isomers to possess 22R,25R (major) and 22S,25R (minor) stereochemistry. The 22S,25R isomer is thermodynamically preferred at elevated temperatures while the 22R,25R isomer is kinetically favoured upon recyclization of the ring-F opened intermediate which forms upon heating of either isomer. A non-chair ring-F conformation is proposed for each isomer on the basis of 13C and 1H n.m.r. spectra.

Zur Cycloaddition von Azidoameisensäuremethylester an die Metall-Carben-Doppelbindung in η2-Thiocarbenkomplexen des Molybdäns und Wolframs / Cycloaddition of Azidoformic Acid Methylester to the Metal Carbon Double Bond of η2-Thiocarbene Complexes of Molybdenum and Tungsten

1993 ◽  
Vol 48 (11) ◽  
pp. 1481-1487
Author(s):  
Fritz R. Kreißl ◽  
Wolfgang Schutt ◽  
Josef Ostermeier ◽  
Claudia M. Stegmair ◽  
Waltraud Ullrich ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Mass Spectra ◽  
Space Group ◽  
Carbon Double Bond ◽  
Bicyclic System ◽  
And Tungsten

Cationic η2-thiocarbene complexes of molybdenum and tungsten [Cp(CO)PMe3[BF4] (R = Me, Ph, Tol) add N3COOMe to the electron rich metal carbon double bond to yield the corresponding bicyclic system. The products have been characterized by 1H, 13C, 31P NMR, IR and mass spectra. The crystal structure of 4b has been determined: space group P21/n with a = 1749.9(7), b = 827.9(1), c = 1846.8(7) pm and Z = 4.

scholarly journals Feldionen-Massenspektren organischer Moleküle IV. Olefine

1965 ◽  
Vol 20 (10) ◽  
pp. 1335-1344
Author(s):  
H. D. Beckey ◽  
P. Schulze
Keyword(s):  
Double Bond ◽  
Mass Spectra ◽  
Stable Configuration ◽  
Allyl Radical ◽  
Field Dissociation

The field ion mass spectra of the olefins are discussed. It is shown that the double bond and the bond next to it are very stable against field dissociation. The fragment patterns of all olefins show some features due to the stable configuration of the allyl radical or the allyl ion respectively. This is verified by some energetic calculations, by which the spectra of some olefins are explained, too. The stabilities of paraffins and olefins against field dissociation are compared.

scholarly journals Crystal structure of (9S,10S)-10-ethoxy-9-hydroxy-6,6,9-trimethyl-3-pentyl-7,8,9,10-tetrahydro-6H-benzo[c]chromen-1-yl 4-methylbenzenesulfonate

2015 ◽  
Vol 71 (12) ◽  
pp. o1082-o1083 ◽  
Author(s):  
Waseem Gul ◽  
Ahmed Galal ◽  
Mahmoud A. ElSohly ◽  
Paulo Carvalho
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Hydrogen Bonds ◽  
Chair Conformation ◽  
Heterocyclic Ring ◽  
Helical Chain ◽  
Aromatic Rings ◽  
Compound C ◽  
Cyclohexene Ring ◽  
Methylene Group

In the structure of the title compound, C30H40O6S, the cyclohexene and heterocyclic rings are linked by a double bond. The cyclohexene ring has a half-chair conformation (the methylene group adjacent to the hydroxy substituent lies above the remaining atoms) and the hydroxy and ethoxy groups have equatorial and bisectional dispositions, respectively. The heterocyclic ring has an envelope conformation (with the CMe2C atom being the flap). The dihedral angle between the aromatic rings is 53.88 (10)°. A long intramolecular C—H...S interaction is noted. In the molecular packing, hydroxy-O—H...O(sulfonate) hydrogen bonds lead to a helical chain along [010]. Connections between chains are of the type methyl-C—H...O(sulfonate) and lead to supramolecular layers that lie parallel to (001). The studied crystal was an inversion twin.

scholarly journals (2S,4S)-2-[(S,E)-2-Bromo-1-nitromethyl-3-phenylallyl]-4-methylcyclohexanone

2012 ◽  
Vol 68 (4) ◽  
pp. o1253-o1253
Author(s):  
Long Zhao ◽  
Chao Wu ◽  
Wen-Zeng Weng ◽  
Chu-Xia Yan ◽  
Ai-Bao Xia
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Chair Conformation ◽  
Cyclohexane Ring ◽  
Chiral Centers

The crystal structure of the title compoud, C17H20BrNO3, contains three chiral centers, which all exhibit anSconfiguration. The C=C double bond has anEconformation. The cyclohexane ring is in a chair conformation. In the crystal, molecules are linked by weak N—O...Br interactions [O...Br = 3.136 (4) Å].

Anhydrobetulin and its derivatives

1991 ◽  
Vol 56 (4) ◽  
pp. 886-904 ◽  
Author(s):  
Alois Vystrčil ◽  
Václav Křeček ◽  
Jiří Protiva ◽  
Miloš Buděšínský
Keyword(s):  
Double Bond ◽  
Alkaline Medium ◽  
Sodium Borohydride ◽  
Mass Spectra ◽  
Nmr Spectra ◽  
Cotton Effect ◽  
Addition Reactions ◽  
Chemical Transformations ◽  
C Nmr ◽  
Reduction Of Ketones

The structure of anhydrobetulin II and its derivatives I, III and IV has been solved using 1H and 13C NMR spectra, mass spectra and chemical transformations. It has been proven that in addition reactions the trisubstituted double bond is attacked selectively from the α-side under formation of D/E cis-annelated derivatives VIII, X and XI. The 22-oxo derivative XIII exhibits an anomalous Cotton effect and, in contrast to its saturated analogue XXVII,it is not epimerized in alkaline medium. Trinordiketone XXI easily epimerizes to a mixture in which the 17βH-epimer XXIb predominates, trinorketone XXIV is stable only if the annelation of rings D and E is trans. These differences are explained in terms of steric interactions of substituents in position 19. The steric course of reduction of ketones XIII and XXIV with sodium borohydride is described.

Nucleophilic Attack on the Carbon - Nitrogen Double Bond Leading to Tetrahedral Intermediates with Conformationally Restricted Stereochemistry

2008 ◽  
Vol 61 (11) ◽  
pp. 888 ◽  
Author(s):  
James E. Johnson ◽  
Lei Lu ◽  
Yi Li ◽  
Mei Hou ◽  
Jeffrey E. Rowe
Keyword(s):  
Double Bond ◽  
Chloride Ion ◽  
Chair Conformation ◽  
Nucleophilic Attack ◽  
Boat Conformation ◽  
Conformationally Restricted ◽  
Ion Substitution ◽  
Rate Ratios ◽  
Nitrogen Double Bond ◽  
Tetrahedral Intermediates

Methoxide ion substitution on 4-chloro-1H-2,3-benzoxazine 4 has been investigated. The rates of cyclization have been measured for (Z)- and (E)-O-(2-hydroxyethyl)benzohydroximoyl halides (PhC(X)=NOCH2CH2OH; X = Cl or Br) using potassium t-butoxide to generate alkoxide ions from the alcohols. The element effect for the Z and E isomers are kZBr/kZCl = 3.08 and kEBr/kECl = 2.38. The Z-to-E rate ratios are 0.25 (chlorides) and 0.33 (bromides). These reactions are proceeding by rate-determining nucleophilic attack by the alkoxide ion on the carbon–nitrogen double bond (AN# + DN). The restricted stereochemistry of the tetrahedral intermediates suggests that the E-hydroximoyl bromide and chloride may be undergoing unassisted ionization to form a zwitterionic intermediate that leads to product. Alternatively, the chair conformation of the tetrahedral intermediate may be undergoing a ring flip to a boat conformation in which there are antiperiplanar electron pairs that assist in the ionization of the bromide or chloride ion.

scholarly journals Mass spectra of dodecadienic compounds with a conjugated double bond, lepidopterous sex pheromones.

1985 ◽  
Vol 49 (2) ◽  
pp. 413-421 ◽  
Author(s):  
Tetsu ANDO ◽  
Yoshio KATAGIRI ◽  
Masaaki UCHIYAMA
Keyword(s):  
Double Bond ◽  
Mass Spectra ◽  
Sex Pheromones
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