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1997 (1)
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1Author    Rupert Herrmann, Helmut SchwarzRequires cookie*
 Title    Mechanisms of Electron Impact Induced Elimination of Methanol from ortho-and para-Substituted Benzoic Acid Methyl Ester  
 Abstract    Using deuterium labelled compounds the mechanisms of methyl as well as methanol elimination from the title compounds have been established. It can be shown that in the case of 4-methoxy-methyl benzoic acid methyl ester the unusual methanol elimination from the [M-methyl]+ ion probably proceeds via the formation of a jr-complex and a ring expansion reaction. In addition to this novel fragmentation some oriAo-effects and other fragmentation reactions useful for an analytical identification of the ortho/para-isomers by means of mass spectrometry are discussed. 
  Reference    (Z. Naturforsch. 31b, 870—875 [1976]; eingegangen am 19. Dezember 1975) 
  Published    1976 
  Keywords    ortho-Effect, Hydrogen Scrambling, Ring Expansion, Rearrangement 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-0870.pdf 
 Identifier    ZNB-1976-31b-0870 
 Volume    31 
2Author    Uwe Klingebiel, Lutz SkodaRequires cookie*
 Title    Fluoroboryl-and Fluoroboranediyl-Cyclosilazanes  
 Abstract    Hexamethylcyclotrisilazanes and their lithium salts react with F2BN(SiMe3)2 to give the corres­ ponding mono-, bis-, and tris(fluoroboryl)cyclotrisilazanes. Di-fluoroboryl-substituted rings are obtained in the reaction of l,3-bis(silyl)-and 1-boryl-cyclotrisilazanes with BF3-etherate. A com­ pound consisting of two cyclodisilazanes connected by a (SiNBNSi)-bridge is formed in the reaction of lithiated bis(silyl)cyclotrisilazane with BF3-etherate. Ring coupling of two six mem-bered rings occurs in the reaction of lithiated cyclotrisilazane with 1-difluoroboryl-cyclotrisilazane and in the reaction of lithiated bis(fluoroboryl)cyclotrisilazane with BF3-etherate in a molar ratio 2:1. Ring expansion takes place in the reaction of the lithium salt of a four membered SiN-ring with F2BN(SiMe3)2. Substitution occurs in the same reaction with F3SiN(SiMe3)2. 
  Reference    Z. Naturforsch. 40b, 913—918 (1985); eingegangen am 16. März 1985 
  Published    1985 
  Keywords    Cyclosilazanes, Fluoroboranes, Boryl Substitution, Ring Coupling, Ring Expansion 
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 TEI-XML for    default:Reihe_B/40/ZNB-1985-40b-0913.pdf 
 Identifier    ZNB-1985-40b-0913 
 Volume    40 
3Author    Z. NaturforschRequires cookie*
 Title    Ringerweiterungs-und -Verengungsreaktionen bei BN-Vier-und -Sechsringen  
 Abstract    Expansion and C o n tractio n R eactions w ith BN F our-and Six-M em bered Rings Peter Paetzold3 *, J u tta K iesgena, K arl K ra h éa, H ans-U lrich M eiera und R oland Boeseb By the addition o f im inoboranes R B = N R ' (l a -d) to the corresponding diazadiboretidines (R B N R ')2 (2 a -d), a ring expansion is observed, borazines (R B N R ')3 (3 a -d) being formed. The particular im inoborane iP rB =N /P r (la) can be added to the diazadiboretidines 2 c -g to give borazines B3N 3R2R'2/Pr2 with an unsymmetrical set o f ligands. From P hB =N rB u (lj) and (PhBNzBu), (2j), the Dewar borazine 3j' is formed, which crystallizes in the space group P 2,lc. The diazadiboretidines 2 b -i , the borazines 3 b -d ,f , and the Dewar borazine 3e' are split into the corresponding iminoboranes R B =N rB u at 5 0 0 -6 0 0 °C in the gas phase. The molten bo­ razines 3 b —d ,f and Dewar borazines 3e', j' are contracted to the corresponding diazadiboreti­ dines 2 b -f , j at 1 6 0 -3 2 0 °C. [Ligands R/R': zPr/zPr (a), Me/zBu (b), Et//Bu (c), Pr/?Bu (d), zPr/ ?Bu (e), Bu/rBu (f), /Bu/zBu (g), /Bu/rBu (h), zBu(M e3Si)N/zBu (i), Ph//Bu (j).] 
  Reference    Z. Naturforsch. 46b, 853—8 (1991); eingegangen am 26. N ovem ber 1990 
  Published    1991 
  Keywords    Iminoboranes, Diazadiboretidines, Borazines, Ring Expansion, Ring Contraction 
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 TEI-XML for    default:Reihe_B/46/ZNB-1991-46b-0853.pdf 
 Identifier    ZNB-1991-46b-0853 
 Volume    46 
4Author    Thom As Häusler, W. Illiam, S. SheldrickRequires cookie*
 Title    Metal-Mediated Assembly of Hexameric Ethylcycloarsoxane (C2H5AsO)6 in Mono-and Dinuclear Complexes with Tetrahedral and Octahedral Coordination Spheres  
 Abstract    A metal-assisted ring expansion from the preferred solution species (EtAsO),,, n = 3,4, to the hexameric ligand (EtAsO)6 is observed for the reactions of [ReBr(CO)5], [RuCLCPh^P)?], RhCfv3 H2 0 and [C^CCF.^SO.OaCCftHft)] with ethylcycloarsoxane. Whereas two metal frag­ ments are facially coordinated by the upper and lower three As atoms of a flattened AsftOö cuboctahedron in both [{ReBr(CO)2} 2 {M-[cyc/o-(EtAsO)6]}] (1) and [Cu2{n-[cyclo-(EtAs0)6]}(Me2PhP)2](CF3S03)2 (4), potential ring strain restricts the reaction with the other compounds to the formation of mononuclear complexes [RuCl2{cvc/o-(EtAsO)6}(Ph3P)] (2) 
  Reference    Z. Naturforsch. 52b, 679—686 (1997); received March 6 1997 
  Published    1997 
  Keywords    Ethylcycloarsoxane, Transition Metal Complexes, Metal-Mediation, Ring Expansion 
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 TEI-XML for    default:Reihe_B/52/ZNB-1997-52b-0679.pdf 
 Identifier    ZNB-1997-52b-0679 
 Volume    52 
5Author    Rupert Herrmann, Helmut SchwarzRequires cookie*
 Title    On the Mechanism of Substituent Interaction During bhe Electron Impact Induced Ether Cleavage from para-Substituted Methoxymethvl Benzenes  
 Abstract    The unusual methyl elimination from para-substituted methoxy-methyl benzenes has been elucidated. It can be shown that two entirely different mechanisms contribute to the reaction: i) intramolecular hydrogen transfer onto the benzene ring (7r-complex formation) and ii) substituent migration via ring expansion. Alternative mechanisms as for instance transanular protonation of the ester function or substituent migration via valence bond isomers are not involved in the formation of the [M-methyl]+-ions. 
  Reference    (Z. Naturforsch. 31b, 1667—1672 [1976]; eingegangen am 24. September 1976) 
  Published    1976 
  Keywords    Mass Spectrometry, Intramolecular Protonation, t-Complex, Rearrangement, Ring Expansion 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1667.pdf 
 Identifier    ZNB-1976-31b-1667 
 Volume    31