- H-tetraoxaspirophosphoranes as possible intermediates in the phosphonylation by phosphorous acid / oxiranes
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The detailed 31P-NMR study of the mechanism of the ribozymomimetic phosphonylation with phosphorous acid / oxirane revealed consecutive formation of β-hydroxy H-phosphonate monoester, di-(β-hydroxyalkyl) H-phosphonate, alkylene H-phosphonate, β-hydroxyalkyl alkylene phosphite and the corresponding stereoelectronically stabilized pentacoordinated H-tetraoxaspirophosphorane. The equilibrium between the triphosphite and the spirophosphorane shifts towards the β-hydroxyalkyl alkylene phosphite at high temperatures. In the presence of alcohol and controlled amounts of water transesterification of the β-hydroxyalkyl alkylene phosphite to the corresponding alkyl alkylene phosphite, and hydrolysis to β-hydroxyalkyl alkyl H-phosphonate proceed at the elevated temperature. β-Hydroxyalkyl alkyl H-phosphonates are model compounds of the phosphodiester bond and undergo hydrolysis with a diol leaving in the presence of one equivalent of water.
- Tzokov, Svetomir B.,Vassilev, Nikolay G.,Momtcheva, Rositza T.,Kaneti, Jose,Petkov, Dimiter D.
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p. 187 - 196
(2007/10/03)
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- Syntheses und NMR-Spektren phosphororganischer Antioxidantien und verwandter Verbindungen
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The syntheses of various aliphatic, aromatic, sterically hindered, and cyclic organophosphorus compounds (phosphorous acid esters, esters chlorides and ester amides, hydrogen phosphites, phosphinates and phosphates) are reported, and general procedures for preparation are given.The compounds synthesized were investigated by means of 31P-, 1H- and 13C-n.m.r. spectroscopy, and the chemical shifts measured are listed.
- Koenig, T.,Habicher, W.D.,Haehner, U.,Pionteck, J.,Rueger, C.,Schwetlick, K.
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p. 333 - 349
(2007/10/02)
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- The Reaction Between Oximes and Tervalent Phosphorus Compounds: A Low-Temperature Radical Rearrangement Process
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Ketoximes react rapidly with X2PCl compounds where X = Ph, Me2N, EtO and X2 = OCH2CH2O at low temperatures (-60 to -80 deg C) in the presence of triethylamine to give a PIII intermediate 2, which rearranges by a unimolecular process to the corresponding N-phosphinylated imine 3.Free radicals, formed by capture of the initially produced phosphonyl radical, are detected by ESR spectroscopy, and evidence for a radical cage process is obtained from 31P CIDNP studies.Where X2 = OCH2CH2O, the PIII intermediate (2d, e) can be isolated, and the structure established from 13C NMR spectra.Kinetic measurements show compound 2e to rearrange (30 - 60 deg C) ca. 10 times more slowly than the open chain compound (X = OEt), and the negative activation entropy suggests that this particular system (2e) rearranges, in part, by a cyclic transition state.
- Hudson, Robert F.,Brown, Charles,Maron, A.
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p. 2560 - 2573
(2007/10/02)
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