Peter Haiss

University of Tuebingen, Tübingen, Baden-Württemberg, Germany

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Publications (8)24.95 Total impact

  • Peter Haiss, Klaus-Peter Zeller
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    ABSTRACT: As shown by deuterium labelling experiments, the deprotonation of the trimethylsulfonium ion (1) by the dimsyl anion (8) is accompanied by extensive hydrogen exchange. This cannot be explained by an acid-base equilibrium between the trimethylsulfonium ion (1) and the dimsyl anion (8) on one side and dimethylsulfonium methylide (2) and DMSO on the other side, because for thermodynamic reasons this process is irreversible due to the limited life-time of 2. Therefore, the isotopic exchange that accompanies the deprotonation is an indicator of a more complex deprotonation process. It is suggested that in a kinetically controlled reaction, a proton of 1 is transferred to the O-atom of 8 rather than to the carbanionic centre. This means that instead of DMSO, its tautomer, hydroxy-methylsulfonium methylide (10), is obtained in the deprotonation process. Similarly, in the acid-base interaction between DMSO and its conjugate base 8, the formation of the DMSO tautomer 10 is kinetically favoured. The intermediate 10 produced in this way transfers a DMSO-derived proton to 1 when it intervenes in the back reaction 10 + 2→8 + 1. An alternative mechanism based on methyl group exchange between 1 and 8 could be excluded by a (13)C-labelling experiment. The hydrogen exchange according to the suggested scenario is taking place in competition with the reaction of dimethylsulfonium methylide (2) with electrophilic substrates. This explains the different degrees of isotopic exchange when compounds of different electrophilicities are used to scavenge 2 from the deprotonation-hydrogen distribution equilibria.
    Organic & Biomolecular Chemistry 09/2011; 9(22):7748-54. DOI:10.1039/c1ob05889d · 3.49 Impact Factor
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    ABSTRACT: The complexes R(Ph)MeCOMg(Et2O)I [1, R = Me (a), Ph (b)] were obtained by the reaction of R(Ph)C=O with MeMgI in diethyl ether in good yields. Crystallisation of 1 from acetonitrile resulted in single crystals of di- and trinuclear complexes I2(μ-OCPhMe2)2Mg(MeCN)4 (2) and {2[I(MeCN)Mg(μ-OCPh2Me)2Mg(MeCN)I] (3) × [I(MeCN)Mg(μ-OCPh2Me)2Mg(μ-OCPh2Me)2Mg(MeCN)I] (4) × 2CH2Cl2} in which the metal centres are linked by alkoxy substituents. The thermal decomposition of the complexes 1 was studied by successive detection of the EI mass spectra of diethyl ether, the olefins 5, the tertiary alcohols 6, and the formal olefin dimers 7.
    Berichte der deutschen chemischen Gesellschaft 08/2011; 2011(22). DOI:10.1002/ejic.201100370
  • Peter Haiss, Klaus‐Peter Zeller
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    ABSTRACT: Nitrobenzenes carrying an ortho substituent are selectively methylated at the free ortho position by reaction with dimethylsulfonium methylide. The importance of the ortho substituent is demonstrated by the failure of the methylation of nitrobenzene and 3- and 4-nitroanisole. This is explained by the out-of-plane geometry of the nitro group in the ortho-substituted derivative, which enables a specific interaction between the ylide and the nitro group favourable for attack of the methylide C atom at the neighbouring free ortho position. As shown by appropriate deuterium-labelling studies, the addition is followed by an E1-like β-elimination with displacement of dimethyl sulfide and subsequent protonation of the elimination product.
    European Journal of Organic Chemistry 01/2011; 2011(2):295 - 301. DOI:10.1002/ejoc.201001091 · 3.15 Impact Factor
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    ABSTRACT: The product pattern found for the dimethyldioxirane-mediated oxidation of phenylethyne strongly depends on the reaction conditions. Dimethyldioxirane generated in situ from caroate (HSO(5)(-)) and acetone in acetonitrile-water furnishes phenylacetic acid as the main product. With solutions of dimethyldioxirane in acetone, mandelic acid and phenylacetic acid are mainly formed. The relative abundances of the two acids depend on the residual water present in the dimethyldioxirane-acetone solution. Application of thoroughly dried solutions of the reagent effects increased formation of mandelic acid. When phenylethyne is oxidized by dimethyldioxirane transferred into tetrachloromethane, to minimize traces of water even further, oligomeric mandelic acid is obtained. The results are rationalized by the initial formation of phenyloxirene, which is known to equilibrate with phenylformylcarbene and benzoylcarbene. Subsequent Wolff rearrangement produces intermediate phenylketene, which can be trapped by water as phenylacetic acid or suffer from further oxidation to the alpha-lactone of mandelic acid. The alpha-lactone can either react with water to yield mandelic acid or, under anhydrous conditions, to yield oligomeric mandelic acid. In addition to mandelic acid and phenylacetic acid phenylglyoxylic acid, benzoic acid and benzaldehyde are observed as reaction products. The formation of phenylglyoxylic acid by transfer of two oxygen atoms to the unrearranged carbon skeleton of phenylethyne followed by oxygen insertion into the aldehydic C-H bond of the intermediately formed phenylglyoxal is discussed. In a second pathway this acid is formed by partial oxidation of mandelic acid. Benzaldehyde and benzoic acid are explained as products of the oxidative degradation of the alpha-lactone by dimethyldioxirane. Under in situ conditions benzoic acid is also formed by caroate initiated oxidative decarboxylation of phenylglyoxylic acid and/or intermediate phenylglyoxal.
    Organic & Biomolecular Chemistry 07/2005; 3(12):2310-8. DOI:10.1039/b504296h · 3.49 Impact Factor
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    ABSTRACT: Crossover 13C NMR experiments between [13C]carbonate and [18O]carbonate in aqueous solution confirm the combined action of two oxygen-exchange modes. The isotopomeric carbon dioxides formed in the hydrolysis equilibrium of the labeled carbonate anions react with hydroxide with formation of hydrogencarbonate and with isotopomeric carbonate anions yielding the corresponding dicarbonate species, which, in the back reaction, form carbon dioxide and carbonate anions with distributed oxygen. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
    Berichte der deutschen chemischen Gesellschaft 01/2005; 2005(1):168 - 172. DOI:10.1002/ejic.200400445
  • Peter Haiss, Klaus-Peter Zeller
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    ABSTRACT: Ethyl 2-diazo-4,4,4-trifluoroacetoacetate (1a) and 3-diazo-1,1,1-trifluoro-2-oxopropane (1b) exhibit a deviating behavior in solution photolysis (hydrogen abstraction for 1a; Wolff rearrangement for 1b) [(a) F. Weygand, W. Schwenke and H. J. Bestmann, Angew. Chem., 1958, 70, 506; (b) F. Weygand, H. Dworschak, K. Koch and S. Konstas, Angew. Chem., 1961, 73, 409]. As shown by 13C-labelling of 1b this difference is not caused by rearrangement of the primarily formed alpha-oxocarbene to an isomeric alpha-oxocarbene presenting a hydrogen atom as a migrating substituent for the Wolff rearrangement. It is discussed that the singlet alpha-oxocarbene generated from 1a rapidly undergoes spin equilibration followed by hydrogen abstraction of the triplet alpha-oxocarbene. In contrast, due to a larger singlet-triplet splitting in the singlet alpha-oxocarbene generated from 1b, the intramolecular Wolff rearrangement on the singlet surface can efficiently compete with the singlet-triplet interconversion.
    Organic & Biomolecular Chemistry 08/2003; 1(14):2556-8. DOI:10.1039/B304002J · 3.49 Impact Factor
  • Peter Haiss, Klaus-Peter Zeller
    Angewandte Chemie International Edition 01/2003; 42(3):303-5. DOI:10.1002/anie.200390101 · 11.34 Impact Factor
  • Peter Haiss, Klaus-Peter Zeller
    Angewandte Chemie 01/2003; 115(3):315-318. DOI:10.1002/ange.200390069