- The proline-catalyzed asymmetric amination of branched aldehydes
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An efficient access to configurationally stable α,β- disubstituted α-amino aldehydes, oxazolidinones, and α-amino acids has been presented. Starting from simple and easily available racemic aldehydes, the α-aminated products were obtained using azodicarboxylates as the nitrogen source in up to 86 % ee and moderate to excellent yield. These products could further be converted both into the corresponding α-amino alcohols and, depending on the residue of the azodicarboxylates and the reaction conditions, into the oxazolidinones. On the other hand, oxidation towards the carboxylic acid and cleavage of the hydrazide bond under mild conditions revealed the free α-alkylated phenylglycine derivative. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Baumann, Thomas,Vogt, Henning,Braese, Stefan
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p. 266 - 282
(2007/10/03)
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- Reactivity and selectivity in the oxidation of styrene derivatives, II studies on the oxidation of p-substituted α-methylstyrenes
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The liquid phase oxidation of p-substituted (Br-, Cl-, t-Bu-, MeO-, CF3-) α-methylstyrenes and of α,p-dimethoxystyrene with pure oxygen was investigated in chlorobenzene solution and in presence of cumene and of cumene hydroperoxide in the temperature range 65-125°C. The product yields were determined gaschromatographically. The differences of the activation energies of the epoxide formation and the parallel reactions amount to 19-48 kJ/mol. The epoxide selectivity increases with increasing temperature and concentration of olefine. The relative chain propagation constants kp (C=C) were determined by competitive oxidation with cumene. The kp(C=C) values of p-substituted α-methylstyrenes can be correlated by the Hammett equation with both σ and σ+ substituent constants.
- Suprun, Wladimir
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p. 231 - 237
(2007/10/03)
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