New chemo-enzymatic approaches for the synthesis of (R)- and (S)-bufuralol
作者:Botond Nagy、Norbert Dima、Csaba Paizs、Jürgen Brem、Florin Dan Irimie、Monica Ioana Toşa
DOI:10.1016/j.tetasy.2014.08.002
日期:2014.10
molecules. While the (S)-isomer with a higher β-blocking activity is recommended for hypertension treatment, the (R)-enantiomer can be used as marker of hepatic activity. In this paper two new alternative approaches are described for their chemo-enzymaticsynthesis, providing both highly enantiomerically enriched stereoisomers of the target molecule (ee 96–98%). One route is based on the baker’s yeast
Palladium catalysed aryl amination reactions in supercritical carbon dioxide
作者:Catherine J. Smith、Melanie W. S. Tsang、Andrew B. Holmes、Rick L. Danheiser、Jefferson W. Tester
DOI:10.1039/b509345g
日期:——
Palladiumcatalysed C-N bond formation in supercritical carbondioxide has been accomplished. Carbamic acid formation is avoided in part through the use of an N-silylamine as the coupling partner. Employing a catalyst system of Pd2dba3(1 mol%) and 2-dicyclohexylphosphino-2',4',6'-triisopropyl-1,1'-biphenyl (X-Phos)(2 mol%) enabled the catalytic amination of aryl bromides and chlorides with N-silylanilines
trimethylsilylated dicarbamic acid esters 1–9 and 10 were prepared. Their thermal decomposition was studied in n-alkanes as media. The reactions were monitored by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), respectively. Some N-silylated cyclic ureas 11–15 were also prepared from the corresponding esters 2–6 by thermolysis. The crystal structures of 2, 5 and 8 are also discussed
The reaction of trimethylsilyl N,N-dimethylcarbamate with the sterically hindered alcohol 2-methylbutan-2-ol has been studied kinetically. The reaction shows autocatalytic character, and an equation has been derived which satisfactorily describes the kinetic behaviour. A mechanism is suggested for the reaction.