910032-64-3Relevant academic research and scientific papers
Elucidating the mechanism of the asymmetric aza-Michael reaction
Phua, Pim Huat,Mathew, Suju P.,White, Andrew J. P.,De Vries, Johannes G.,Blackmond, Donna G.,Hii, King Kuok
, p. 4602 - 4613 (2008/02/09)
The mechanism of the palladium-catalysed asymmetric aza-Michael addition of aniline to α,β-unsaturated N-imide was examined from several aspects using a combination of techniques, including X-ray crystallography, mass spectrometry, NMR, UV/Vis spectroscopy, and kinetic studies. The binding of aniline to the dicationic palladium(II) metal centre was found to occur in two consecutive steps: The binding of the first aniline is fast and reversible, whereas the binding of the second aniline is slower and irreversible. This occurs in competition with the binding of the N-imide, which forms a planar six-membered chelate ring with the metal centre; coordinating through the 1,3-dicarbonyl moiety. Isotopic labelling revealed that the addition of N-H occurs in a highly stereoselective manner, allowing the synthesis of optically active β2- and β2.3-amino acid derivatives. The stereochemistry of the addition is postulated to be syn. In situ kinetic studies provided evidence for product inhibition. The binding of the N-imide to the catalyst was found to be the rate-limiting step. Aniline was found to be an inhibitor of the pre-catalyst. The study culminated in the design of a new reaction protocol. By maintaining a low concentration of the aniline substrate during the course of the reaction, significant enhancement of yield and enantioselectivity can be achieved.
Enabling ligand screening for palladium-catalysed enantioselective aza-Michael addition reactions
Phua, Pim Huat,White, Andrew J. P.,De Vries, Johannes G.,Hii, King Kuok
, p. 587 - 592 (2007/10/03)
The bis(trifluoromethanesulfonate)palladium(II) dihydrate complex, Pd(OTf)2·2 H2O (1), is an active palladium(II) precursor for the generation of dicationic palladium(II) catalysts. Parallel ligand screening is enabled for the first
Palladium-catalysed enantioselective conjugate addition of aromatic amines to α,β-unsaturated N-imides. Effect of the chelating moiety
Pim, Huat Phua,De Vries, Johannes G.,King, Kuok Hii
, p. 1775 - 1780 (2007/10/03)
Palladium-catalysed enantioselective additions of aromatic amines to α,β-unsaturated N-imides 4-6 are reported. The N-substituent of the Michael acceptor appears to have an unusual modulating effect on the amine activity. The effects of introducing differ
