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Dynamic kinetic resolution in the asymmetric synthesis of β-amino acids by organocatalytic reduction of enamines with trichlorosilane
journal contributionposted on 12.11.2013 by Andrei Malkov, Sigitas Stoncius, Kvetoslava Vrankova, Matthias Arndt, Pavel Kocovsky
Any type of content formally published in an academic journal, usually following a peer-review process.
A new methodology based on the organocatalytic asymmetric hydrosilylation of enamines that allows a direct access to a range of β and β -amino acid derivatives was presented. The results show a successful reduction of aromatic substrates, a sterically more hindered ortho-substituted derivatives, and the thiophenyl analogue exhibiting lower reactivity. Fast enamine-imine equilibration is crucial as imines are chiral but racemic, while α-alkyl β-amino acids can be accessed by the symmetrical Mannich reaction. The α-alkyl derivatives have relative and absolute configuration due to their reduction with LiAlH into a known amino alcohols. Predominant formation of the anti isomer in 3o is consistent with conformation of the imine intermediate in the catalytic reduction.
The authors thank the EPSRC for grant no. GR/S87294/01, the European Socrates- Erasmus Exchange Program for a fellowship to M.A., and the University of Glasgow for a fellowship to K.V.