M.T. Allingham
Synthesis, applications and mechanistic investigations of C2 symmetric guanidinium salts
Allingham, M.T.; Bennett, E.L.; Davies, D.H.; Harper, P.M.; Howard-Jones, A.; Mehdar, Y.T.H.; Murphy, P.J.; Thomas, D.A.; Caulkett, P.W.R.; Potter, D.; Lam, C.M.; O’Donoghue, A.C.
Authors
E.L. Bennett
D.H. Davies
P.M. Harper
A. Howard-Jones
Y.T.H. Mehdar
P.J. Murphy
D.A. Thomas
P.W.R. Caulkett
D. Potter
C.M. Lam
Professor Ann O'Donoghue annmarie.odonoghue@durham.ac.uk
Professor
Abstract
A range of guanidinium catalysts was prepared in six or seven synthetic steps and applied to the phase transfer alkylation of a glycinate Schiff's base in 21–86% ee as well as the phase transfer epoxidation of some chalcones in 85–94% ee. Using a spectrophotometric method, pKa values in the range 13.2–13.9 in DMSO have been determined for some of the catalysts highlighting an increase in basicity relative to achiral tetramethylguanidine (pKa=13.0) and a mechanism involving the protonated guanidinium ion as a phase transfer catalyst is proposed. The use of two of the catalysts for the addition of nucleophiles in Michael addition reactions was investigated and both were found to be effective catalysts. A counterion effect was apparent in these reactions, but no enantioselectivity was observed.
Citation
Allingham, M., Bennett, E., Davies, D., Harper, P., Howard-Jones, A., Mehdar, Y., …O’Donoghue, A. (2016). Synthesis, applications and mechanistic investigations of C2 symmetric guanidinium salts. Tetrahedron, 72(4), 496-503. https://doi.org/10.1016/j.tet.2015.11.058
Journal Article Type | Article |
---|---|
Acceptance Date | Nov 24, 2015 |
Online Publication Date | Nov 30, 2015 |
Publication Date | Jan 28, 2016 |
Deposit Date | Feb 12, 2016 |
Publicly Available Date | Nov 30, 2016 |
Journal | Tetrahedron |
Print ISSN | 0040-4020 |
Publisher | Elsevier |
Peer Reviewed | Peer Reviewed |
Volume | 72 |
Issue | 4 |
Pages | 496-503 |
DOI | https://doi.org/10.1016/j.tet.2015.11.058 |
Keywords | Guanidine, Guanidinium ions, Phase transfer catalysis, Phase transfer alkylation, Phase transfer epoxidation, Michael addition. |
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http://creativecommons.org/licenses/by-nc-nd/4.0/
Copyright Statement
© 2015 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
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