Skip to main content

Research Repository

Advanced Search

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.

Synthesis, applications and mechanistic investigations of C2 symmetric guanidinium salts Thumbnail


Authors

M.T. Allingham

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



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.

Files





You might also like



Downloadable Citations