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Synthesis, applications and mechanistic investigations of C2 Symmetric Guanidinium salts

Allingham, M.T. and Bennett, E.L. and Davies, D.H. and Harper, P.M. and Howard-Jones, A. and Mehdar, Y.T.H. and Murphy, P.J. and Thomas, D.A. and Caulkett, P.W.R. and Potter, D. and Lam, C.M. and O'Donoghue, A.C. (2015) Synthesis, applications and mechanistic investigations of C2 Symmetric Guanidinium salts. Tetrahedron, 72 (4). pp. 496-503. DOI: 10.1016/j.tet.2015.11.058

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Abstract

A range of guanidinium catalysts was prepared in 6 or 7 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.

Item Type: Article
Subjects: Research Publications
Departments: College of Physical and Applied Sciences > School of Chemistry
Date Deposited: 25 Feb 2016 03:37
Last Modified: 25 Feb 2016 03:37
ISSN: 00404020
URI: http://e.bangor.ac.uk/id/eprint/6268
Identification Number: DOI: 10.1016/j.tet.2015.11.058
Publisher: Elsevier
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