Synthesis, applications and mechanistic investigations of C2 Symmetric Guanidinium salts

M.T. Allingham; E.L. Bennett; Deiniol Davies; P.M. Harper; A.G. Howard-Jones; Y.T. Mehdar; P.J. Murphy; Dafydd Thomas; P.W. Caulkett; D. Potter; C.M. Lam; A.C. O'Donoghue

doi:10.1016/j.tet.2015.11.058

Synthesis, applications and mechanistic investigations of C2 Symmetric Guanidinium salts

M.T. Allingham, E.L. Bennett, Deiniol Davies, P.M. Harper, A.G. Howard-Jones, Y.T. Mehdar, P.J. Murphy, Dafydd Thomas, P.W. Caulkett, D. Potter, C.M. Lam, A.C. O'Donoghue

Knowledge Economy Skill; Menai Organics; Astra Zeneca; Leonardo Da Vinci Programme

Research output: Contribution to journal › Article › peer-review

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.

Original language	English
Pages (from-to)	496-503
Journal	Tetrahedron
Volume	72
Issue number	4
Early online date	30 Nov 2015
DOIs	https://doi.org/10.1016/j.tet.2015.11.058
Publication status	Published - 28 Jan 2016

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title = "Synthesis, applications and mechanistic investigations of C2 Symmetric Guanidinium salts",

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{\textquoteright}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.",

author = "M.T. Allingham and E.L. Bennett and Deiniol Davies and P.M. Harper and A.G. Howard-Jones and Y.T. Mehdar and P.J. Murphy and Dafydd Thomas and P.W. Caulkett and D. Potter and C.M. Lam and A.C. O'Donoghue",

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doi = "10.1016/j.tet.2015.11.058",

language = "English",

volume = "72",

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journal = "Tetrahedron",

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TY - JOUR

T1 - Synthesis, applications and mechanistic investigations of C2 Symmetric Guanidinium salts

AU - Allingham, M.T.

AU - Bennett, E.L.

AU - Davies, Deiniol

AU - Harper, P.M.

AU - Howard-Jones, A.G.

AU - Mehdar, Y.T.

AU - Murphy, P.J.

AU - Thomas, Dafydd

AU - Caulkett, P.W.

AU - Potter, D.

AU - Lam, C.M.

AU - O'Donoghue, A.C.

PY - 2016/1/28

Y1 - 2016/1/28

N2 - 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.

AB - 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.

U2 - 10.1016/j.tet.2015.11.058

DO - 10.1016/j.tet.2015.11.058

M3 - Article

SN - 0040-4020

VL - 72

SP - 496

EP - 503

JO - Tetrahedron

JF - Tetrahedron

IS - 4

ER -

Synthesis, applications and mechanistic investigations of C2 Symmetric Guanidinium salts

Abstract

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