Synlett 2003(1): 0022-0028
DOI: 10.1055/s-2003-36221
LETTER
© Georg Thieme Verlag Stuttgart · New York

1,2-Aminothioethers Derived from Ephedrine and Pseudoephedrine: Heterobidentate Ligands for the Palladium-Catalysed Asymmetric Allylic Substitution Reaction

Philip C. Bulman Page*, Harry Heaney, Serge Reignier, Gerasimos A. Rassias
Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, England
Fax: +44(1509)223926; e-Mail: p.c.b.page@lboro.ac.uk;
Further Information

Publication History

Received 25 October 2002
Publication Date:
18 December 2002 (online)

Abstract

Heterobidentate sulfide-tertiary amine ligands incorporating 1,2-aminothioethers derived from ephedrine and pseudoephedrine have been prepared and used successfully in the palladium-catalysed asymmetric allylic substitution reaction, giving ees of up to 89%. The stereoelectronic effects operating in the reactions are discussed.

36

In these transition state models we have assumed the effect of the sulfur tert-butyl group to be nearly neutral. We believe this to be a reasonable asumption because the S-tert-butyl group would be expected to experience interactions with both the ligand phenyl group and the N-tert-butyl group. It is possible that the sulfur may have considerable sp2 character as a result of these interactions; furthermore the S-tert-butyl group would be expected to exert less steric influence over the ligand than does the N-tert-butyl group as a carbon-sulfur bond is normally considerably longer than is a carbon-nitrogen bond.