Chiral diethylzinc complexes with diamine ligands: synthesis, crystal structure and enantioselective solvent-free alkylation
2005 (English)In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 690, no 16, 3846-3853 p.Article in journal (Refereed) Published
In search for conglomerates of stereochemically labile organometallic reagents, three new complexes between diethylzinc and diamine ligands have been synthesized and structurally characterized by single-crystal X-ray diffraction methods. Ligands include N,N,N',N'-tetraethylethylenediamine (teeda), N-isopropyl-N,N',N'-trimethylethylenediamine (itmeda), and (-)-sparteine (spa). Diethylzinc forms monomeric complexes, exhibiting a distorted tetrahedral coordination geometry around zinc in all three complexes, viz. [ZnEt(2)(teeda)] (1), [ZnEt(2)(itmeda)] (2), and [ZnEt(2)(spa)] (3). Both 1 and 2 are stereochemically labile and exhibit chiral complexes, displaying different types of conformational chirality, but they form racemic crystals. By using the chiral crystals of 3 in a nucleophilic addition to benzaldehyde in the absence of solvent at low temperature, an increase in ee from approximately 8 to 10% was obtained (compared to the same reaction in solution). It thus seems feasible, not only to retain the enantioselectivity obtained in solution, but perhaps even to increase the ee by using solventless reactions.
Place, publisher, year, edition, pages
2005. Vol. 690, no 16, 3846-3853 p.
conglomerate, diethylzinc, N-chirogenic, solid-state reaction, solvent-free reaction
IdentifiersURN: urn:nbn:se:kth:diva-38298DOI: 10.1016/j.jorganchem.2005.05.015ISI: 000231945800027ScopusID: 2-s2.0-23844543394OAI: oai:DiVA.org:kth-38298DiVA: diva2:436648
QC 201108242011-08-242011-08-242011-08-24Bibliographically approved