Constrained geometry aminooxazolinate ligands giving chiral zirconium guanidinates; catalytic cyclohydroamination
Gott, Andrew L., Clarkson, Guy J., Deeth, Robert J., Hammond, Max L., Morton, Colin and Scott, Peter. (2008) Constrained geometry aminooxazolinate ligands giving chiral zirconium guanidinates; catalytic cyclohydroamination. Dalton Transactions (No.22). pp. 2983-2990. ISSN 1477-9226Full text not available from this repository.
Official URL: http://dx.doi.org/10.1039/b803831g
DFT calculations indicate that contrary to a prior report, N-heterocycle-augmented constrained geometry ligands e. g. Cp '-SiMe2-NR (Cp ' = Me4C5, R = 2-pyridine) should be capable of binding both atoms of the diazaallyl fragment at zirconium. This was confirmed by a molecular structure of a previously reported complex. Similar R = 2-oxazoline complexes were also shown to be feasible, although an additional N,O binding mode was accessible. The proligands HCp '-SiMe2-NHR (R = chiral non-racemic 2-oxazoline) were readily synthesised in high yield via base mediated reaction of 2-aminooxazolines and Cp '-SiMe2Cl. Subsequent reaction with Zr(NMe2)(4) gave, rather than the desired complexes, configurationally stable chiral-at-zirconum guanidinate/alkoxide chelate products; the aminooxazolinate units had undergone ring-opening and migratory insertion of -NMe2. Trends in the level diastereoselection follow the steric demand of the oxazoline substituent, with the larger groups (Bu-t, Pr-i) giving single diastereomers. The modest performance of these guanidinate compounds in enantioslective catalytic cyclohydroamination of aminoalkenes follows the expected trends for metal accessibility in a sigma-amido insertative mechanism.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry|
|Divisions:||Faculty of Science > Chemistry|
|Library of Congress Subject Headings (LCSH):||Amination, Ligands, Ligand binding (Biochemistry), Catalysis, Zirconium, Chirality|
|Journal or Publication Title:||Dalton Transactions|
|Publisher:||Royal Society of Chemistry|
|Number of Pages:||8|
|Page Range:||pp. 2983-2990|
|Access rights to Published version:||Restricted or Subscription Access|
|Funder:||Engineering and Physical Sciences Research Council (EPSRC)|
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