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Constrained geometry aminooxazolinate ligands giving chiral zirconium guanidinates; catalytic cyclohydroamination
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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. doi:10.1039/b803831g
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Official URL: http://dx.doi.org/10.1039/b803831g
Abstract
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 | ||||
| ISSN: | 1477-9226 | ||||
| Official Date: | 2008 | ||||
| Dates: |
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| Number: | No.22 | ||||
| Number of Pages: | 8 | ||||
| Page Range: | pp. 2983-2990 | ||||
| DOI: | 10.1039/b803831g | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access | ||||
| Funder: | Engineering and Physical Sciences Research Council (EPSRC) |
Data sourced from Thomson Reuters' Web of Knowledge
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