Organophosphine oxide/sulfide-substituted lanthanide binaphtholate catalysts for enantioselective hydroamination/cyclization

Yu Xianghua, Tobin J. Marks

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106 Citations (Scopus)

Abstract

A series of chiral organophosphine oxide/sulfide-substituted binaphtholate ligands have been prepared ({(R)-H2BINOL-[P(O)R2] 2}2-, R = Ph, Et, tBu, 3,5-xylyl, Bn, and OEt; {(R)-H2BINOL-[P(S)Ph2]2}2-). The X-ray crystal structures of (R)-H2BINOL-[P(O)R2] 2 (R = Ph, Et, and tBu) evidence the varying binaphtholate dihedral angles and conformational flexibility possible for these ligands. Precatalysts for enantioselective intramolecular aminoalkene hydroamination/cyclization are conveniently generated in situ from the metal homoleptic dialkylamido precursors Ln[N(SiMe3)2] 3 (Ln = La, Nd, Sm, Y, Lu, and Sc) and the above binaphthols. The crystal structure of La2{(A)-BINOL-[P(O)Ph2] 2}3 reveals strong coordination of lanthanide ion by the phosphine oxide moieties. Enantioselectivities as high as 65% ee for the hydroamination/cyclization of 2,2-dimethylpent-4-enylamine are obtained with {(R)-BINOL-[P(O)-Et2]2}NdN(SiMe3)2 at room temperature. Lanthanide catalysts having varying organophosphine oxidesubstituted binaphtholate ligands exhibit differing enantioselectivity trends with decreasing Ln3+ ionic radius, whereas Sc3+ catalysts afford enantioselectivities with opposite product configurations. Kinetic studies reveal that the hydroamination rate is zero-order in [aminoalkene], consistent with the generally accepted mechanism for organolanthanide-catalyzed hydroamination/cyclization.

Original languageEnglish
Pages (from-to)365-376
Number of pages12
JournalOrganometallics
Volume26
Issue number2
DOIs
Publication statusPublished - Jan 15 2007

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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