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

Yu Xianghua, Tobin Jay Marks*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

106 Scopus citations

Abstract

A series of chiral organophosphine oxide/sulfide-substituted binaphtholate ligands have been prepared ({(R)-H 2 BINOL-[P(O)R 2 ] 2 } 2- , R = Ph, Et, t Bu, 3,5-xylyl, Bn, and OEt; {(R)-H 2 BINOL-[P(S)Ph 2 ] 2 } 2- ). The X-ray crystal structures of (R)-H 2 BINOL-[P(O)R 2 ] 2 (R = Ph, Et, and t Bu) 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(SiMe 3 ) 2 ] 3 (Ln = La, Nd, Sm, Y, Lu, and Sc) and the above binaphthols. The crystal structure of La 2 {(A)-BINOL-[P(O)Ph 2 ] 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)-Et 2 ] 2 }NdN(SiMe 3 ) 2 at room temperature. Lanthanide catalysts having varying organophosphine oxidesubstituted binaphtholate ligands exhibit differing enantioselectivity trends with decreasing Ln 3+ ionic radius, whereas Sc 3+ 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 (US)
Pages (from-to)365-376
Number of pages12
JournalOrganometallics
Volume26
Issue number2
DOIs
StatePublished - Jan 15 2007

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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