TY - JOUR
T1 - Organophosphine oxide/sulfide-substituted lanthanide binaphtholate catalysts for enantioselective hydroamination/cyclization
AU - Xianghua, Yu
AU - Marks, Tobin Jay
PY - 2007/1/15
Y1 - 2007/1/15
N2 -
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.
AB -
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.
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U2 - 10.1021/om0607999
DO - 10.1021/om0607999
M3 - Article
AN - SCOPUS:33846570471
VL - 26
SP - 365
EP - 376
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 2
ER -