Chemistry Reference
In-Depth Information
PhB(OH)
2
Ni(acac) (5 mol %),
L37
,
Dibal-H (16 mol %),
KOH, THF,
Δ
Ph
OAc
50% ee (81%)
Ph
PhB(OH)
2
+
Pr
OAc
Pr
Ph
Ni(acac) (5 mol %),
L37
,
Dibal-H (16 mol %),
KOH, THF,
Δ
Pr
13% ee (42%)
PhMgBr
Ni(acac) (5 mol %),
L37
,
KOH, THF,
Δ
Ph
84% ee (97%)
OAc
Ph
PhMgBr
Pr
OPh
+
Pr
Ph
Ni(acac) (5 mol %),
L37
,
KOH, THF,
Δ
Pr
33% ee (85%)
O
p
R
N
Fe
PPh
2
L37
Scheme 8B.47.
Nickel-catalyzed allylic alkylation using oxazolinylferrocenyl phosphines as ligands.
R
2
L
R
1
Ni
Nu
Figure 8B.18.
Nickel-catalyzed allylic alkylation using hard nucleophiles.
on the assumption that the reaction proceeds via a square planar Ni
2+
- allyl complex (Fig.
8B.18), and that a hard nucleophile is transferred via the Ni atom to the allyl ligand,
they proposed that monodentate ligands should be more suitable for hard nucleophiles
than chelating ligands, which should disturb the coordination of the nucleophile toward
the Ni.
Therefore, they compared a set of monodentate ferrophites
L38 - L39
and the fer-
rocenylphosphine
L39d
with the bidentate ligands (
R
) -
BINAP
(
L23a
) and (
R
,
pS
) -
JOSIPHOS
((
R
,
pS
) -
L40a
) (Fig. 8B.19 ). As nucleophile AlMe
3
was used in the reaction
with allylic substrates, containing different leaving groups (Table 8B.26). In contrast to
copper-catalyzed allylations, which provide the γ-substitution product in a clean S
N
2 ′
substitution [199], in the nickel-catalyzed version mixtures of the two regioisomers, α
