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Me
Me
Me
Me
Me Me
O
N
Br
[RuCl
2
(C
6
H
6
)]
2
(2.5 mol%)
PPh
3
(10 mol%)
K
2
CO
3
,NMP,120°C
O
N
O
N
+
+
Ph
Ph
Ph
62%
(31:69)
1.2 equiv
Me
Me
Me
Me
Br
O
N
[RuCl
2
(C
6
H
6
)]
2
(2.5 mol%)
PPh
3
(10 mol%)
K
2
CO
3
,NMP,120°C
O
N
+
Ph
1.2 equiv
11%
Scheme 12.80
Substituent effect on the ortho-arylation of an oxazoline derivative.
[RuCl
2
(p-cymene)]
2
(2.5 mol%)
K
2
CO
3
,NMP,120°C
O
N
O
N
+
Ar-OTs
Me
Ph
Me
Me
Me
Me
Me
N
P
N
H
O
Me
Me
HASPO (10 mol%)
Me
Me
Scheme 12.81 Ortho-arylation of an oxazoline derivative using HASPO.
OH
O
N
O
N
[RuCl
2
(p-cymene)]
2
(2.5 mol%)
K
2
CO
3
, DMA, HASPO (10 mol%), TsCl
120 °C, 18 h
+
Me
Ph
Me
Scheme 12.82 Ortho-arylation of an oxazoline derivative with phenol partner.
The presence of substituents on the oxazoline ring at the 4-position dis-
favored the product formation owing to increased steric crowding, hindering
the coordination of the metal with the nitrogen (Scheme 12.80).
In the presence of a highly active heteroatom-assisted secondary phos-
phine oxide (HASPO) ligand, both aryl chlorides and tosylates reacted with
the aryloxazoline (Scheme 12.81).
116
Ackermann and Mulzer reported phenol as a coupling partner for the
arylation of oxazolines.
141
The eciency of the ligand was found to be
solvent dependent. In the presence of polar DMA (N,N-dimethylacetamide)
solvent, HASPO preligand enabled the arylation, whereas in apolar toluene,
MesCOOH ligand furnished the desired product with comparable yield.
Under both conditions, sulfonyl chloride additive needs to be added. The
reaction proceeds via the in situ activation of phenol to phenyl tosylate with
TsCl (Scheme 12.82).
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