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30 mol % NiCl
2
O
90 mol %
O
S
ArI
+
RSH
Ar
R
Zn, pyridine, CH
3
OH
Ar
R
Yield (%)
p
-CH
3
OC
6
H
4
C
6
H
5
70
p
-CH
3
OC
6
H
4
p
-ClC
6
H
4
67
p
-CH
3
OC
6
H
4
2,4-(CH
3
)
2
C
6
H
3
55
p
-CH
3
OC
6
H
4
HO(CH
2
)
5
81
p
-CH
3
OC
6
H
4
TBSO(CH
2
)
5
58
p
-CH
3
OC
6
H
4
PhthN(CH
2
)
3
55
Scheme 6.23
50 mol % NiCl
2
O
1.5 equiv
I
SH
S
O
Zn, pyridine, CH
3
OH
N
O
N
O
88%
CH
3
CH
3
50 mol % NiCl
2
I
S
SAc
60 mol %
N
N
N
CH
3
N
CH
3
Zn, pyridine, CH
3
OH
66%
Scheme 6.24
loading is high in intramolecular reactions with b-thioketones or with
thioacetates, these reactions provide structurally interesting thiazinones and
thiolactones in good yields.
6.6.3 Rhodium-Catalyzed Formation of Diaryl or Alkyl Aryl
Thioethers
The use of a rhodium hydride complex with dppBZ [1,2-bis(diphenylphos-
phino)benzene] catalyzes the cross-coupling between substituted aromatic
fluorides and diaryl sulfides (Scheme 6.25).
85
Although the aromatic fluoride
partners required strongly electron-withdrawing groups, the ability to employ
aromatic fluorides as partners in carbon-sulfur cross-coupling reactions is
interesting and expands the utility of this type of coupling.
A further use of a rhodium catalyst in carbon-sulfur bond-forming
reactions was reported by Lee and co-workers (Scheme 6.26).
86
Reaction
of rhodium cyclooctadiene chloride dimer, [RhCl(COD)]
2
, and PPh
3
in
thepresenceofsodiumtert-butoxide at 100 1C formed an active catalyst
to allow aryl iodides to couple with alkyl and aryl thiols. Whereas aryl
thiols are generally good coupling partners, only a few examples of the use
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