Table 34 N-Arylation of imidazole with various arylboronic acids using CELL-Cu(0) catalyst
a
N
N
N
N
N
N
N
N
N
N
N
N
Cl
F
F 3 C
H 3 C
H 3 COC
H 3 COC
B(OH) 2
H 3 C
B(OH) 2
F 3 C
B(OH) 2
F
B(OH) 2
Cl
B(OH) 2
B(OH) 2
Substrate
Product
Time (h)
Yield (%)
b
2.5
2.5
2.5
2.5
4.0
5.0
5.0
B(OH) 2
OCH 3
OCH 3
N
N
98
82
87
83
c
93
95
80
77
c
83
Entry
1
2
3
4
5
6
7
8
H 3 CO
B(OH) 2
N
N
H 3 CO
5.0
86
87
c
80
d
a Reaction conditions: imidazole (1 mmol), triethylamine (2 mmol), CELL-Cu(0) catalyst
(0.025 g), phenylboronic acid (1 mmol), methanol (5 ml), reflux
b
Isolated yields
c
Yield after fourth cycle
d
Reaction performed at room temperature for 18 h
N
N
+
( )
3
Br
-
N
N
+
( )
3
PF 6
-
N
N
+
( )
3
BF 4
-
No reaction
80%
95%
n-Bu 4 Br
No reaction
Fig. 4 Screening of ILs for the N-arylation of imidazole (1 mmol) with phenylboronic acid
(1 mmol) using 10 mol% Cu(OAc) 2 ÁH 2 O at 70
C in 3.0 h
Recent Developments in Recyclable Copper Catalyst Systems for C–N Bond. . .
161