Chemistry Reference
In-Depth Information
t
Bu
t
Bu
Pd(OAc)
2
(5 mol %)
Choranil (2 equiv)
B
O
DCE, 80 ºC
3
t
Bu
t
Bu
115
114
116
FeCl
3
t
Bu
t
Bu
60% (over 2 steps)
117
Scheme 28 C-H functionalization of pyrene using Pd-catalysis [
73
]
7 eq Cu(0)
DMF
140-150°C
O
O
R
1
O
O
R
1
I
I
+
90-98%
R
1
,R
2
, R
3
= H, NO
2
R
3
R
2
R
2
R
3
119
118
120
Scheme 29 Example for an intermolecular Ullmann reaction [
76
]
3 eq. K
0
, THF
pressure vessel,
85 ºC, overnight
122
121
>95%
Scheme 30 Reductive coupling of C-H bonds [
77
]
reducing agent [
75
]. In the example shown in Scheme
29
, two different building
blocks have been connected utilizing the different electronic properties of each of
the coupling partners [
76
].
C-C bonds can also be built under reductive conditions. In this case elemental
potassium, which is usually employed as a reducing agent, is able to connect two
carbon atoms accompanied by the evolution of H
2
(Scheme
30
). The exact mecha-
nism is still under debate, although a radical chain reaction involving free hydrogen
atoms (H
) in the two-step propagation cycle is proposed [
77
].
