Chemistry Reference
In-Depth Information
Ph
[Cp*RhCl
2
]
2
(1 mol %)
Cu(OAc)
2
H
2
O (5 mol %)
DMF, air, 100 ºC, 2h
67%
H
Ph
Ph
B(OH)
2
Ph
157
158
Scheme 41 Rh-catalyzed annulation of aryl boronic acids [
98
]
Mo-Cat
CS
2
, 25 ºC, 1h
160
i
-Pr
i
-Pr
159
68%
N
Mo
(CF
3
)
2
MeCO
Ph
(CF
3
)
2
MeCO
Mo-Cat
CS
2
, 25 ºC, 1h
Mo-Cat
161
162
79%
Scheme 42 Metathesis as a means to build up graphene-type structures [
102
]
2.6 Ring Closing Metathesis
Beside the coupling of two aromatic fragments or the cyclization of alkynes to form
graphene-type structures, ring closing metathesis of olefins has been applied to the
preparation of aromatic compounds [
99
,
100
]. Not only simple monocyclic benzene
derivatives can be synthesized [
101
] but also larger graphene-type structures have
been realized using olefin metathesis. An impressive example by King and
coworkers nicely demonstrates the utility of the metathesis reaction (Scheme
42
)
[
102
], once more justifying the award of the Nobel Prize in 2005 for this
transformation.
3 Synthetic Methods for the Extension of Graphene-Type
Structures
The perfect graphene sheet extends indefinitely, representing an ideal 2D polymer
[
103
-
105
]. Most examples shown so far described the synthesis of distinct molec-
ular PAHs. In order to harvest the unique properties of graphene, the small PAH
fragments have to be further extended [
106
]. In principle most strategies explained
above have the potential to achieve this goal. A small number of selected examples
are illustrated below, demonstrating the basic concepts.
