Chemistry Reference
In-Depth Information
Li
O
O
HO
OH
Cu, 400°C
33%
23%
HO
OH
O
O
7
8
9
Scheme 3 Synthesis of HBC by Clar et al.
R
R
R
1) AlCl
3
, 120°C
2)Cu, 400°C
O
OH
Li
0.4%
15-50%
OH
O
R=H, Me
10
R
R
11
12
Scheme 4 Synthesis of HBC by Schmidt et al. [
23
]
O
O
O
Soda-lime
400°C vaccum
O
O
O
14
13
15
16
overall yield: 25%
Scheme 5 Synthesis of coronene 16 [
22
,
24
]
The same approach was followed by Schmidt et al. to access substituted HBCs
12, using a substituted phenyl-lithium reagent [
23
] (Scheme
4
). For the first time,
structure-property relationships could be systematically addressed with this reliable
route to differently substituted HBCs. In this case the UV and IR spectroscopic
properties were investigated. Indeed, a methyl substituent intensifies the 0-0
transition of the
band due to the different symmetry compared to the unsubstituted
HBC (Symmetry D
6h
). Additionally, the substitution increased its solubility.
The extension of PAHs using maleic anhydride in the presence of an oxidizing
agent was also explored by Clar and Zander. The decarbonylation took place with
soda-lime under vacuum sublimation. Coronene 16 and ovalene were synthesized
by this method (Scheme
5
)[
22
,
24
].
α
