Chemistry Reference
In-Depth Information
Table 5 The inversion barrier (kcal/mol) and the bowl depth (
)of
peri
-annelated corannulenes
Å
Exptl.
RHF/cc-pVDZ
B3LYP/cc-pVDZ
ʔG
{
inv
ʔG
{
inv
ʔG
{
inv
Compound
Bowl depth
Bowl depth
References
67
-
29.2
1.05
27.7
1.08
[
57
]
27.6
a
69
26.6
1.04
25.6
1.07
[
57
,
61
]
70
17.3
14.8
0.91
14.7
0.95
[
57
]
71
13.9
12.1
0.86
11.8
0.90
[
57
]
72
15.5
-
-
-
[
57
]
73
16.1
14.3
0.90
13.9
0.94
[
57
]
74
13.0
-
-
-
[
57
]
a
Determination from [D
2
]-69
1) CH
3
OCHCl
2
TiCl
4
, CH
2
Cl
2
LiAlH
4
, AlCl
3
2) NaOEt
EtOH, THF
34%
Et
2
O
18%
t-Bu
O
O
76
t-Bu
27
t-Bu
75
Scheme 21 Synthesis of phenalene 76 [
47
]
corannulene (34) (Scheme
20
)[
57
]. These compounds provide suitable models for
systematically studying the influences of substituents and ring size on the inversion
dynamics (Table
5
).
Phenalene derivative 76 was synthesized from 1 in four steps (Scheme
21
)
[
47
]. Ketone 27, which was generated in 99% yield by Friedel-Crafts acylation
of 1 as shown in Scheme
7
, underwent the
peri
-formylation and the subsequent
intramolecular aldol condensation to give phenalenone derivative 75. The treatment
of 75 with a mixture of LiAlH
4
and AlCl
3
afforded 76. It was observed that
compound 76 is not stable in air because it generates 75 under aerobic conditions.
In contrast, the anion Li
+
·76
, which was prepared by the treatment of 76 with an
equimolar amount of
n
-BuLi, is highly stable in a degassed solution. The inversion
barriers of 76 and its derivatives were systematically investigated based on com-
putational analysis. The distribution of the negative charge on anionic 76 causes it
to be flatter and easier to invert than the neutral. For example, the neutral radical
species has a higher inversion barrier (12.6 kcal/mol) than that of the monoanion
(11.3 kcal/mol).
Furan-fused corannulene 77 was efficiently prepared by a brief heating of 31 with
3,6-di(2-pyridyl)-1,2,4,5-tetrazine in chloroform (Scheme
22
)[
107
]. Isocorannu-
lenofuran 77 is a reactive diene for the Diels-Alder reaction (see Scheme
34
)
[
108
]. Difuran-fused corannulene 79 can be generated from
syn
/
anti
-78, which is
prepared by treatment of a solution tetrabromocorannulene 18 in THF with
tert
-butyl
