Chemistry Reference
In-Depth Information
) of indenocorannulene family
a
Table 6 POAV pyramidalization angles (deg) and bowl depths (
Å
G
{
inv
(kcal/mol) References
98 8.9, 9.8, 11.2 1.07 29.8 (calcd.) [
27
,
128
]
100 8.8, 9.8, 10.8 1.04
>
24 [
27
]
101a 10.4, 10.9, 11.2 1.21 - [
128
]
101b 8.9, 9.8, 11.8 1.16 - [
128
]
103a 11.1, 11.5, 12.0 1.30 - [
128
]
103b 10.3, 11.8, 12.4 1.27 - [
128
]
102 11.4, 12.1, 12.5 1.38 - [
89
,
128
]
104 12.7 1.43 - [
89
,
128
]
a
POAV pyramidalization angles at the interior five-membered ring carbon atoms of the indenocor-
annulenes, and the values obtained by averaging the POAV angles of symmetry-related carbon
atoms
POAV
a
Compound
Bowl depth
ʔ
'benzo' ring in 100 is formed by a formal [(2+2)+2] cycloaddition of the diynyl
moiety in 99 with an external alkyne (Vollhardt and coworkers used the strategy
of alkyne cyclotrimerization to make polycyclic aromatic compounds; for details,
see [
127
]). This synthetic approach allows a variety of functional groups to be
regioselectively introduced.
Scott and coworkers improved the synthesis of indenocorannulene 98 by
conducting Pd-catalyzed intramolecular arylation reaction of (2-chlorophenyl)-
corannulene 29 under microwave-assisted conditions (Scheme
30
)[
128
]. The effi-
cient condition allows a simple formation of multi-indenocorannulenes. Tetrakis-
(2-chlorophenyl)corannulene 42 and pentakis(2-chlorophenyl)corannulene 50 were
prepared by the Suzuki couplings of the corresponding halocorannulenes with
2-chlorophenyl boronic acid [
89
], as shown in Schemes
10
and
13
. Subsequently,
Pd-catalyzed cyclization of 42 and 50 gave tertaindenocorannulene 102 and penta-
indenocorannulene 104, respectively. Diindenocorannulenes 101 and triindeno-
corannulenes 103 were generated from regioisomeric mixtures of
dibromocorannulenes and tribromocorannulenes, but the pure form of these products
can be obtained. It should be noted that pentaindenocorannulene 104 is a possible
precursor to the
C
5
v
end-cap of single-walled, “armchair” [5,5]nanotube.
2.5.2 Structures and Properties
The solid-state structures of the indenocorannulenes have been systematically stud-
ied. In contrast to the parent compound 98 [
128
], the substituted indenocorannulene
100 (R
1
R
2
R
4
R
5
CO
2
Me, R
3
Ph) [
27
] is slightly flattened, revealed by com-
paring their bowl depths and the POAV pyramidalization angles (Table
6
).
Each additional indenoannulation increases the bowl depth and the curvature.
Pentaindenocorannulene (104) is determined to have deepest bowl depth (1.43
¼
¼
¼
¼
¼
)
and the highest POAV pyramidalization angle (12.7
)[
89
,
128
]. This curvature is
significantly more pyramidalized than C
60
.
Å
