Chemistry Reference
In-Depth Information
Br
Bpin
Pd
2
(dba)
3
, X-Phos
B
2
pin
2
, KOAc
1,4-dioxane/H
2
O, 80˚C
Br
Bpin
95%
MOMO
MOMO
OMOM
72
OMOM
56
excess
55
Pd(PPh
3
)
4
Ag
2
CO
3
THF, reflux
65%
OMOM
Br
RO
OR
OMOM
Ni(cod)
2
, bpy
THF, reflux
Br
46%
RO
OR
MOMO
OMOM
RO
OR
60
MOMO
OMOM
73
NaHSO
4
·H
2
O
m
-xylene/DMSO
reflux under air
24%
[9]CPP
Fig. 36 Representative intramolecular macrocyclization route to [9]CPP [
45
]
4.6 Functionalized Cycloparaphenylenes
In 2011, Itami et al. expanded the field of cycloparaphenylene synthesis to include a
new class of macrocycle [
40
]. Representing the smallest unit cycle of a [
14
,
15
]
chiral carbon nanotube, naphthalene-included [13]CPPN, was synthesized by
modifying the selective synthesis of [12]CPP as developed by the Itami laboratory
(Fig.
38
). It was rationalized that this new molecule racemized between the M and P
isomers at room temperature via rotation of the 2,6-naphthyl moiety through the
center of the CPP cavity. It is, however, possible that a smaller CPPN may have
restricted isomerization. In principle, the extension of these and other arene-included
CPPs could lead to a host of CNT chiralities.
Amuch more complete model of ultrashort chiral CNTs was synthesized later that
year by Isobe et al. [
39
]. While not, strictly speaking, a cycloparaphenylene, these
cyclocrysenylenes (CC) exhibit atropisomerism, with rotation of each chrysenylene
unit through the [4]CC cavity geometrically disfavored. These macrocycles were
synthesized with an organometallic approach, similar to that used by Yamago
(Fig.
39
).
