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Br
PdCl 2 (dppf)
Na 2 CO 3
n -Bu 4 NBr
Toluene/H 2 O
Reflux
MOMO
OMOM
MOMO
MOMO
74
OMOM
72%
Br
Br
MOMO
Br
+
56
Bpin
Bpin
+
Bpin
pinB
MOMO
OMOM
MOMO
OMOM
58a
Pd 2 (dba) 3
X-Phos
K 3 PO 4
1,4-dioxane/H 2 O
80˚C
35%
NaHSO 4
(20 eq.)
m -xylene
DMSO
reflux in air
OMOM
MOMO
OMOM
MOMO
25%
MOMO
OMOM
MOMO
OMOM
75
[13]CPPN
Fig. 38 Itami's synthesis of [13]CPPN [ 40 ]
Another path in which the science of cycloparaphenylenes is expanding is via
the inclusion of heteroatoms into the CPP backbone. Itami reported the synthesis of
[18]CPP with two 2,2 0 -bipyridyl units replacing four of the phenyl rings in the CPP
structure (Fig. 42 )[ 46 ]. This [14,4]CPPy was synthesized using established meth-
odology developed by the Itami group and shows a pH dependent fluorescence that
can be reversibly red shifted by addition of acid. These preliminary results may
open a door towards the controllable fluorescence of nitrogen-doped CPPs.
With their fluorescent properties, high conjugation, and host capability, these
nitrogen substituted CPPs are attractive materials for use as ligands and in metal-
organic structures. Indeed cycloparaphenylene synthesis in general is a new and
wildly exciting frontier in hydrocarbon synthesis. Material science applications of
carbon nanohoops are limited, at the moment, only by the availability of large
quantities of these unique molecules.
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