Chemistry Reference
In-Depth Information
R
Si(
i
Pr)
3
X
X
Pd(0), CuI, R
3
N
X
X
33
X = H
(93%)
34
X = Cl
(65%)
+ 2
I
I
X
X
X
X
32
R
X
X
X
X
hv,
furan
1. Bu
4
NF, AcOH
THF, rt
2.Cu(OAc)
2
pyridine, rt
18%
X
X
X
X
37
X
X
X
X
X
X
X
X
X
X
X
X
hv
observed
X
X
35
X = H
(79%)
36
X = Cl
(75%)
X
X
Fig. 17 Tobe's synthesis of [2
6
]CPPA [
34
]
4.1 Early Attempts Towards Cycloparaphenylenes
The first published attempt at the synthesis of any CPP was reported in 1934 by
Parekh et al. [
3
]. Having synthesized the parent macrocycle,
p
,
p
-diphenylenete-
trasulfide, 38, the thermal liberation of 4 equiv. of sulfur (as copper sulfides and
sulfur oxides) upon heating with copper in air was attempted (Fig.
19
). Only partial
desulfination was observed, however, probably owing to the extreme strain
associated with the resulting [2]cycloparaphenylene.
Almost 60 years later, V¨gtle and coworkers published three inspiring, synthetic
routes towards CPP [
59
]. First, in a similar fashion to the attempts towards [2]CPP
