Chemistry Reference
In-Depth Information
O
O
O
O
H
H
91
H
H
O
O
O
17%
H
H
H
H
92
O
O
93
1. TiCl
4
, LiAlH
4
2. Ac
2
O, HCl
56%
94
Fig. 45 Stoddart's attempted synthesis of [6]
12
cyclacene [
71
]
R
R
reflux
dioxane
R
R
R
R
95
O
O
R
R
69%
O
O
O
O
97
R =
n
-hexyl
O
O
96
Fig. 46 Cory's attempted synthesis of [6]
8
cyclacene [
72
]
6.2 Towards the Synthesis of [6]
8
Cyclacene
In 1996, Cory reported attempts to access [6]
8
cyclacene from macrocycle 97
(Fig.
46
). Building upon the macrocyclization work of Schl
ยจ
ter, this molecule
was easily synthesized from the reaction of flexible bisdiene 95 with rigid and
planar anthrodiquinone 96 [
73
].
In this way Cory avoided issues of diastereoselectivity and was able to isolate 97
in 69% yield. Alkyl chains were used to avoid the problem of solubility encountered
by Stoddart [
72
]. Several attempts were made to convert unstrained 97 into
[6]
8
cyclacene including a host of oxidation and deoxygenation conditions, but
formation of the cyclacene was never observed [
72
]. Again, only pathways with
oxidative and acidic conditions in the final steps were explored. As previously
mentioned, the desired product is likely very unstable in such conditions.
