Synthesis and conformational study of the first triply bridged calix[6]azatubes.
[reaction: see text] The first C(3)(v)- and D(3)(h)-symmetrical triply bridged calix[6]azatubes were prepared in good yields from the known 1,3,5-tris-methylated calix[6]arene through an efficient [1 + 1] macrocyclization reaction. A remarkably regioselective hexa ipso-nitration reaction led to a calix[6]azatube substituted at the wide rim in alternate position by tBu and nitro groups. A (1)H NMR study showed that, whereas the parent bis-calix[6]arenes self-include their methoxy groups, thereby closing their inner tube, the nitro-substituted calix[6]azatube undergoes a conformational change with the expulsion of the methoxy groups, hence presenting a three-dimensional structure open for host-guest applications.
Le Gac
Stéphane
S
Faculté des Sciences et Techniques, URCOM, Université du Havre, 25 rue Philippe Lebon, BP 540, 76058 Le Havre Cedex, France.
Zeng
Xianshun
X
Reinaud
Olivia
O
Jabin
Ivan
I