Efficient synthesis and host-guest properties of a new class of calix[6]azacryptands.
Two members of a new class of calix[6]azacryptands, namely, calix[6]tampo and calix[6]tamb, have been synthesized through an efficient [1 + 1] macrocyclization reaction--reduction sequence. One of them has been obtained in a remarkably high overall yield from the known X(6)H(3)Me(3). In comparison to all the other calix[6]azacryptands, they possess unique conformational properties since they present a rigidified cone conformation with a partial filling of the cavity by the methoxy groups. In contrast to calix[6]tampo, the fully protonated derivative of calix[6]tamb behaves as a remarkable molecular receptor toward polar neutral guests. NMR studies have shown that the intracavity binding process is governed by a conformational flip of the aromatic walls of the calixarene core.
Gac
Stéphane Le
SL
Université Libre de Bruxelles, Service de Chimie Organique, Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium.
Zeng
Xianshun
X
Girardot
Camille
C
Jabin
Ivan
I