Synthesis and conformational studies on hexa-O-alkyl p-unsubstituted calix[6]arenes.
[structure: see text] In this article we describe the selective O-benzylation of para-unsubstituted calix[6]arene 1 in rings 1 and 4 (2a-c) and the subsequent alkylation of phenol groups with alpha-haloesters (methyl esters 3a, 3c, and 3e; tert-butyl esters 3b, 3d, and 3f) to determine the effect of these groups on their conformational behavior. 2D NMR studies at 188 K reveal that compounds 2a-c, 3b, 3d, and 3f are less flexible, showing a 1,2,3-alternate conformation. The same conformation has been observed in the solid state.
Iglesias-Sánchez
José C
JC
Departamento de Química Orgánica and Servicio Interdepartamental de Investigación, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain.
Souto
Beatriz
B
Pastor
César J
CJ
de Mendoza
Javier
J
Prados
Pilar
P