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Synthesis and Conformational Studies on Hexa-O-alkyl p-Unsubstituted Calix[6]arenes

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journal contribution
posted on 09.12.2005, 00:00 by José C. Iglesias-Sánchez, Beatriz Souto, César J. Pastor, Javier de Mendoza, Pilar Prados
In this article we describe the selective O-benzylation of para-unsubstituted calix[6]arene 1 in rings 1 and 4 (2ac) and the subsequent alkylation of phenol groups with α-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 2ac, 3b, 3d, and 3f are less flexible, showing a 1,2,3-alternate conformation. The same conformation has been observed in the solid state.