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Conformational Restriction of the Calix[6]arene Macrocycle by the Ritter Reaction
Author(s) -
Vatsouro Ivan M.,
Shokova Elvira A.,
Shestakova Alla K.,
Chertkov Vyacheslav A.,
Kovalev Vladimir V.
Publication year - 2006
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200500604
Subject(s) - chemistry , ritter reaction , trifluoroacetic acid , alkylation , regioselectivity , stereochemistry , calixarene , conformational isomerism , alcohol , medicinal chemistry , organic chemistry , molecule , catalysis
Herein we report on the development of a novel and efficient approach to the restriction of the conformational mobility of calix[6]arenes. The method involves the addition of tertiary alcohols to calix[6]arenes with one, three and six cyanomethoxy groups attached to the lower rim under modified Ritter reaction conditions. Alkylation of monocyanomethoxy‐ p‐tert ‐butylcalix[6]arene ( 1 ) and 37,39,41‐trimethoxy‐38,40,42‐tricyanomethoxy‐ p‐tert ‐butylcalix[6]arene ( 2 ) with 3‐R‐1‐adamantanols (R = H, CH 2 COOH) in trifluoroacetic acid afforded the corresponding mono‐ and triamides with cone‐like conformations. The partial alkylation of hexanitrile derivatives showed unexpected regioselectivity. Addition of 1‐adamantanol or tert ‐butyl alcohol to hexacyanomethoxy‐ p ‐X‐calix[6]arenes 3a – c (X = tert ‐butyl, 1‐adamantyl, 3‐methoxycarbonylmethyl‐1‐adamantyl) gave 37,40‐dinitrile‐38,39,41,42‐tetraamides as the major products. These tetraamides are conformationally restricted in solution over a wide range of temperatures and adopt a flattened 1,2,3‐alternate conformation, as shown by 2D and variable‐temperature NMR experiments. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)