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Research Article
ScienceAsia 26 (2000) : 163-170 |doi: 10.2306/scienceasia1513-1874.2000.26.163
Synthesis of Tetraalkylated Calix[4]arenes
and Studies of Their Conformational Behaviors
Sudarath Veravong, Vithaya Ruangpornvisuti, Bongkot Pipoosananakaton,
Mongkol Sukwattanasinitt and Thawatchai Tuntulani*
ABSTRACT: Three new tetraalkylated calix[4]arenes, 25,27-[N,N'-di-((2-ethoxy)benzyl)propylene diamine]-26,28-dimethoxy-p-tert-butylcalix[4]arene dihydrochloride, 7, 25,27-[di(2-ethoxy)
nitrobenzene]-26,28-dimethoxy-p-tert-butylcalix[4]arene, 10, and 25,27-[di(2-ethoxy)azobenzene]-26,28-dimethoxy-p-tert-butylcalix[4]arene, 11, have been synthesized. These compounds underwent
the conformational interconversion of the calix[4]arene unit which could be studied by variable
temperature 1H NMR experiments. Rates of conformational interconversion of 7 were determined to be
111.0 s-1 and 94.6 s-1 in DMSO-d6 at 50oC and CD3OD at 27oC, respectively. In CDCl3 at –30oC, compound
10 was found to exist in both cone and partial cone conformations with the ratio of 43:57. Cyclization
of 10 by reductive coupling to 11 confined the calix[4]arene unit in cone conformation. The compound
11 in CDCl3 then underwent conformational interconversion upon isomerization of the azobenzene
unit leading to mixed conformations of calix[4]arene.
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Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
* Corresponding author.
Received 22 Feb 2000, Accepted 9 May 2000
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