New chiral upper and lower rim (R)-binaphthyl-bridged
calix[4]arenes in the cone conformation
(5, 10, 11, 15,
17, 18) have been synthesized by exploiting the
selective functionalization of the
calix[4]arene skeleton. The conformational properties
of the new hosts in CDCl3 and
DMSO-d
6
have been clarified by dynamic NMR measurements, and their complexation
properties toward
neutral molecules, alkali metal, and silver(I) cations have been
explored. The upper rim binaphthyl-bridged calix[4]arene 5 is able to form a 1:1
complex with Ag+ in
CDCl3:CD3OD 1:1 v/v solution,
where the silver cation is encapsulated into the apolar cavity.
The determined association constant
(log K = 3.51) is substantially higher than for unbridged
calix[4]arenes in the cone
conformation.
These new macrobicyclic compounds are potential hosts for chiral
recognition and catalysis.
A one-pot procedure, which combines the Ritter and Friedel-Crafts reactions, produced the first members of a new type of calix[4]arene-based receptors. The cavity in these receptors is formed by a calix[4]arene framework fixed in the cone conformation and bulky adamantyl or (and) phenylacetylene moieties. Amido and amino groups were used as potential hygrogen bond donors. Preliminary studies revealed interesting complexation properties, in particular, the tetrahedral recognition of water molecules performed by one of the receptors.
Calix[4]arene derivatives are used as a scaffold for the attachment of chiral substituents. Calix[4]arenes having either lower or upper rim capped with chiral binaphtholic species 5 and 6, as well as new biscalix[4]arenodiaza-18-crown-6 (8), have been synthesized.
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