The preparation of inherently chiral rigidified calix[4]arenes with an intact cavity is a synthetic challenge due to the complicated synthesis of the starting compounds. Here, we report on a novel strategy for bridging the upper rim of calix[4]arenes consisting in carbonyl group formation and subsequent "extension" into a two-atom bridge using corresponding rearrangement reactions (Baeyer-Villiger, Beckmann). The resulting inherently chiral compounds are potentially applicable in the design of novel receptors. The complexation properties towards selected quaternary ammonium salts were studied by 1H NMR titration. Unusual complexation stoichiometries can be observed depending on the enantiomeric purity (racemic mixture versus pure enantiomers) of an amidic receptor 7 used.

Department of Analytical Chemistry UCTP 166 28 Prague 6 Czech Republic

Department of Organic Chemistry University of Chemistry and Technology Prague Technická 5 166 28 Prague 6 Czech Republic

Department of Solid State Chemistry UCTP 166 28 Prague 6 Czech Republic

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Upper rim-bridged calixarenes

Upper Rim-Bridged Calix[4]arenes via Cyclization of meta Alkynyl Intermediates with Diphenyl Diselenide