Synthesis of upper rim-double-bridged calix[4]arenes bearing seven membered rings and related compounds.

Meta / meta - and meta / para -disubstituted organomercury calix[4]arenes in the cone conformation were transformed into corresponding amino derivatives. Acylation and subsequent intramolecular cyclization using the Bischler-Napieralski reaction provided, in the case of the meta / meta -series, double bridged calixarenes possessing seven membered rings on the upper rim. A similar synthetic strategy applied to meta / para -isomers allowed for the isolation of monobridged compounds bearing an additional trifluoroacetamido group located distally to seven-membered rings. Both series represent inherently chiral systems, which were successfully resolved using preparative chiral HPLC. The pure enantiomers exhibited a recognition ability towards selected chiral guest molecules as documented by the 1 H NMR titration experiments. The absolute configuration of the phenyl-substituted enantiomer ( meta / meta -) was confirmed by single crystal structure determination (X-ray).