A NOVEL ROUTE TO CALIX[4]ARENES .2. SOLUTION-STATE AND SOLID-STATE STRUCTURAL-ANALYSES AND MOLECULAR MODELING STUDIES

A versatile route to a series of C-alkylcalix[4]resorcinarenes has bee n developed, using 2,4-dimethoxycinnamates as starting materials under carefully controlled reaction conditions employing BF3 as a Lewis aci d catalyst. Depending on the reaction conditions and the nature of the ester side chain in the cinnamates, the calixarenes can adopt 1,2-alt ernate, 1,3-alternate, or flattened-cone conformational states. An ext ensive study, relating to the influence of the Lewis acid, temperature , and reaction time, has provided information on the relative ratios o f the different conformations and their interconversion. Structural as signments are based on detailed spectroscopic analyses including X-ray analyses. The latter provide evidence of their molecular structure an d shape in the solid state. A detailed molecular modeling study has be en completed and is described. From the data obtained, good agreement with NMR data, X-ray analyses and experimental results is observed.