CALIXARENES .25. CONFORMATIONS AND STRUCTURES OF THE PRODUCTS OF ARYLMETHYLATION OF CALIX[4]ARENES

The arylmethylations of calix[4]arenes reported in this paper serve as companion pieces to an earlier study of the effects of reaction conditions and the structure of the derivatizing agent on the conformational outcome of the aroylation of calix[4]arenes. In contrast to the aroylation reaction, where a significant and predictable relation is observed between the para substituent of the aroyl chloride and the ratio of conformers formed, the arylmethylation reaction shows only a small and much less easily predictable dependence of the conformer ratio on the para substituent of the arylmethyl halide. Also, whereas the products of aroylation are the cone and/or 1,3-alternate conformers, those of arylmethylation are the cone and/or partial cone conformers. While no rationale has yet emerged to explain this difference, a study of the benzylation of dibenzyl and tribenzyl ethers of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]arene has established that the conformations of the tetraethers are not completely established until the third step in some cases and the fourth step in others.