Synthesis and solid state structural analysis of conformers of tetrakis((ethoxycarbonyl)methoxy)tetrathiacalix[4]arene

The role of alkaline metal cations in the synthesis and in determining the conformer distribution of tetrakis((ethoxycarbonyl)methoxy)tetrathiacalix[4 ]arene obtained by treatment of tetrathiacalix[4]arene 1 in acetone by ethy l bromoacetate in the presence of M2CO3 was systematically investigated. Am ong the four possible conformers, the cone, partial cone and 1,3-alternate conformers were obtained, purified and structurally characterised by X-ray analysis in the solid state. Although for Li+ no tetra substituted derivati ve was observed, for Na+ the cone conformer was exclusively formed while fo r both K+ and Cs+ a mixture of partial cone and 1,3-alternate conformers wa s obtained. (C) 1999 Elsevier Science Ltd. All rights reserved.