Monosulfinyl Thiacalix[4]biscrown-5 and Its Crystal Structure

Abstract

Calixarenes have been used as suitably preorganized building blocks for the construction of more elaborate structures, receptors and molecular assemblies.1 As one of calixarene family, thiacalixarenes having four sulfur atoms instead of methylene bridges have attracted considerable interest as a ligating agent bearing additional coordination sites, modifying the dimensions of the cavity.2 Unlike calix-[4]arenes, thiacalix [4]arenes showed affinity for transition metal ions because the sulfur atoms in the calixarene framework take part in the metal ion complexation. 4 It was also reported that 1,3-thiacalix[4]mono(crown-5 and crown-6) ethers in the 1,3-alternate conformation could be prepared by condensation of 1,3-dialkoxythiacalix[4]arenes with polyethylene glycol ditosylates or diiodides. 5 We recently reported that thiacalix[4]bis(crown-5 and crown-6) compounds behave as K + and Cs + ion receptors, respectively, but showed a low binding ability, which was proven by Xray crystallography and NMR chemical shift change. 6Oxidation of the sulfur atoms of the thiacalix[4]arene into sulfinyl and sulfonyl groups, giving novel building blocks that could find many possible applications in supramolecular chemistry, has previously been described. 5,7 This led us to investigate the oxidation of thiacalix[4]biscrown-5. We report herein the synthetic method and the physical properties and crystal structure of the resulting molecules.In a first step, para-tert-butylphenol was cyclized with sulfur to give para-tert-butylthiacalix [4]