Homothiacalixarenes are similar to the calix[n]arene macrocycles commonly used in host–guest chemistry. They differ in that the calixarene’s methylene bridges are partly or completely replaced by CH₂SCH₂ bridges. Homothiacalixarenes have received little attention to date, despite the fact that their structural features are particularly attractive for supramolecular host–guest chemistry.

Wim Dehaen and co-workers, Katholieke Universiteit Leuven, Belgium, optimized the synthetic macrocyclization protocols to obtain homothiacalix[4]arene by a straightforward one-pot macrocyclization approach that involves substitution reactions of 1,3-bis(mercaptomethyl)benzene nucleophiles on 1,3-bis(bromomethyl)benzene derivatives under basic conditions. Homothiacalix[4]arenes were obtained with improved yields of up to 62 % compared with previous syntheses. This allowed their structures to be characterized by solution-phase NMR spectroscopy and solid-state X-ray spectroscopy.

This new protocol will hopefully lead to the increased use of homothiacalixarenes in host–guest chemistry such as in chemical sensors.

• Homothiacalix[4]arenes: Synthetic Exploration and Solid-State Structures
  J. Thomas, K. Van Hecke, K. Robeyns, W. Van Rossom, M. P. Sonawane, L. Van Meevelt, M. Smet, W. Maes, W. Dehaen,
  Chem. Eur. J. 2011.
  DOI: 10.1002/chem.201101690