Regio-/stereoselective formation of monosulfoxides from thiacalix[4]arenes in all possible conformations

The Unexpected Chemistry of Thiacalix[4]arene Monosulfoxide

Thiacalix[4]arene monosulfoxide 4 possesses a very unusual chemistry, as demonstrated by several unprecedented derivatives in calixarene chemistry. Interestingly, compound 4 cannot be prepared by the dealkylation of its corresponding tetramethoxy derivative using BBr₃. Instead, the borate complex is formed with a boron bound by the two neighboring phenolic oxygens and a sulfoxide group. A similar type of borate complex with a spirodienone fragment was then isolated as a by-product. The oxidation of monosulfoxide with Chloramine-T did not provide the expected spirodienone moiety, but rather a complex oxathiane-based spiroheterocyclic part containing a chlorine atom. X-ray analyses confirmed the structures of the unusual products and feasible formation mechanisms were proposed. These results provide further evidence of the distinction between thiacalixarene chemistry and the chemistry of classical CH₂ analogues.

Inherent chirality through a simple dialkylation of 2,14-dithiacalix[4]arene

Dialkylation of 2,14-dithiacalix[4]arene offers the most straightforward way to inherently chiral calixarene-based macrocycles.

Chemoselective oxidation of phenoxathiin-based thiacalix[4]arene and the stereoselective alkylation of products

Phenoxathiin-based thiacalix[4]arene was subjected to exhaustive oxidation. Depending on the reaction conditions, the macrocyclic systems bearing four sulfonyl groups or three sulfonyl and one sulfoxide group are available in high yields.

Unexpected cleavage of thiacalix[4]arene sulfoxides

Thiacalix[4]arene monosulfoxides possess an unprecedented reactivity towards n-BuLi to form unusual linear structures.