Unexpected cleavage of thiacalix[4]arene sulfoxides

Abstract

Thiacalix[4]arenes having one bridge oxidized to a sulfoxide moiety can react with organolithium reagents to form cleaved structures which are otherwise difficult to access. Cleavage of the macrocyclic skeleton is independent of the starting conformation as proven by the same product obtained from the corresponding cone, partial cone or 1,3-alternate derivatives. Quenching of the crude reaction mixture with D₂O allowed elucidation of the mechanism which is based on the ligand exchange of the sulfoxide functionality. The general applicability of this reaction was demonstrated using the corresponding distal or proximal disulfoxide derivatives, while the quenching of the reaction mixture using various electrophiles allowed the isolation of the corresponding mono- and di-substituted oligomers. The structure of the unexpected product (a tetrameric derivative) was assigned by single crystal X-ray crystallography.