Sulfone-Linked Paracyclophanes via Macrocyclic Aromatic Thioethers: Synthetic and Structural Investigations

Reaction of 4,4′-sulfonylbis(benzenethiol) with 4,4′-dichlorodiphenylsulfone under pseudo-high-dilution conditions leads to macrocyclic thioethersulfones [-S-Ar-SO2-Ar-]n (Ar=1,4-phenylene). These include a highly strained [1+1] cyclodimer (n=2), a cyclotrimer resulting from thioether-exchange reactions, and a [2+2] cyclotetramer which can adopt two entirely different conformations in the crystalline state, one having molecular D2d (“tennis-ball-seam”) symmetry. The same type of reaction is successful using 4,4′-thiobis(benzenethiol) instead of 4,4′-sulfonylbis(benzenethiol) and affords macrocycles with a higher ratio of thioether to sulfone linkages. Exhaustive oxidation of macrocyclic thioethersulfones with hydrogen peroxide affords a series of sulfone-linked paracyclophanes, [-Ar-SO2-]4, [-Ar-SO2-]6, [-Ar-SO2-]8 and [-Ar-SO2-]12. Single crystal X-ray analysis reveals [Ar-SO2-]4 to be a near-perfect square box, whilst the cyclic hexamer [-Ar-SO2-]6 adopts a much more irregular conformation, and [-Ar-SO2-]8 displays a “double-box” structure clearly related to that of [Ar-SO2-]4.