Thiacyclophane cages and related bi- and tripodal molecules via transient polysulfenic acids

A series of bis- and tris-bridged thiacyclophane S-oxides, as racemates or meso products, have been synthesized with a new procedure. Starting from the corresponding thiols, in three steps, transient polyarene- and polyarylmethane-sulfenic acids were generated in the presence of di- and triethynylbenzenes. The thermal syn-addition of these sulfenic acids onto the triple bonds of the unsaturated acceptors was conducted in CH2Cl2 at 40 degrees C. The concentration of sulfoxide precursors of sulfenic acid and the sulfoxide/acceptor molar ratio addressed the syn-addition toward open-chain benzene sulfoxides or thiacyclophane S-oxides. Complete stereochemical control was observed in some reactions between polysulfenic acids and ethynylbenzenes, where the meso dithiacyclophane S,S'-dioxides were obtained exclusively, whereas 1:1 mixtures of meso/rac dithiacyclophanes S,S'-dioxides were isolated as products of other reactions. In almost all the cases, the obtained compounds were separated by column chromatography. The structure assignment of the new heterophanes was done on the basis of their diagnostic NMR spectra and X-ray crystallographic analysis of some of them. Open-chain polysulfinyl and polysulfinylmethyl benzenes, obtained as meso/rac mixtures, were separated and the products were fully characterized. Both synthesized cages, including trithia[3(3)](1,3,5)cyclophane S,S',S ''-trioxides, and bi- and tripodal benzene sulfoxides, appear promising in the field of coordination and material chemistry.