Synthesis and Inclusion Properties of Sulfur-Bridged Analogs of Acyclic Phenol-Formaldehyde Oligomers

A series of compounds in which a part or all of the methylene bridges of acyclic p-methyl- and p-t-butylphenol–formaldehyde tetramers were replaced by sulfur bridge(s) was synthesized. It was found that though the sulfur-bridged tetramers formed crystalline host-guest complexes with a variety of organic compounds, they were different from the parent tetramers regarding their inclusion behavior. The number and position of the sulfur bridge(s), as well as the p-substituent of phenol in the tetramers, had a great influence upon the inclusion property. The thermal stability of complexes of the sulfur-bridged tetramers (SSS-a,b) with benzene, as estimated from their thermal dissociation rates, are lower than those of the parent tetramers (CCC-a,b).