Synthesis and Inclusion Properties of Carbonyl-Bridged Analogs of Acyclic p-t-Butylphenol–Formaldehyde Oligomers

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Abstract
A series of compounds in which a part or all of the methylene bridges of acyclic p-t-butylphenol–formaldehyde oligomers are replaced by C=O bridge(s) has been synthesized. The carbonyl-bridged tetramers, except for that with no methylene bridge, formed crystalline host–guest complexes with various organic compounds; those with two C=O bridges were superior regarding complexation, regardless of the position of the bridges. Exclusive guest selectivity of the tetramer with one terminal C=O bridge was observed for benzene and its methyl derivatives in a two-component system. The fully carbonyl-bridged dimer, trimer, tetramer, and pentamer had no complexing-capability. The thermal stability of benzene complexes (host : guest = 2 : 1) of the tetramers with one C=O bridge, as estimated from their thermal dissociation rates, are remarkably lower than that of the parent tetramer. Oximes derived from the tetramers with one C=O bridge were much more effective than the corresponding carbonyl-bridged ones regarding their complex-forming capability.