Ordered polyesters and polyester-sulfones: aromatic nucleophilic substitution reactions involving diaryl ethers

Synthesis of methyl substituted phenols (via various diazonium salts), to be used as a monomer in the synthesis of ordered polyesters and to study the liquid crystal continuum from monomer-to-oligomer-to-polymer, was attempted. Deblocking of di(methoxyphenyl) terephthalates with sodium ethanethiolate in dimethylformamide resulted in the preferential cleavage of the ester linkage over the alkyl -aromatic ether linkage. A number of cleavage products resulted, depending upon the reaction conditions. 4,4\u27[sulfonyl bis(ρ-phenylene ether)] dianisole was prepared as a model compound to be used in the ordered poly(ester-sulfone) study. Deblocking with hydrobromic and hydrobromic acid-acetic acid cosolvents was successful. However, deblocking wtih sodium ethanethiolate in dimethylformamide resulted in preferential cleavage of the aryl-aryl ether linkage over the alkyl-aromatic ether linkage. Attempts to synthesize 4,4\u27-[sulfonyl bis(p-phenylene ether)] dianisole by the Ullmann sythesis of diaryl ethers was unsuccessful. The effect of para-substituents on aromatic-nucleophic substitution reactions, in cleavage reactions of diaryl ethers by sodium ethanethiolate in diamethylformamide, was studied. Electron-withdrawing groups were found to facilitate the cleavage reaction