Synthesis of poly (vinylcatechols)†

Abstract

Five vinylcatechol precursors have been synthesized by either alcohol dehydration or Wittig coupling techniques. Dehydration of the appropriate sec-phenethyl alcohol is the most efficient synthetic approach: the following monomers (yields) are reported: 5-vinyl-1,3-benzodioxole, I (63%); 3,4-dimethoxystyrene, II (45%); 2,3-dimethoxystyrene, III (85%);6-vinyl-1,4-benzodioxane.IV(65%); and4-vinyl-l,3-benzodioxole, V(50%). The monomers can be converted by free-radical techniques to polymers with molecular weights up to 95,000. Monomers I, II, IV, and V polymerized in the presence of stannic chloride; monomers I, III, and IV yielded polymers upon treatment with butyllithium. With the exception of poly IV, the blocking groups can be removed by treatment with boron trichloride followed by methanolysis to liberate poly(3-vinyl- or 4-vinylcatechol). Suprisingly, the stability of the catechol polymers depends upon the substituent distribution; poly(3-vinylcatechol) is more stable than any polycatechol previously reported. It is soluble in methanol, autooxidizes very slowly, but can be oxidized by ceric ammonium nitrate to poly(3-vinyl-1,2-benzoquinone).