フェノール類のラジカル制御酸化重合

概要

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A new methodology of polymer synthesis, radical-controlled oxidative polymerization of phenols unsubstituted at ortho position (s) with high regioselectivity catalyzed by a tyrosinase model complex, is described. This catalyst forms only basic μ-η<SUP>2</SUP>:η<SUP>2</SUP>-peroxo dicopper (II) complex 1 as the active oxygen complex, and 1 reacts with phenols to give phenoxo-copper (II) complexes 2, equivalent to phenoxy radical-copper (I) complexes 3. These species 2 and/or 3 are not free radicals but controlled radicals, and hence all the couplings of the controlled radicals are regulated by the present catalyst. On the other hand, the oxidative polymerization by conventional catalysts includes free radical formation process, in which the coupling selectivity cannot be controlled by the catalysts. By the radical-controlled method, oxidative polymerization of 4-phenoxyphenol produces crystalline poly (1, 4-phenylene oxide) for the first time. From 2, 5-dimethylphenol, novel crystalline poly (2, 5-dimethyl-1, 4-phenylene oxide) with a melting point above 300°C has been developed. It is also discussed how C-O/C-C coupling selectivity for 2, 6-dimethylphenol is controlled by use of conventional catalyst, which must generate its free radical.
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