2- Bromo-4,5-dimethylphenol

Halogen Displacement. Poly(phenylene oxide)s can also be prepared from 4-halo-2,6-disubstituted phenols by displacement of the halogen to form the ether linkage (48). A trace of an oxidizing agent or free radical initiates the displacement reaction. With 4-bromo-2,6-dimethylphenol, the reaction can be represented as in equation 10 ... 

Asymmetric hydrogenation of itaconic acids.1 Japanese chemists have prepared a new bisphosphine ligand (2), which is more efficient than DIOP for asymmetric hydrogenation of itaconic acids when complexed with rhodium. It is available in four steps from 4-bromo-2,6-dimethylphenol. 

Copolymerization of 4-bromo-2,6-dimethylphenol with 2,4,6-trimethylphenol, 4-t-butyl-2,6-dimethylphenol, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 4-hydroxy-3,5-dimethylbenzyl alcohol and a 4-substituted-2,6-di-r-butylphenol are discussed269. 

The telechelica,(i -bis(2,6-dimethylphenol)-poly(2,6-dimethylphenyl-ene oxide) (PP0-20H) [174-182] is of interest as a precursor in the synthesis of block copolymers [175] and thermally reactive oligomers [179]. The synthesis has been accomplished by five methods. The first synthetic method was the reaction of a low molecular weight PPO with one phenol chain end with 3,3, 5,5 -tetramethyl-l,4-diphenoquinone. This reaction occurred by a radical mechanism [174]. The second method was the electrophilic condensation of the phenyl chain ends of two PPO-OH molecules with formaldehyde [177,178], The third method consists of the oxidative copolymerization of 2,6-dimethylphenol with 2,2 -di(4-hydroxy-3,5-di-methylphenyl)propane [176-178]. This reaction proceeds by a radical mechanism. A fourth method was the phase transfer-catalyzed polymerization of 4-bromo-2,6-dimethylphenol in the presence of 2,2-di(4-hy-droxy-3,5-dimethylphenyl)propane [181]. This reaction proceeded by a radical-anion mechanism. The fifth method developed was the oxidative coupling polymerization of 2,6-dimethylphenol (DMP) in the presence of tetramethyl bisphenol-A (TMBPA) [Eq. (57)] [182],... 

PolyCphenylene oxide)s can also be formed by oxidative displacement of bromides from 4-bromo-2,6-dimethylphenol. Compounds, like potassium ferricyanide, lead oxide, or silver oxide, catalyze this reaction ... 

Polymerization of 3f4-dibromo-2,5-dimethylphenol (I) provided a route to polymer in which the bromine was only on the aromatic rings and not on the methyl groups (reaction 1). The reaction was found to proceed under conditions. similar to the reaction described by Staffin and Price for the polymerization of 4-bromo-2,6-dimethylphenol, III (reaction 2). Poly(3-bromo-... 

Scheme 6 Oxidative polymerization of 2,6-dimethylphenol (3) or 4-bromo-2,6-dimethylphenol...

Scheme 7 Phase-transfer catalyzed polymerization of 4-bromo-2,6-dimethylphenol (4) in the presence of (a) 2,4,6-tiimethylphenol (6) and (b) 4-tcr/-butyl-2,6-dimethylphenol (7)...

A single electron transfer mechanism seems also to best explain the synthesis of poly(thio-l,4-phenylene) from 1,4-dichlorobenzene and sodium sulfide. The mechanism of the halogen displacement phase transfer-catalyzed polycondensation of 4-bromo-2,6-dimethylphenol occurs by a single electron transfer reaction which leads to a telechelic PPO containing one bromophenyloxy and one phenolic chain end of controllable molecular weight. 

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