Migratory aptitude of the triphenylgermyl group in sterically hindered phenols and phenoxyl radicals
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The phenoxyl radicals generated by oxidation of 2-trimethylsilyl-4-tert-butyl-6-triphenylgermylphenol with potassium ferricyanide rearrange by migration of the trimethylsilyl group to the oxygen and dimerize, forming substituted bis(siloxy)biphenyls. The migratory aptitude of the groups in the phenoxyl radicals decreases in the order GeMe3>SiMe3> SiPh3 ≈ GePh3.
Two types of reaction take place in the phenoxyl radical derived by one-electron oxidation of 2-triphenylsilyl-4-tert-butyl-6-triphenylgermylphenol, firstly, migration of the Ph3Ge and Ph3Si groups to the oxygen and C-C dimerization to form a bis(siloxy)biphenyl and a bis(germyloxy)biphenyl, and secondly C-O dimerization of the phenoxyls to form a quinol ether, where both heteroorganic groups remain attached to the ring.
2-Trimethylsilyl-4-tert-butyl-6-triphenylgermylphenol (I) and 2-triphenylsilyl-4-tert-butyl-6-triphenylgermylphenol (II) isomerize at 200°C to aryloxysilanes and germanes; phenol (I) forms mainly the aryloxysilane and phenol (II) the aryloxygermane.
KeywordsOxidation Oxygen Ether Potassium Migration
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