Biphenyls New Aryl Radical Sources

5 Gomberg-Bachmann Reactions 5.1 Biphenyls New Aryl Radical Sources 

Since phenols can act as hydrogen donors, the use of polar solvents stabilizing the phenolic hydrogen by hydrogen bonding is beneficial. Other than with phenolates, efficient chain reactions have so far only been observed with reactive phenols such as 1,4-hydroquinone. In all other cases, catalytic amounts of the reductant proved insufficient to achieve clean conversions. As with 4-substituted phenolates, comparably good regioselectivities can be achieved with 4-substituted phenols. 

Due to their high solubility in acidic aqueous solutions, 4-aminophenols, tyramines, and tyrosine derivatives are well-suited substrates for this type of arylation reactions [154]. 

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