Rapid halogen substitution and dibenzodioxin formation during tyrosinase-catalyzed oxidation of 4-halocatechols.

4-Fluoro-1,2-benzoquinone, generated by tyrosinase oxidation of 4-fluorocatechol in aqueous buffer, rapidly undergoes substitution by O-nucleophiles (water or catechols) with release of fluoride. 4-Chloro- and 4-bromocatechol behave similarly. The reactions, which have toxicological implications, have been monitored by spectrophotometry and HPLC/MS, and intermediate and final products, including dibenzodioxins, identified.