14400-94-3

A mild, green and highly efficient protocol was developed for the synthesis of substituted phenols via ipso-hydroxylation of arylboronic acids in ethanol. The method utilizes the combination of aqueous hydrogen peroxide as the oxidant and H2O2/HBr as the reagent under unprecedentedly simple and convenient conditions. A wide range of arylboronic acids were smoothly transformed into substituted phenols in very good to excellent yields without chromatographic purification. The reaction is scalable up to at least 5 grams at room temperature with one-minute reaction time and can be combined in a one-pot sequence with bromination and Pd-catalyzed cross-coupling to generate more diverse, highly substituted phenols.

Four new difluorinated tetra- and pentabromo BDE internal standards for GC-MS/GC-ECD analysis, 2F-BDE 47, 2F-BDE 85, 2F-BDE 99 and 2F-BDE 119, have been prepared in 98-99.0% purity, mainly by coupling of the new tribromodifluorophenols (19-21) and symmetr

A growing number of studies have reported phenolic halogenated compounds (PHCs) that are retained in the blood of humans and wildlife. These PHCs may be industrial chemicals; metabolites thereof, as in the case with polychlorobiphenylols (OH-PCBs); or of natural origin. The present study was aimed to identify hitherto unknown PHCs in human plasma with chemical structures that are consistent to PHCs known to possess endocrine-disrupting activity. For this purpose, samples of blood plasma from 10 randomly selected male blood donors from Sweden were pooled and analyzed by GC/ECD and GC/MS. Brominated, bromochlorinated, and chlorinated methyl derivatives of phenols and OH-PCBs were synthesized to be used as authentic reference standards. More than 100 PHCs were indicated in the plasma, and among those a total of 9 monocyclic brominated or chlorinated phenol-, guaiacol-, and/or catechol-type compounds were identified as their methylated derivatives. The two major compounds were 2,4,6-tribromophenol and pentachlorophenol. Thirty-eight OH-PCB congeners were structurally identified on two GC columns of different polarity. The origin of the OH-PCB metabolites in the context of their parent PCB congeners are suggested. Other PHCs identified in the male plasma were Triclosan (5-chloro-2-[2,4-dichlorophenoxy] phenol), a common bactericide; 4-hydroxy-heptachlorostyrene, a metabolite of octachlorostyrene; and 3,5-dibromo-2-(2,4-dibromophenoxy)phenol, a natural compound and a potential metabolite of polybrominated diphenyl ethers.

Polybrominated diphenyl ethers (PBDEs) have become widely distributed as environmental contaminants due to their use as flame retardants. Their structural similarity to other halogenated aromatic pollutants has led to speculation that they might share toxicological properties such as hepatic enzyme induction. In this work we synthesized a number of PBDE congeners, studied their affinity for rat hepatic Ah receptor through competitive binding assays, and determined their ability to induce hepatic cytochrome P-450 enzymes by means of EROD (ethoxyre-sorufin-O-deethylase) assays in human, rat, chick, and rainbow trout cells. Both pure PBDE congeners and commercial PBDE mixtures had Ah receptor binding affinities 10-2-10-5 times that of 2,3,7,8-tetrachlorodibenzo-p-dioxin. In contrast with polychlorinated biphenyls, Ah receptor binding affinities of PBDEs could not be related to the planarity of the molecule, possibly because the large size of the bromine atoms expands the Ah receptor's binding site. EROD activities of the PBDE congeners followed a similar rank order in all cells. Some congeners, notably PBDE 85, did not follow the usual trend in which strength of Ah receptor binding affinity paralleled P-450 induction potency. Use of the gel retardation assay with a synthetic oligonucleotide indicated that in these cases the liganded Ah receptor failed to bind to the DNA recognition sequence.

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