Synthesis of octabrominated diphenyl ethers from aminodiphenyl ethers

Polybrominated diphenyl ethers (PBDEs) are additive brominated flame retardants (BFRs), which have become widespread pollutants in abiotic and biotic environments including man. Tetra- to hexaBDEs and decaBDE are the most common environmental PBDE contaminants. Congeners of octabromodiphenyl ethers (octaBDEs) originate from used industrial OctaBDE mixtures and from transformation products of the high-volume industrial BFR mixture "DecaBDE", which most exclusively consists of perbrominated diphenyl ether (BDE-209). The objective of the present work was to develop methods for the synthesis of authentic octaBDE congeners in order to make them available as standards for analytical, toxicological, and stability studies, as well as studies concerning physical-chemical properties. The syntheses of six octaBDEs, 2,2',3,3',4,4',5,5'-octabromodiphenyl ether (BDE-194), 2,2',3,3',4,4',5,6'-octabromodiphenyl ether (BDE-196), 2,2',3,3',4,5,5',6-octabromodiphenyl ether (BDE-198), 2,2',3,3',4,5',6,6'-octabromodiphenyl ether (BDE-201), 2,2',3,3',5,5',6,6'-octabromodiphenyl ether (BDE-202), and 2,2',3,4,4',5,6,6'-octabromdipheny ether (BDE-204), are described, of which BDE-204 was prepared via two different pathways. Syntheses of BDE-198, BDE-201, BDE-202, and BDE-204 are based on octabromination of mono- or diaminodiphenyl ethers followed by diazotization and reduction of the amino group(s). BDE-194 and BDE-196 were prepared by bromination of 3,3',4,4',5,5'-hexabromodiphenyl ether (BDE-169) and 2,3,3',4,4',5',6-heptabromodiphenyl ether (BDE-191), respectively, and BDE-169 and BDE-191 were prepared from 4,4'-diaminodiphenyl ether and 3,4'-diamiodiphenyl ether, respectively. The synthesized PBDE congeners are described by 1H NMR, 13C NMR, electron ionization mass spectra, and their melting points.