cas 59261-08-4, 2,2',4,4',6,6'-HEXABROMOBIPHENYL

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Asymmetric bromine-lithium exchange: Application toward the synthesis of natural product
Asymmetric bromine-lithium exchange has been successfully employed to synthesize bicoumarin chiral building blocks of (+)-isokotanin A and (-)-kotanin in good yields and with an excellent level of enantioselectivity. This is the first reported example of formal syntheses, using this direct methodology, leading to the single (M)-atropoisomer of (+)-isokotanin A and (-)-kotanin building blocks, without any resolution step.
Graff, Julien,Debande, Thibaut,Praz, Jezabel,Guenee, Laure,Alexakis, Alexandre
supporting information
p. 4270 - 4273
(2013/09/12)

Catalytic asymmetric bromine-lithium exchange: A new tool to build axial chirality
We present here the first catalytic desymmetrization of the 2,2′,6,6′-tetrabromobiphenyl 1 and analogues, by a bromine-lithium exchange catalyzed by either diamines or diether derivatives (0.5 equiv.), yielding axially chiral compounds in high yield (up to 89%) and high enantioselectivity (up to 82%).
Perron, Quentin,Alexakis, Alexandre
supporting information; experimental part
p. 2611 - 2620
(2011/01/05)

Anaerobic transformation of polybrominated biphenyls with the goal of identifying unknown hexabromobiphenyls in Baltic cod liver
Polybrominated biphenyls (PBBs) have been introduced as flame retardants in 1970. Despite decreasing application rates since the mid-1970s, PBB residues are still reported in the environment. Furthermore, environmental PBB residues often do not match the PBB pattern in technical products. To get insights into the structures of environmentally-relevant PBBs, the congener patterns of technical hexabromobiphenyl (THBB), octabromobiphenyl (TOBB), synthesized PBB 209 were compared to PBB residues in a cod liver sample from the Baltic Sea. The most relevant PBB congeners in Baltic cod liver were not present in the technical products and therefore most likely metabolites. For this reason, TOBB and HPLC-fractions obtained from this technical product were incubated with super-reduced cyanocobalamine. Reductive debromination was found to be the predominant transformation process. Bromine substituents in ortho-positions proved to be more recalcitrant, and several of the unknown PBBs were tri- and tetra-ortho substituted congeners. Furthermore, the key-PBBs determined in Baltic cod liver were formed during this process. The most important hexabromobiphenyl in Baltic cod liver was identified as PBB 155 by parallel synthesis. PBB 155 which was not detected in the technical PBB product analyzed was suggested as an indicator PBB congener suited to decide whether PBB residues originate from the previous use of THBB (low relative abundance of PBB 155) or TOBB/TDBB (high relative abundance of PBB 155). The latter scenario was found to be valid for the Baltic cod liver sample. Thus, PBBs in the Baltic Sea appeared to originate from partially-weathered residues of PBB 209.
von der Recke, Roland,Vetter, Walter
p. 352 - 359
(2008/09/21)

Structural Studies of Some 2,6(2',6')-Halogen-Substituted Biphenyl Derivatives
Single-crystal X-ray structure determinations have been carried out at 295 K on a number of biphenylderivatives substituted with chlorine or bromine in the 2- and 6-positions in order to ascertain the effect of substitution on the torsion angle about the central bond. 2,2',6,6'-Tetrachlorobiphenyl, (1), is orthorhombic, P nca, a 12.35(1), b 10.521(7), c 9.390(8) Angstroem, Z 4; the structure was refined to a residual of R 0.040 for No 528 independent 'observed' reflections.The interplanar dihedral angle, θ, is 81.7 deg. 4'-Bromo-2,4,6-trichlorobiphenyl, (2), is monoclinic, C2/c, a 19.27(1), b 7.940(2), c 33.315(8) Angstroem, β 90.93(6) deg, Z 16; R 0.036 for No 1795 with θ 84.3 and 80.6 deg for the two independent molecules. 2,2',4,4',6,6'-Hexabromobiphenyl, (3), is orthorhombic, P nca, a 14.48(1), b 12.71(1), c 8.534(7) Angstroem; R 0.044 for No 693 with θ 83.0 deg. 2,4,4',6-Tetrabromobiphenyl, (4), is triclinic, P1, with a 8.14(1), b 10.74(2), c 35.42(4) Angstroem, α 87.87(10), β 79.39(10) deg, Z 8; R 0.049 for No 3962, with θ 89.8, 80.7, 86.9, 83.6 deg, for the four independent molecules.Steric interactions between the substituents ortho to the central inter-ring bond are not the sole determinant of the geometry of these compounds in the solid state.The pairs (1) and (3), and (2) and (4), are pseudoisostructural in each case.
Field, Leslie D.,Skelton, Brian W.,Sternhell, Sever,White, Allan H.
p. 391 - 399
(2007/10/02)