Biphenyls ortho-substituted

Scott et al. [45] prepared diimine derivatives of 2,2 -diamino-6,6 -dimethyl-biphenyl (as structure 37 in Scheme 19) as copper chelates for the catalyzed cyclopropanation reaction. All catalysts were active in this reaction but enan-tioselectivities varied importantly according to the substitution pattern of the imine aryl group only ortho-substituted ligands (by chloride or methyl groups) led to products with measurable enantioselectivity for the model test reaction (up to 57% ee with 37). 

The use of oxazolines in aromatic substitution is a valuable synthetic tool.2 The o-methoxy- or o-fluorophenyloxazoline reacts readily with a variety of organofithium or Grignard reagents to displace only the ortho substituent. In this fashion a number of ortho-substituted benzoic acids, benzaldehydes, and unsymmetrical biphenyls are accessible. The reaction takes place under very mild conditions, usually at or below room temperature, and thus allows a number of other sensitive groups to be present. 

Kristofferson A, Voie AOA, Funnum F. 2002. Ortho-substituted polybrominated biphenyls activate resiratory burst in granulocytes from humans. Toxicol Lett 24(1-2) 161-166. 

In situ reductive dechlorination has been cited as an important pathway for biochemical weathering of PCBs in sediments (2, 5). The reductive dechlorination hypothesis is based on the premise that microbial action on PCB congeners is sterically selective for the chlorines in the meta and para positions on the biphenyl rings (i.e., 3, 3, 4, 4, 5, and/or 5 ). Such selectivity would result in the cleaving of the chlorines in these positions (5). If this process occurs, the terminal dechlorination products of the microbially resistant ortho-substituted congeners in the anaerobic environment should be 2,2 -DCB, 2,6-DCB, 2,2, 6-TrCB, and 2,2, 6,6 -TCB. Thus, the weight... 

Coristine, S., Haffner, G.D., Ciborowski, J.J.H., Lazar, R., Nanni, M.E., Metcalfe, C.D. (1996) Elimination rates of selected di-ortho, mono-ortho, and non-ortho substituted polychlorinated biphenyls in rainbow trout (Oncorhynchus mykiss), Environ. Toxicol. Chem. 15, 1382-1387. 

Hong, C.-S., Qiao, H. (1995) Generator column determination of aqueous solubilities for non-ortho and mono-ortho substituted polychlorinated biphenyls. Chemosphere 31, 4549 1557. 

Patterson Jr. DG, Todd GD, Turner WE, et al. 1994. Levels of non-ortho-substituted (coplanar), mono-and di-ortho-substituted polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans in human serum and adipose tissue. Environ Health Perspect 102(supp 1) 195-204. 

In a recent paper, the same authors showed that iron(III) chloride can mediate the oxidative coupling of substituted aryl ethers with an observed regioselectivity that depends on the substitution pattern [66] meta-substituted phenol ethers 77 led to polymers (Scheme 18a) whereas para-substituted phenol ether 79 gave predominantly biphenyl structures (Scheme 18b). ortho-Substituted phenol ether 81 provided a dimer with the Ar-Ar bond at a position para to one of the methoxy substituents (Scheme 18c). 

Ortho-substituted biphenyls also do not possess a stereogenic centre, but exist as stable enantiomers if (a) the substituents are large enough and (b) the ortho sites on each ring contain different substituents. 

Lindner AS, Whitfield C, Chen N, Semrau JD, Adriaens P. Quantitative structure-biodegradation relationships for ortho-substituted biphenyl compounds oxidized by Methylosinus trichosporium OB3b. Environ Toxicol Chem 2003 22 2251-7. 

Gooch, J.W., A.A. Elskus, P.J. Kloepper-Sams, M.E. Hahn and J.J. Stegeman. Effects of ortho and non-ortho substituted polychlorinated biphenyl congeners on the hepatic monooxygenase system in scup (Stenotomus chrysops). Toxicol. Appl. Pharmacol. 98 422-433, 1989. 

Gutjahr-Gobell, R.E., D.E. Black, L.J. Mills, R.J. Pruell, B.K. Taplin and S. Jayaraman. Feeding the mummichog (Fundulus heteroclitus) a diet spiked with non-ortho and mono-ortho-substituted polychlorinated biphenyls accumulation and effects. Environ. Toxicol. Chem. 18 699—707, 1999. 

Bohm V, Schulte E, Thier H-P. 1993. Polychlorinated biphenyl residues in food and human milk Determination of co-planar and vaono-ortho substituted congeners. Z Lebensm Unters Forsch 196(5) 435-440. 

Eriksson P, Fredriksson A. 1996a. Developmental neurotoxicity of four ortho-substituted polychlorinated biphenyls in the neonatal mouse. Environ Toxicol Pharmacol 1(3) 155-165. 

Hebert CE, Gamberg M, Elkin BT, et al. 1996. Polychlorinated dibenzodioxins, dibenzofurans and non-ortho substituted polychlorinated biphenyls in caribou (rangifer tarandus) from the Canadian Arctic. Sci Total Environ 183(3) 195-204. 

Hong CS, Xiao J, Casey AC, et al. 1994. Mono-ortho- and non-ortho substituted polychlorinated biphenyls in human milk from Mohawk and control women Effects of maternal factors and previous lactation. Arch Environ Contam Toxicol 27 431 37. 

Patterson DG Jr., Lapeza CR, Barnhart ER, et al. 1989. Gas chromatographic/mass spectrometric analysis of human serum for non-ortho (coplanar) and ortho substituted polychlorinated biphenyls using isotope-dilution mass spectrometry. Chemosphere 19 127-134. 

Dibenzodioxin may be substituted with chlorine in 75 different ways, and dibenzofurans in 135 different ways. The toxicity, as well as the environmental stability of the 210 derivatives, varies extremely. There are 209 possible chlorinated biphenyls, but only those with one or no chlorines in the ortho position have a mode of action similar to that of TCDD. (The ortho-substituted PCBs may also be toxic, but then through other mechanisms.)... 

Fuoco R, Colombini MP, Samcova E (1993) Individual determination of ortho-and non-ortho substituted polychlorinated biphenyls (PCBs) in sediments by high performance liquid chromatographic pre-separation and gas chromatography - ECD detection. Chromatographia 36, 65-70. 

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