O-Amino-biphenyl

A solution of o-biphenyl diazonium sulfate is prepared as follows o-amino-biphenyl 21.1 g (0.125 mole), is dissolved by warming in a mixture of 100 ml of glacial acid and 136 ml of water. To this solution is added a mixture 11.2 ml of concentrated sulfuric acid and 25 ml of water. The temperature is then lowered to 0° to 5°C and 8.65 g (0.125 mole) of sodium nitrite is added in small portions to the stirred solution over a one hour period. The solution is stirred for an additional two hours at 0° to 5°C after the addition of the nitrite is complete. 

Pictet-Hubert reaction. Phenanthridine cychzation by dehydrative ring closure of acyl-o-amino-biphenyls on heating with zinc chloride at 250-300C or with phosphorus oxychloride in boiling nitrobenzene. 

Carbon disulfide is competitive with CCI4 in transparency, but even less desirable from a health standpoint. In addition, it offers a great fire and explosion hazard. Its use should be considered only when it provides a real advantage e.g., Whetsel et al. claim a lowering of the detection limit for primary aromatic amines in secondary aromatic amines when CS2 is used instead of CCI4. Before using CS2 as a solvent for amines, one should determine whether it will react with the solute e,g, o-amino-biphenyl reacts almost quantitatively with CS2, presumably forming a thiocarbonic acid. 

The most common methods of C—B—X ring construction employ hydroboration/amination, aminolysis of 4-bromoalkylborinate esters, electrophilic additions of boron halides to o-amino-styrenes and -biphenyls, insertion of hydrazines into 1,2,5-thiadiborolenes, and aldol-type condensations. Specific examples of these processes are presented in the following sections 6.28.3.1 and... 

It has been considered that a coordinated nitrene may give the same reaction and work in our group has shown that this is indeed possible in at least one case [260] (see also Chapter 5). However, it should be also noted that we now know that most reactions of nitro- and nitroso compounds with a metal complex occur through an intermediate electron transfer to the organic compound vide supra). Thus the formation of the radical anion of o-nitro- and/or o-nitrosobiphenyl should be considered as probable during the reaction. The reactivity of such radicals is virtually unknown and it cannot be excluded that these species, and not a nitrene intermediate, are responsible for the carbazole formation. The validity of carbazole formation as an indication for nitrene intermediates has been questioned very early [261]. It was shown that other reactions (including oxidation of 2-amino-biphenyl) can afford carbazole. Thus the results of this test should be taken with caution. 

Adejare, A. Miller, D. D. Synthesis of fluorinated biphenyls via aryne reaction. Tetrahedron Lett. 1984, 25, 5597-5598. Skowronska-Ptasinska, M. Verboom, W. Reinhoudt, D. N. Effect of different dialkyl-amino groups on the regioselectivity of lithiation of O-protected 3-(dialkylamino)phenols. 

A methyl group ortho to each of the amino groups in benzidine again exerts a definite effect in favor of ether formation, for, whereas benzidine gives only biphenyl, o-tolidine yields approximately equal quantities of ether and hydrocarbon.14... 

Fig. 7.7. Some of the covalent links which occur in structural proteins. ABCD represents one protein, EFB C G another. The N-terminal amino acid A is linked to an o-quinone which is also linked to a lysyl residue F(=quinone tanning) BB represents two tyrosyl residues coupled by a biphenyl linkage CC represents two cysteinyl residues coupled by a cystine linkage (as in keratin) D, E and G are not cross-linked. (After Brunet, 1967.)...

It is not strictly necessary to introduce the 1,1 -binaphthyl backbone. For axial chirality, the biphenyl scaffold is sufficient, provided that rotation around the phenyl-phenyl axis is sufficiently hindered. Hoveyda combined this reduced axial chiral motif with additional central chirality in the imidazole backbone (O and C ) [6,7], Synthetically, the task is accomplished by Buchwald-Hartwig amination of enantiomerically pure (H ,21 )-diphenylethylenediamine with 1-methoxy-I -iodo-biphenyl and subsequent reaction with mesityl bromide to introduce the bulky wingtip group on the second amino group of the chiral starting material. Ring closure reaction with triethyl orthoformate and hydrolysis of... 

One-electron oxidation of aromatic compounds (ArH) leads primarily to corresponding radical cation which exist either in monomeric (ArH +) or dimeric form [(ArH)2 ] the latter usually formulated as r-dimer [70]. However, radical cations are reactive species and can undergo further reaction yielding more persistent radical cations e.g. oxidation of rert-butylbenzene or of toluene or o-xylene yielded radical cation of 4,4 -di-rerf-butyl biphenyl, 4,4 -bitoluene or 3,3, 4,4 -tetramethyl biphenyls, products of further a-coupling, proton loss and further one-electron oxidation [71]. This is a well-known pathway of biaryl dehydrodimerization, explored in anodic and metal-ion oxidation of ArH [72, 73]. Other compounds with high reactivity in (T-coupling are alkoxy and amino substituted ArH [73]. Thus a risk with characterization of radical cations is that hardy survivors and not primary radical... 

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