Biphenyldiols

Small amounts of lithium phenolate or dilithium-2,2 biphenyldiolate, whose anodic decomposition starts at about 3.2 V versus Li and thus before anodic decomposition of the borates begins, prevent the anodic decomposition of benzenediolatoborate anions in PC. The behavior of the solution is then determined by the additive. 

Lewis acids zinc chloride or aluminum chloride. Heat alone is sometimes effective, and the kinetics of the formation of dibenzofuran from 2,2 -biphenyldiol have been studied in both the presence and absence of zinc chloride. The rate and the degree of conversion are both markedly increased with increasing temperature under these conditions. ... 

Surprisingly, the 2,2 -biphenyldiol 63 (Scheme 15) is reported to produce some of the dibenzofuran 64 on methylation with methyl sulfate or iodo-methane in acetone in the presence of potassium carbonate. ... 

Similar methodology also provides a convenient synthesis of 2-dibenzo-furanol. Treatment of the 2,2 -biphenyldiol 208, (Scheme 52), readily available by oxidative coupling of 2,4-di-tcrt-butylphenol, with an excess of bromine in methanol affords the l-bromo-2-methoxydibenzofuran 209. This undergoes demethylation, debromination, and debutylation on treatment with aluminum chloride in boiling toluene and furnishes 2-dibenzofuranol (210). 

Oxidation of the 2,2 -biphenyldiol (218, Scheme 56) by one molar equivalent of lead tetraacetate affords the oxepinobenzofuran 219. With two molar equivalents of lead tetraacetate the initial product is converted to the acetate 221, which on reductive acetylation, involving oxepin-benzene oxide isomerization, affords the dibenzofuran 222. Treatment of the oxepinobenzofuran 219 with ethanolic 2,4-dinitrophenylhydrazine yields the azo compound 220. On boiling with methanol in air, compound 219 is converted to the dibenzofuranone 223, again involving valence isomerization. Reductive acetylation then affords the dibenzofuran 224. ... 

Here again the [18]crown-6 is situated on a center of symmetry with approximate D3d symmetry. Each of the centrosymmetrically related water molecules is linked to two oxygen atoms of the crown ether OH = 1.87, 1.92 A. Each end of the 4,4 -biphenyldiol units binds to a water molecule of a different crown ether. The bridging 4,4 -biphenyldiol leads to the formation of long chains. The spatial arrangement of the three constituents in the crystal are shown in Fig. 27. 

Fig. 27. A section of the crystal lattice of the [18]crown-6 4,4 -biphenyldiol diaquo 1 1 2 complex371...

CATALYTIC ASYMMETRIC EPOXIDATION OF ix,P-UNSATURATED ESTERS PROMOTED BY A YTTRIUM-BIPHENYLDIOL COMPLEX... 

Bromobiphenyl produced a major metabolite (4% of the dose) identified as either 3-bromo-4-biphenylol or 5-bromo-2-biphenylol a minor dihydroxylated metabolite was also detected. 4-Bromobiphenyl yielded two metabolites 4 -bromo-4-biphenylol (2% of the dose) and 4 -bromo-3,4-biphenyldiol (1.5% of the dose). Experiments witli tritiated 4-bromobiphenyl suggest that the metabolism of this congener involves the formation of an arene oxide. 

Similar results have been reported in rats (Sparling et al. 1980). 4 -Bromo-4-biphenylol was the major metabolite of 4-bromobiphenyl. 2-Bromobiphenyl was metabolized to 2-bromo-4,4 -biphenyldiol and... 

With Chiral DiolTTi Complexes Harada investigated the influence of the torsional angles of biaryl rings on the enantioselecdvity in the asymmetric Diels-Alder reaction of cyclopentadiene with methyl acrylate catalyzed by a series of Ti complexes possessing chiral 2,2 -biaryldiols. The best results were obtained by the use of chiral binaphthol or 6,6 -hexylenedioxy-2,2 -biphenyldiol [52] (Eq. 8A.29). 

A catalytic asymmetric epoxidation reaction of a,/l-unsaturated esters via conjugate addition of an oxidant using chiral yttrium-biphenyldiol-Ph3As=0 complexes has been developed. Yields up to 90% and ees up to 99% have been achieved.43... 

The chiral auxiliary in the diaryls 164 can be selectively removed to give (A)-biphenyldiols 165 in high enantiomeric purities and high yield (Equation 36) <2000JOC1335>. 

A chiral version of 16 (alkylidene 17), containing a biphenyldiolate ligand, is effective in producing metathesis products that exhibit high yields and excellent % ee values under mild conditions (equation 11,12).27... 

Other use of the functionalized chiral BINOL includes the 5,5, 6,6, 7, 7, 8,8 -octahydro derivative developed by Chan and coworkers, the titanium complex of which is more effective than BINOL in the enantioselective addition of triethylaluminum and diethylzinc a 4,4, 6,6 -tetrakis(perfluorooctyl) BINOL ligand developed for easy separation of the product and catalyst using fluorous solvents for the same zinc reaction an aluminum complex of 6,6 -disubstituted-2,2 -biphenyldiols used by Harada and coworkers in the asymmetric Diels-Alder reaction a titanium complex of (5 )-5,5, 6,6, 7,7, 8,8 -octafluoro BINOL employed by Yudin and coworkers in the diethylzinc addition, in the presence of which the reaction of the enantiomeric (/f)-BINOL is promoted . 

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