O-biphenols

Palladium may also show exceptional selectivities. as in the conversion of o,o -biphenol to o-(2-hydroxycyclohexyl)phenol (55), or p-phenylphenol to p-cyclohexylphenol (90%). If this latter reduction is continued in methanol solvent, the main product is not 4-cyclohexylcyclohexanol, but rather 4 cyclohexylcyclohexyl methyl ether (84%) (5d). 

Dihydroxybiphenyl CAS 1806-29-7 EINECS/ELINCS 217-303-0 Synonyms 2,2 -Biphenol o,o -Biphenol [1,1 -Biphenyl]-2,2 -diol 2,2 -Biphenyldiol Biphenyl-2,2 -diol... 

Gevorgyan and co-workers reported a mild, practical, and efficient method for the synthesis of symmetrical and unsymmetrical o-biphenols, o-phenol-naphthols, and o-binaphthols. The method involves a Pd-catalyzed intramolecular C-H aiylation of unsymmetrical bis-aiylo)q silanes to give the seven-membered oxasilacycles, which, via a consecutive routine TBAF deprotection, furnish valuable unsymmetrical o-biphenols and o-binaphthols. In 2013, the intramolecular cyclization of di-ortAo-bromoaiylo q acetal and o/tfto-bromoaiylo y acetal to the corresponding dibenzo[l,3]dioxepines was developed. ... 

Several other minor metabolites of phenol have been identified in vitro. The formation of 1,4-dihydroxybenzene and 1,2-dihydroxybenzene in a 20 1 molar ratio was observed in isolated rat liver microsomes incubated with phenol (Sawahata and Neal 1983). Further catalysis to / -benzoquinone, 4,4 -biphenol, and biphenoquinone has been demonstrated in microsomes and in in vitro peroxidase preparations. The benzoquinone products react nonenzymatically with nucleophiles, including cysteine and reduced glutathione, to yield. V-conjugates of 1,4-dihydroxybenzene and 4,4-biphenol (Eastmond et al. 1986 Lunte and Kissinger 1983 Subrahmanyam and O Brien 1985). 

Phenols act as acids toward [ (tmpa)Cu 2(02)]2+ (3) and Cu2(XYL—O—)(02)] + (8), hydronating them to give hydrogen peroxide and phenoxo-copper(II) complexes. However, hydrogen-atom abstraction takes place when complex [Cu2(N4)(02)]2+ (15) is reacted with phenols, giving phenoxy radicals that dimerize to produce biphenols or diphenoquinones, depending on the position of the substituents on the phenols. This shows that 15 is a better one-electron oxidant than 3 or 8. 

Do stands for neutral donor sites like terminal -OR or -NR2 and internal -O- or -NR- groups, respectively. However, multiply charged ligands like the doubly charged or divalent catechol and biphenol are also considered as functionalized ligands. 

With heterogeneous Pd/C catalyst, CU2O showed superior performance in oxidative carbonylation of phenols [29]. However, copper ICCs promote side reactions such as phenol oxidation by oxygen to form 2,2-biphenol [16] or formation of o-phenylene carbonate [51]. 

So far we have seen the reactions of chlorocyclophosphazenes with reagents that may be termed monofunctional. For example, a phenol in its reactions with chlorocyclophosphazenes will react as a nucleophile and form N3P3(OPh)6 containing P-0 linkages. If instead of a phenol we used a biphenol we will have two sites that can react with the phosphorus centers. In this manner there are several difunctional reagents such as diamines (ethylenediamine, 1,3-diaminopropane, phenylenediamine), diols (ethyleneglycol, 1,3-propanediol, catechol), and amino alcohols (ethanolamine, propanolamine, o-aminophenol) [2,15]. 

Figure 9 ICD spectra of complexes between bisphenol host 11 (6.83 X 10 M) and chiral diamine guest 12 (1.37 x 10 M). (Reprinted from Tetrahedron Lett., 38, T. Mizutani, H. Takagi, O. Kara, et ah, Axial chirality induction in flexible biphenols by hydrogen bonding and steric interactions, 1991, Cop)night (1997), with permission from Elsevier.)...

Now the most important Route la will be illustrated by means of the synthesis of BIPHEPHOS (Scheme 2.89) [7]. The required biphenyl phosphorchloridite can be prepared by the reaction of PCI3 with 2,2 -dihydroxybiphenol in the presence of NEtj, as suggested by the Amsterdam group [78]. Alternatively, the reaction can be conducted in a suspension of toluene in the absence of a base, under the condition that HCl is removed under vacuum [79]. The chlorophosphite is used in the second step for the condensation reaction with the substituted biphenol in the presence of pyridine. Final crystallization from acetonitrile produces the desired product. Care should be taken with traces of chlorine or acetonitrile, which affects the longterm stability of the diphosphite [80]. These contaminations can be removed by recrystallization, for example, from o-xylene, n-heptane, or ethyl acetate, or by washing with acetone. 

It is still not clear which structural features favor the formation of the symmetric or the nonsymmetric diphosphite. Apparently, steric reasons in the intermediate may facilitate transesterification. For instance, transesterification was observed in the reaction of biphenol phosphorchloridite with o-phthaUc acid, whereas with phthalic anhydride only the corresponding pyrophosphite was produced (Scheme 2.95) [84]. Synthesis of a targeted diphosphite could be achieved only with w-phthalic acid (D. Selent and A. Borner, unpublished results). 

Ti(IV) monosuhstituted Keggin-type polyoxometalates (Ti-POMs) are stable towards the hydrolysis of Ti-O-W bonds and oxidative degradation. The catalytic oxidation of 3 using H2O2 as the oxidant over Ti-POMs yields 2,3,5-TMHQ (1) and the biphenol (6) as main products (Fig. 16.6). The product distribution depends significantly on the TMP/Ti-POM molar ratio. ... 

A. Linear polymers We have synthesized poly(ether ketone)s 19 by condensation of 1,2-dibenzoylbenzenes 18 with various biphenols. These o-substituted poly(ether ketone)s, as expected, are amorphous materials. We have synthesized polymers with 0,2 and 4 pendant phenyl groups on the central ring. ... 

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