4,4 -Dihydroxybiphenyl, reaction with

The mild, water-soluble Lewis acid, indium(III) chloride is finding increasing use in organic synthesis, including heterocyclic syntheses. An indium(III) chloride catalysed synthesis of a range of new dlbenzo[(f,/ [l,3]dioxepines 125 has been described based on the reaction of 2,2 -dihydroxybiphenyl 124 with ketones or P-keto esters capable of enolisation yields of the products 125 were low to moderate <04TL6909>. 

H0)2As=0 rather than an intermediate complex, as found for the reaction with chromic acid. Cyclic esters, e.g. (134), can be obtained from arsenic trichloride and 2,2 -dihydroxybiphenyl, and when the reaction with pyro-... 

The oxidative dimerization of dialkylphenols proceeds in the presence of immobilized Cu(Il) complexes. One-electron reduction of the Cu(II)-phenolate formed results in the production of a phenoxy radical which is oxidized via the intermediate dihydroxybiphenyl to diphenoquinone. At the same time the active centers are regenerated by oxidation of the Cu(I) formed to Cu(II) (the ping-pong mechanism). Such cycles - reduction of metal ions at the stage of the reaction with the substrate and its reoxidation by molecular oxygen - are often observed. 

Spiran products similar to (7.345a) result from reactions with 2,3 dihydroxynaphthalene (7.345d), and 2,2 dihydroxybiphenyl (7.345c). Imine analogues can be synthesised by reaction with an appropriate compound containing adjacentamine groups. 

Reaction of 4,4 -dihydroxybiphenyl 18, with EAA and InCl3 as a catalyst affords a mixture of coumarins 19 and 20 (Scheme 12) (12T8683). 

We have recently demonstrated a convenient and selective synthesis of a series of hydroxy [l ]metabiphenylophanes with three and four biarene units 2 involving base-catalyzed condensation of 5,5 -di-te/t-butyl-2,2 -dihydroxybiphenyl (1) with formaldehyde under refluxing xylene, and we have reported their unique properties [15]. The cyclic trimer 2b was obtained as a major product with NaOH as base in xylene, while the action of the larger Cs" led to the larger macrocyclic tetramer 2c. These results seem to indicate that the template effect of an alkali metal cation plays an important role in this condensation reaction as previously observed in the preparation of calixarenes [6]. 

Other polymers have been reported from the reactions of N3P3CI6 with alkoxyboron compounds, the sodium salt of hydroquinone, and 4,4 -dihydroxybiphenyl. ... 

The ring-closure (cyclodehydration) of dihydroxy compounds affords five-, six-, seven-, and eight-membered cyclic ethers. The reaction can efficiently and conveniently be carried out with Nafion-H.687,688 Even diphenols (2,2 -dihydroxybiphenyls) undergo dehydration to afford oxolane derivatives276 [Eq. (5.244)]. The low yields of the fc/T-butyI-substituted compounds result from trans-terf-butylation (see Section 5.2.6). Cyclodehydration of stereoisomeric... 

This monophasic biotransformation system was used for the hydroxylation of 2,2 -dihydroxybiphenyl to 2,2, 3-trihydroxybiphenyI within a reaction time of 2.5 h and 2.2. 3,3 -tetrahydroxybiphenyl after 23 h. A mean volume productivity of 0.43 and 0.05 g l-1 h 1, respectively, was achieved for these biotransformations. Furthermore, HbpA and FDH were applied in 80 vol.% decanol to hydroxylate 2-hydroxybiphenyl to 2,3-dihydroxybiphenyl with a productivity of 0.46 g 1 1 h 1 and a total turnover number of 503. In 10 vol.% aqueous methanol the total turnover number of 30 and enzyme stability for at least 60 h were observed. Because of the... 

The reaction of N3P3C16 with catechol (8), 2,3-dihydroxynaphthalene (11), 1,8-dihydroxynaphthalene (17), 2,2-dihydroxybiphenyl (11), and several aliphatic diols (21, 399) gives spirocyclic derivatives. A typical example is... 

Reaction between phenol and hydroxyl yields the dihydroxybenzenes, which can then undergo further oxidation (hydroquinone to benzoquinone, further hydroxylated to hydroxybenzoquinone, catechol and resorcinol to trihydroxybenzenes [79,100]). The condensation products, phenoxyphenols and dihydroxybiphenyls, most likely originate from the reaction between phenol and the phenoxyl radical [101]. Their presence indicates that some phenoxyl forms in the system, due to the reaction of phenol with OH or NO2. The possibility for NO2 to oxidise phenol to phenoxyl has been the object of a literature debate [102,103] in the context of nitration processes. The problem can be tackled upon consideration of the reduction potentials of the various species. The reduction potential of phenoxyl to undissociated phenol is E = 1.34 V - 0.059 pH [104], while for the reduction of nitrogen dioxide to nitrite it is E = 0.90 V [105]. Accordingly oxidation of phenol to phenoxyl would be possible above pH 7.5, and of course in the presence of phenolate (pH > 10 [106]). 

Stirring diorgano tellurium diethoxides in a diethyl ether/pentane medium with the stoichiometrically required amounts of 1,2-dihydroxyethane, 1,3-dihydroxypropane, 2-hydroxyphenylmethanol, 1,2-dihydroxybenzene, 2,2 -dihydroxybiphenyl, 2,3-dihydroxy-naphthalene, or 4-methylphenol produced diorgano tellurium alkoxides and phenoxides. These compounds precipitated as white solids from the reaction mixtures or separated as oils that crystallized during storage at low temperatures. The products of the transesterification with diols could be oligomeric. The low solubility of these compounds prevented the determination of their molecular masses . 

A charge transfer complex is involved in the photochemical reaction between 4-cresol and tetranitromethane. Irradiation at 350 nm yields the o-nitrated product 235 ° . Other phenols such as phenol, 2- and 4-chlorophenol and 2- and 4-cresol behave in a similar manner and irradiation yields 2- and 4-nitrated products (236, 237) ° . The quantum yields for product formation are in the range 0.12-0.31. Only the formation of 3-nitrophenol from phenol is inhibited, as might be expected from attack at the 3-position, and shows a low quantum yield. It has been reported that 2-hydroxy- or 4-hydroxybiphenyl and 4,4 -dihydroxybiphenyl are the primary products formed from the photochemical reaction of biphenyl with sodium nitrate in aqueous methanol . Apparently the hydroxybiphenyls are prone to undergo photochemical nitration as a secondary process and yield the biphenyls 238 and 239 as well as 4,4 -dihydroxy-3,3 -dinitrobiphenyl, originally reported by Suzuki and coworkers under heterogeneous conditions. 

As with polystyrene sulfonic resins, Nafion-based acid catalysts are highly efficient for hydration and dehydration processes and, in general, for condensation reactions that occur with the formation of water or similar secondary products. Formation of ethers has been studied for various alcohols [109-111]. Dehydration of 1,4- and 1,5-diols at 135 °C affords the corresponding cyclic ethers such as 20 in excellent yields (Scheme 10.7), while 1,3-diols experience different transformations depending on their structure [112]. The dehydration of 1,2-diols mainly proceeds via the pinacol rearrangement. Further condensation of the initially formed carbonyl compound and unreacted diol affords 1,3-dioxolanes [113]. The catalyst could be efficiently reused following a reactivation protocol. Formation of aryl ethers is also possible, and the synthesis of dibenzofurans 21 (X = O) from 2,2 -dihydroxybiphenyls has been reported (Scheme 10.7) [114]. The related reaction... 

Strecker reaction catalyzed by (i-PrO)4Ti whereby tosylimines accept Me3SiCN enantio-selectively is achieved by modifying the environment surrounding the metal center by alkoxy group exchange with 3,3 -di(P-naphthyl)-2,2 -dihydroxybiphenyl, and further complexation with cinchonine. ... 

Conveniently included in this section, although an aspect of electrophilic substitution, is the synthesis of an unusual 5, 2,2 -biphenyl. By treatment of phenol in nitromethane solution containing 1-oxaspiro[4,5]deca-6,9-diene-2,8-dione briefly during 2 mins, with stannic chloride, followed by refluxing the acidic product with 1% sulphuric acid in methanol for 1 hour, 2,2 -dihydroxybiphenyl-5 -(2-methoxycarbonylethyl)biphenyl has been obtained in 60% yield (ref.35). The reaction also occurred with phenolic ethers and its regiospecificity in the case of phenol may be attributable to hydrogen bonding. 

The next step of PCB-catabolism is catalyzed by a 2,3-dihydrodiol dehydrogenase and regenerates NADH, and leads to the formation of 2,3-dihydroxybiphenyl. With respect to the reaction medianism of the fist two steps of PCB degradation, there is a great similarity to other catabolic pathways of aromatics, like benzene, toluene, benzoate, naphthalene, etc. 

The reaction of pyromellitic dianhydride or benzophenone-3,3, 4,4 -tetra-carboxylic anhydride with amino acids or lactams followed by condensation of the resulting diacids with diacetates of hydoquinone, 2,6-dihydroxynaph-thalene or 4,4 -dihydroxybiphenyl produced layer polymers (42). With the exception of the polymer with y=ll, all the polymers based on Ar = 4,4 -biphenylyl exhibit a smectic mesophase. The polymer with y = 10 and Ar = 1,4-phenylene exhibits a smectic mesophase. Polymers based on Ar = 1,4-phenylene or 2,6-naphthalene melt directly into an isotropic phase. 

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