Diarylethers

With alcohols or more often with alcoholates (refs. 51 - 56) or phenolates (refs. 57 - 64) the arylethers are formed. Typically, one of the Ullmann reactions is corresponding to the diarylethers synthesis. 

Halden RU, Peters EG, Halden BG, Dwyer DF (2000) Transformation of mono- and dichlorinated phenoxybenzoate-dioxygenase in Pseudomonas pseudoalcaligenes POB310 and a modified diarylether-metabolizing bacterium. Biotechnol Bioeng 69 107-112... 

Most photo-oxidations that occur via the Frei hybrid type II vOi - type II/ivRH mechanism have been conducted in the absence of solvent, which can shield the substrate from the infrazeolite electrostatic field. The exceptions include the photo-oxidations of easily ionized substrate [50,51] that will react even in solvent slurries [10]. For example, Ramamurthy and co-workers [52] reported that irradiation into the oxygen-CT bands (>350 nm) for a series of 1,1-diaryleth-ylenes, 23, in hexane slurries resulted in the formation of oxidized products via the Frei mechanism (Fig. 19). 

JMC5020>. Imidazole-containing diarylether and diarylsulfone inhibitors of famesyl-protein transferase has been described <99BML3301>. 

Electrochemical methods have also been exploited to advantage for effecting the critical para-ortho coupling of certain diarylethers as exemplified by the anodic oxidation of 320 to provide 321 (164). Although the conversion of 321 to galanthamine (291) remains to be reported, it is already evident that this entry to this family of alkaloids has considerable potential and merits further investigation. 

A partial dearylation of diarylether during nitration had already been observed by Reilly, Drumm and Barrett [154], The dealkylation, observed by Schramm and Westheimer, has been confirmed by Ingold and his co-workers [152], For example p- chloroanisole, when nitrated with a 6N solution of nitric acid in the presence of acetic acid at 20°C gave 4-chloro-2-anisole in 66% yield and 4-chloro-2,6-dinitrophenol in 33% yield of theory. 

Several different approaches to the construction of poly(arylene-carborane)s were initially considered (Scheme 1). These included (i) nucleophilic polycondensation between a bis-phenol and an activated, carborane-based dihalide in the presence of base, a reaction used for the synthesis of commercial polyetherketones and polyethersulfones,4 (ii) electrophilic polycondensation between an aromatic diacid and a carborane-based diarylether in the presence of a strong-acid catalyst,5 and (iii) direct, homogeneously-catalysed coupling of a carborane-based dihalide.6 However,... 

Diarylheptanoids constitute a distinct group of natural plant metabolites characterized by two aromatic rings linked by a linear seven-carbon aliphatic chain. They may be divided into two subgroups, i.e. open chain and macrocyclic diarylheptanoids. In the latter the aromatic rings are connected to form a diarylether or a biaryl moiety. 

Macrocyclic diarylheptanoids can be derived from linear ones by oxidative cyclization. This is supported by the fact that in all of the biaryl type representatives the aryl-aryl bond is in meta position relative to both ends of the seven-carbon chain, while in those containing a diarylether bond a meta,para bridging can be identified. This substitution pattern corresponds to activation of the position ortho to the phenolic hydroxy group. Biosynthesis of cyclic diarylheptanoids was investigated by Inoue et al. (84). They fed [1- C] and... 

First the diarylether 158 was prepared by reacting isovanilline with methyl 4-bromobenzoate. 158 was condensed with the phosphonium salt 159 obtained in three steps from the readily available methyl 5-methylisoxazol 3-carboxylate. 

Mauler F, Mittendorf J, Horvath E, De Vry J (2002) Characterization of the diarylether sul-fonylester(-)-(R)-3-(2-hydroxymethylindanyl-4-oxy)phenyl-4,4,4-trifluoro-l-sulfonate (BAY 38-7271) as a potent cannabinoid receptor agonist with neuroprotective properties. J Pharmacol Exp Ther 302 359-368... 

Recently, a novel class of diarylether sulfonyl ester cannabinoid agonists possessing neuroprotective properties was reported by Bayer AG (Wuppertal, Germany) (Mauler etal. 2002). The representative agonist, (-)-R-3-(2-hydroxy-methyl-indanyl-4-oxy)phenyl-4,4,4-trifluoro-l-sulfonate (65, BAY38-7271, Fig. 18), is a high-affinity CBi ligand (K, = 0.46-1.85 nM rat brain, human cortex, and recombinant human CBi receptor) (Mauler et al. 2003). 

A range of unsymmetrical polychlorinated diarylethers have been obtained by this reaction in modest to good yields. 

Intramolecular decomposition of (aryloxy)tetraphenylantimony (9) by thermolysis leads to the corresponding diarylethers (15) in modest to Wgh yields. 

Almost every type of flavonoids form dimers via C-C or diarylether linkages, but dimeric flavones are more common than dimeric isoflavones. In batramiaflavone two biaryl bonds can be found. Homodimers such as biscyclolobin and heterodimers such abiesin both exist. In the latter even the oxidation level of the monomers may differ. Important members of this group are the... 

As shown in Section 2 diarylethers are also widely occurring structural units in natural products. Despite its serious drawbacks, up to relatively recently, Ullmann s procedure was almost exclusively the method of choice for preparing diarylethers. According to the original methodology, phenols and aryl halides can be coupled to diarylethers in the presence of activated copper powder and potassium carbonate [134] (Scheme 54). 

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