Reactions of aryl ethers

Nitromifene (85) is such an agent. A Grignard reaction of aryl ether and ketone leads to tertiary carbinol Tosic acid dehydration leads to a mixture of 1 and stilbenes which constitute the antiestrogen, nitromi fene (85)... 

Pyridinium chloride ([PyHjCl) has also been used in a number ofcyclization reactions of aryl ethers (Scheme 5.1-4) [4, 18]. Presumably the reaction initially proceeds by deallcylation of the methyl ether groups to produce the corresponding phenol. The mechanism of the cyclization is not well understood, but Pagni and Smith have suggested that it proceeds by nucleophilic attack of an Ar-OH or Ar-0 group on the second aromatic ring (in a protonated form) [4]. 

Carboxonium-carbenium dications have also been proposed in the reactions of aryl ethers, phenols, and naphthols, with superacids. When 2-naphthol is reacted with an excess of AICI3 (3 equivalents) and cyclohexane, the product of ionic hydrogenation is observed in 59% yield (eq 15).24 This conversion is thought to occur by double protonation of the 2-naphthol ring to give the dication 48, which is capable of abstracting hydride from cyclohexane. Similar intermediates are formed by the reactions of HF-SbFs with naphthyl ethers (eq 16).25... 

Pyridinium chloride ([PyH]Cl) has also been used in a number of cyclization reactions of aryl ethers [82,85] (Scheme 5.2-53). Presumably the reaction initially... 

In 2004 Kakiuchi disclosed that atkoxyarenes bearing an ortho carbonyl group can be coupled with arylboronic esters in the presence of RuH2(CO)(PPh3)3 [Eq. (16)] [65]. The reaction represents the first example of a Suzuki-Miyaura-type reaction of aryl ethers. Chelation assistance facilitates the oxidative addition of C-O bonds, which allows for a regioselective C-O bond cleavage of diaryl ethers. 

Hexfluorophosphate salts behave similarly.108 The diazonium tetrafluoroborates can be prepared either by precipitation from an aqueous solution by fluoroboric acid109 or by anhydrous diazotization in ether, THF, or acetonitrile using r-butyl nitrite and boron trifluoride.110 Somewhat milder reaction conditions can be achieved by reaction of aryl diazo sulfide adducts with pyridine-HF in the presence of AgF or AgNQ3. 

Reactions of aryl halides with phenoxides or phenols (Equation (30)) and base catalyzed by complexes of these ligands occurred in significantly higher yields than did the same reactions catalyzed by complexes of DPPF or BINAP. For example, a large number of diaryl ethers have... 

More recently, reductive elimination of aryl ethers has been reported from complexes that lack the activating substituent on the palladium-bound aryl group (Equation (55)). These complexes contain sterically hindered phosphine ligands, and these results demonstrate how steric effects of the dative ligand can overcome the electronic constraints of the reaction.112,113 Reductive elimination of oxygen heterocycles upon oxidation of nickel oxametallacycles has also been reported, but yields of the organic product were lower than they were for oxidatively induced reductive eliminations of alkylamines from nickel(II) mentioned above 215-217... 

The Ullman reaction, discovered in 1903,2 is the prototype cross-coupling method for the synthesis of aryl ether... 

After the initial demonstration of stoichiometric nucleophilic attack on 7i-allyl ligands, catalytic allylic substitution reactions were pursued. In 1970, groups from Union Carbide [3, 4], Shell Oil [5], and Toray Industries [6] published or patented examples of catalytic allylic substitution. All three groups reported allylic amination with palladium catalysts. The Toray Industries report also demonstrated the exchange of aryl ether and ester leaving groups, and the patent from Shell Oil includes catalysts based on rhodium and platinum. 

Table 2 contains the characteristics of the amic ester-aryl ether copolymers including coblock type, composition, and intrinsic viscosity. Three series of copolymers were prepared in which the aryl ether phenylquinoxaline [44], aryl ether benzoxazole [47], or aryl ether ether ketone oligomers [57-59] were co-re-acted with various compositions of ODA and PMDA diethyl ester diacyl chloride samples (2a-k). The aryl ether compositions varied from approximately 20 to 50 wt% (denoted 2a-d) so as to vary the structure of the microphase-separated morphology of the copolymer. The composition of aryl ether coblock in the copolymers, as determined by NMR, was similar to that calculated from the charge of the aryl ether coblock (Table 2). The viscosity measurements, also shown in Table 2, were high and comparable to that of a high molecular weight poly(amic ethyl ester) homopolymer. In some cases, a chloroform solvent rinse was required to remove aryl ether homopolymer contamination. It should also be pointed out that both the powder and solution forms of the poly(amic ethyl ester) copolymers are stable and do not undergo transamidization reactions or viscosity loss with time, unlike their poly(amic acid) analogs.

Similarly, C—Se bonds are formed by an internal homolytic substitution of aryl radicals at selenium, with the preparation of selenophenes and benze-neselenophenes [75]. Scheme 7.7 illustrates the reaction of aryl iodides 61 with (TMS)3SiH, which afforded benzeneselenophenes in good yields. The presence of (TMS)3SiI after the reduction induced the final dehydration of the intermediate 3-hydroxyselenophenes, presumably through an intermediate silyl ether. 

Kamal A, Prasad BR, Khan MNA (2007) TMSCl-Nal-mediated reaction of aryl azides with cyclic enol ethers an efficient one-pot synthesis of 1,2,3,4-tetrahydroquinolines. J Mol Catal A Che 274 133-136... 

A polymer-bound guanidine base 31 has been used for the formation of aryl ethers from suitable phenols and alkyl halides. In addition to serving as a base to affect deprotonation, reagent 31 also acts as a sequestering agent for excess starting phenol (reaction 11).26... 

Reactions of aryl or alkyl bis(siloxy)isopropyl ethers with tetrabutyl-ammonium fluoride-mesyl fluoride reagent lead to replacement of one siloxy group by fluorine and dehydrosiloxylation, providing an efficient access to fluoroisopropenyl ethers, which are useful as specific building blocks in drug design The reactions proceed via the intermediate allyl methanesulfonates [30, 31] (equation 23)... 

The distinction between electrophilic and electron-transfer mechanisms of addition reactions to vinyl double bonds of ArX—CH=CH2 (X = S, O, Se) has been achieved by studying substituent effects. Specifically, the effects of meta and para substituents on the rates of electrophilic additions correlated with Hammett radical cations correlates with statistical tests. The ofclcctrophilicj/o-1 (FT) dichotomy is in accord with the conventional paradigm for cr/cr+ correlations and further support has been found by ah initio calculations. Interestingly, the application of this criterion to the reactions of aryl vinyl sulfides and ethers with tetracyanoethylene indicates that cyclobutanes are formed via direct electrophilic addition to the electron-rich alkene rather than via an electron-transfer mechanism.12... 

It has been found that the use, as ligands, of electron-poor phosphines, such as 1,1 -bis(diphenylphosphino)ferrocene, enhances yields in the palladium-catalysed reaction of aryl bromides with sodium phenoxides to yield diaryl ethers.87 Palladium-catalysed coupling of ethynylated derivatives of bipyridine or terpyridine with the corresponding bipyridine or terpyridine halides or triflates has been used in the synthesis of preorganized polytopic ligands.88... 

I he reaction of aryl trimethylsilyl ethers catalyzed by (CH3),SiOTf with the D-ttlucosidc la (nnomeric mixture) results in the formation of essentially only the aryl -/ -Itlueosidc. ... 

The Pd-catalysed intermolecular reaction of aryl bromides containing electron-withdrawing substituents with a wide variety of alcohols including MeOH, 2-propanol, benzyl alcohol and i-butyl alcohol gives the aryl ethers 416 under milder conditions than uncatalysed reactions. Bidentate ligands such as BINAP and DPPF (XLIX) are effective [206,207]. The aryl Pd alkoxide 417 was isolated as an intermediate, and the formation of the aryl ethers 418 by reductive elimination of 417 was confirmed. 

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