Ethers aryl, chlorination

The mem-dichlorobenzene complex reacts with protected 0-aryltyrosines to give aryl ethers. Both chlorine atoms can be sequentially substituted to give symmetrical or disymmetrical triaryl diethers (Scheme XVI). The building up of such diaryl ethers from phenolic compounds which have amino groups in their side chains... 

Aryloxymethyl chlorides may be prepared by the reaction of sodium aryloxymethanesulfonates with phosphorus pentachloride. The chlorination of anisole does not, as previously reported, give phenoxymethyl chloride, but rather a mixture of p- and o-chloroanisoles. Similarly, anisole and other unsubstituted methyl aryl ethers undergo ring chlorination with phosphorus pentachloride and chlorine, whereas ring-chlorinated anisoles, such as />-chloroanisole, undergo chlorination at the methyl group with chlorine at 190-195° in the presence of a catalytic amount of phosphorus pentachloride. ... 

Chromium activation allows a strategy for aryl ether synthesis in four stages (i) electrophilic chlorination (ii) chromium coordination (iii) alkoxide substitution for chloride and (iv) oxidative decomplexa-tion.33 The process is effective for the synthesis of 6-methoxytetrahydroquinolines and 5-methoxydihydroindole derivatives, for example. Chlorination of iV-acetyltetrahydroquinoline with SO2CI2 followed by deacetylation provides 6-chlorotetrahydroisoquinoline in 77% yield (equation 11).33 Complexation with [Cr(CO)6] in diglyme-cyclohexane at 125 °C for 53 h using the Strohmeier apparatus gave the chromium complex (13) in 85% yield, based on 40% recovery of starting material. The unre-... 

MC MDI MEKP MF MMA MPEG MPF NBR NDI NR OPET OPP OSA PA PAEK PAI PAN PB PBAN PBI PBN PBS PBT PC PCD PCT PCTFE PE PEC PEG PEI PEK PEN PES PET PF PFA PI PIBI PMDI PMMA PMP PO PP PPA PPC PPO PPS PPSU Methyl cellulose Methylene diphenylene diisocyanate Methyl ethyl ketone peroxide Melamine formaldehyde Methyl methacrylate Polyethylene glycol monomethyl ether Melamine-phenol-formaldehyde Nitrile butyl rubber Naphthalene diisocyanate Natural rubber Oriented polyethylene terephthalate Oriented polypropylene Olefin-modified styrene-acrylonitrile Polyamide Poly(aryl ether-ketone) Poly(amide-imide) Polyacrylonitrile Polybutylene Poly(butadiene-acrylonitrile) Polybenzimidazole Polybutylene naphthalate Poly(butadiene-styrene) Poly(butylene terephthalate) Polycarbonate Polycarbodiimide Poly(cyclohexylene-dimethylene terephthalate) Polychlorotrifluoroethylene Polyethylene Chlorinated polyethylene Poly(ethylene glycol) Poly(ether-imide) Poly(ether-ketone) Polyethylene naphthalate Polyether sulfone Polyethylene terephthalate Phenol-formaldehyde copolymer Perfluoroalkoxy resin Polyimide Poly(isobutylene), Butyl rubber Polymeric methylene diphenylene diisocyanate Poly(methyl methacrylate) Poly(methylpentene) Polyolefins Polypropylene Polyphthalamide Chlorinated polypropylene Poly(phenylene oxide) Poly(phenylene sulfide) Poly(phenylene sulfone)... 

The kinetics of the chlorination of phenol and 2-naphthol by l,3-dichloro-5,5-dimethylhydantoin (2) in aqueous acidic media have been interpreted10 in terms of an initial rate-limiting formation of a charge-transfer complex between the substrate and the chlorinating agent. A kinetic study of the chlorination of nine aryl ethers by 1-chlorobenzotriazole in acetic acid has also led to mechanistic conclusions.11... 

There is one very special feature of the benzyne mechanism. The triple bond could be attacked by nucleophiles at either end. This is of no consequence when we are dealing with bromo benzene as the products would be the same, but we can make the ends of the triple bond different and then we see something interesting, ortho-Chloro aryl ethers are easy to prepare by chlorination of the ether (Chapter 22). When these compounds are treated with NaNH2 in liquid ammonia, a single amine is formed in good yield. 

O-Demethylation has been observed as well as, or instead of, nucleophilic displacement on reaction of 3,4,5-chloro/methoxy pyridazines and 4,5-chloro/methoxy-2-methyl-3(2//)-py-ridazinones with morpholine (e.g.. Scheme 63). Demethylation was observed at all ring positions, but usually adjacent to chlorine or a carbonyl group, and A -methylmorpholine was isolated, consistent with demethylation rather than hydrolysis. The demethylation can also occur with other primary and secondary amines such as diethylamine, butylamine, and piperidine, but not with pyrrolidine and aniline <87H(26)1 >. 3-Phenolic ethers of pyridazines are resistant to reductive cleavage of the aryl ether bond under the conditions of phase transfer catalytic hydrogenolysis <82T3775>. 

Aryl ethers can be chlorinated in the ring by Cl2, by a glacial acetic acid solution of S02C12 (the amount of which is easily measured), or by PC15. 

The synthesis of 86 commenced with oxazole carboxylic acid 87. Base-catalyzed lithiation and coupling with isatin 88 followed by methyl ester formation and Boc deprotection provided tertiary alcohol 89. A second coupling of the amine 89 with carboxylic acid 90 followed by chlorination afforded chloride 91. Treatment of 91 with TBAF gave a 1 1 mixture of O-aryl ether 92 (CIO) in excellent yield. Refluxing 92 in chloroform resulted in the formation of 93 (70%, with 30% of the isomer), which was subjected to a three-step reaction sequence to furnish intermediate 86 (Scheme 16). 

Louw and Franken [18] could convert anisole into trichloromethyl anisole by photochlorination with elemental chlorine in refluxing tetrachloromethane. Feiring [19] could show more recently, that the trichloromethyl aryl ethers can be in situ converted into the final trifluoromethyl aryl ethers by treatment with HF. 

Yarovenko and VasiTeva [20] developed an approach based on aryl chlorothio-noformates. They can be cleanly converted by chlorination into trichloromethyl aryl ethers. This step is then followed by fluorination using antimony trifluoride and a catalytic amount of antimony pentachloride. 

The synthesis and characterization of a full aromatic thermotropic liquid crystalline poly (aryl ether ketone) with pendant chlorine group (CIPAEK)... 

Depending on the ring substituent, trifluoromethoxyben2enes can be made by the sequential chlorination—fluorination of anisole(s) (351—354). A one-step process with commercial potential is the BF (or SbF2)-cataly2ed reaction of phenol with carbon tetrachloride/hydrogen fluoride (355). Aryl trifluoromethyl ethers, which may not be accessible by the above routes,may be made by fluorination of aryl fluoroformates or aryl chlorothioformates with sulfur tetrafluoride (348) or molybdenum hexafluoride (356). 

The reaction is carried out by first reacting the alkyl or aryl halide with magnesium shavings in an ether suspension and then treating with silicon tetrachloride (prepared by passing chlorine over heated silicon). With methyl chloride the following sequence of reactions occur ... 

Phenoxyalkanoates. There has been considerable interest in the persistence of chlorinated phenoxyalkanoates—and particularly of phenoxyacetates and phenoxypropionates, which have been used as herbicides. This has therefore stimulated studies on the degradation of these aryl-alkyl ethers. Considerable effort has been directed to elucidating the subsequent... 

The reaction can be carried out efficiently using aryl diazonium tetrafluoroborates with crown ethers, polyethers, or phase transfer catalysts.103 In solvents that can act as halogen atom donors, the radicals react to give aryl halides. Bromotrichloromethane gives aryl bromides, whereas methyl iodide and diiodomethane give iodides.104 The diazonium ions can also be generated by in situ methods. Under these conditions bromoform and bromotrichloromethane have been used as bromine donors and carbon tetrachloride is the best chlorine donor.105 This method was used successfully for a challenging chlorodeamination in the vancomycin system. 

Halogenatlon. Poly(2,6-dimethyl- and 2,6-diphenyl-l,4-phenylene ether) can be aryl-brominated simply by exposure to a bromine solution no catalyst is required.6 In fact, the use of Lewis acid catalysts to promote the chlorination of poly(2,6-dimethy1-1,4-phenylene ether) leads to substantial degradation of the molecular weight of the chlorinated products.7 Membranes produced from ring brominated PPO (40% wt Br) exhibited enhanced permeability to CHi and CO2 and proved to be more selective in separating CH4/CO2 mixtures.8... 

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