Anisole arylation

Friendly Route to Anisoles, Aryl Propionic Acids, and N-Methyl Anilines, Book of Abstracts, 218th ACS National Meeting, American Chemical Society, Washington, D.C., 1999. 

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). 

Sulfation by sulfamic acid has been used ia the preparation of detergents from dodecyl, oleyl, and other higher alcohols. It is also used ia sulfating phenols and phenol—ethylene oxide condensation products. Secondary alcohols react ia the presence of an amide catalyst, eg, acetamide or urea (24). Pyridine has also been used. Tertiary alcohols do not react. Reactions with phenols yield phenyl ammonium sulfates. These reactions iaclude those of naphthols, cresol, anisole, anethole, pyrocatechol, and hydroquinone. Ammonium aryl sulfates are formed as iatermediates and sulfonates are formed by subsequent rearrangement (25,26). 

ArH = dimethoxybenzenes, anisol, xylenes, fluorene, diphenyl ether, etc R = alkyl, aryl... 

Arenediazonium ions are relatively weak electrophiles, and therefore react only with electron-rich aromatic substrates like aryl amines and phenols. Aromatic compounds like anisole, mesitylene, acylated anilines or phenolic esters are ordinarily not reactive enough to be suitable substrates however they may be coupled... 

Methyl aryl ethers, such as anisole, are cleaved to iodomethane and a phen-oxide ion by treatment with Li) in hot DMR Propose a mechanism for this reaction. 

Aromatic compounds that do not contain meta-directing groups can be converted to diarylamines by treatment with aryl azides in the presence of phenol at — 60°C ArH -f- Ar N3 —> ArNHAr. Diarylamines are also obtained by the reaction of N-arylhydroxylamines with aromatic compounds (benzene, toluene, anisole) in the presence of F3CCOOH ArH -f Ar NHOH ArNHAr. ... 

However, the Buchwald-Hartwig reaction with NHCs as hgands is not limited to palladium. Nickel has also been successfully employed in this catalytic amination. In situ procedures have been described for the coupling of aryl chlorides [163] and tosylates [164] and, more interestingly, anisoles [165]. The use of well-defined Ni(0) catalysts has also been studied [166] (Scheme 6.49). 

A, and fl = 90.48°. The 2-pyridyl ring and p-tolyl group make dihedral angles of 29.7° and 55.3° respectively with the double bond plane. The inter-aryl dihedral angle is 106.5°. The data was obtained on crystals grown from a solution of the compound in anisole. A Picker FACS-1 diffractometer with CuK radiation was used for the measurements, or... 

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. ... 

Some aryl iodides are known to generate the diaryImercury at a mercury cathode. In the case of 4-iodoaniso e, reduction at more negative potentials in dimeth-ylfonnamide leads to the formation of less di(4-methoxyphenyl)mercury. At glassy carbon, anisole is the only reduction product. 4-Bromoanisole gives only anisole at either mercury or carbon [143]. Mercur> has been used as cathode material for many preparative experiments with aryl halides but glassy carbon and also stainless steel are very satisfactory alternatives. 

Generating T electrochemically, then examining its 5-arylation with anisole, 2,6-dimethylanisole, cumene, and 1,4-dimethoxybenzene, showed that the exact mechanism depends on the oxidation potential of the particular aromatic component When high, relative to thianthrene, a sequence summarized by Eqs. (28)-(30)... 

Klumpp and Sinnige proceeded similarly, using ec-butyl alcohol to protodelithi-ate the anisoles and other lithiated aryl ethers in di-n-butyl ether. The protodelithiation enthalpies for all the lithiated aryl ethers, as monomers, from the latter study are listed in Table 3. The reaction enthalpies for the o- and p-lithioanisoles are ca 20 kJmop more negative from Reference compared to the ones from Reference, presumably due to differences in the reaction media. From the exchange reaction, equation 17, and the enthalpies of formation of phenyl lithium, benzene and the relevant aryl ether, the enthalpies of formation of the lithiated aryl ethers can be derived. The calculated values are shown in Table 3. 

The organolithium compounds, formed by deprotonation of Af-benzylic-Af-Boc p-anisole carbamates, react with imines to yield tran5-4,5-disubstituted 1,3-imidazolin-2-ones in good yield and excellent stereoselectivity (Scheme 52). Benzaldehydes gave poor stereoselectivity, and the nse of imines as electrophiles is critical. The stereoselectivity can be explained by the transition states shown, in which the aryl and R substituents on the 4-membered ring are trans to one another. 

Scheme 12.12 Formation of the arylated heterofullerene 34 from bis-azafulleroid and ketolactam precursors, (i) n-Butylamine, ODCB-anisole, p-TsOH, air, reflux (ii) ODCB-anisole, p-TsOH, air, reflux.

Cycloadditions have been carried out to 37/-indoles (222, 223) (125,126), N-arylmaleimides (224) (127,128), l,2), -azaphospholes (225) (129), 5(47/)-oxazo-lones (226) (130), and 4,5-dihydrooxazoles (230) (131). The primary cycloadducts from the reaction of oxazolones (e.g., 226 with diaryl nitrile imines), derived from tetrazoles in refluxing anisole, do not survive. They appear to lose carbon dioxide and undergo a dimerization-fragmentation sequence to give the triazole 228 and the diarylethene 229 as the isolated products (130). In cases where the two aryl substituents on the oxazole are not the same, then, due to tautomerism, isomeric mixtures of products are obtained. 

There is direct evidence, from ir and nmr spectra, that the f-butyl cation is quantitatively formed when f-butyl chloride reacts with A1CI3 in anhydrous liquid HCI.246 In the case of olefins, Markovnikov s rule (p. 750) is followed. Carbocation formation is particularly easy from some reagents, because of the stability of the cations. Triphenylmethyl chloride247 and 1-chloroadamantane248 alkylate activated aromatic rings (e.g., phenols, amines) with no catalyst or solvent. Ions as stable as this are less reactive than other carbocations and often attack only active substrates. The tropylium ion, for example, alkylates anisole but not benzene.249 It was noted on p. 337 that relatively stable vinylic cations can be generated from certain vinylic compounds. These have been used to introduce vinylic groups into aryl substrates.250... 

Most of the side reactions have already been discussed in Section 26.1.3.3. (dediazoniation in organic solvents). Chlorinated aliphatic solvents, such as 1,2-dichloroethane and dichloro-methane, lead to an extensive formation of chloroaromatics, and aromatic solvents, even halogenated examples, can be arylated to some extent by arenediazonium tetrafluoroborates (vide supra). For example, during dediazoniation of benzenediazonium tetrafluoroborate in toluene, chlorobenzene, bromobenzene or anisole, 3-5 % of substituted biphenyls Ph-C6H4-X (X = Me, Cl, Br, OMe) are formed together with 0.5-0.8% of fluorobiphenyls.5 Fluorobiphenyls are formed through an ionic pathway (only 2- and 4-isomers are formed) whereas chlorobiphenyls result from a radical process (X = Cl, 2-/3-/4-isomer 26 47 27).243... 

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