Alkyl aryl ethers phenols

In 2004-2005, we reported direct etherification of tautomerizable heterocycles with oxygen nucleophiles via phosphonium coupling to produce biaryl ethers or alkyl aryl ethers. Phenols are moderately strong nucleophiles, therefore the NaOi-Bu-promoted phosphonium coupling condition was found to be better than the Et3N-promoted condition (04AP702,05JOC1957). 

Cleavage of alkyl aryl ethers by hydrogen halides always proceeds so that the alkyl-oxygen bond is broken and yields an alkyl halide and a phenol as the final prod nets Either hydrogen bromide or hydrogen iodide is normally used... 

Section 24 12 The cleavage of alkyl aryl ethers by hydrogen halides yields a phenol and an alkyl halide... 

Alkyl aryl ether Hydrogen halide A phenol Alkyl halide... 

Alkyl aryl ethers (CXVII) undergo rearrangement in the presence of Lewis acid and strong acid catalysts to give the corresponding alkyl phenols (CXVIII and CXIX), viz. 

Dialkyl and alkyl aryl ethers can be cleaved with iodotrimethylsilane ROR -bMe3SiI — Rl-bMe3SiOR. A more convenient and less exjjensive alternative, which gives the same products, is a mixture of chlorotrimethylsilane and Nal. Alkyl aryl ethers can also be cleaved with Lil to give alkyl iodides and salts of phenols in a reaction similar to 10-73. Triphenyldibromophosphorane (Ph3PBr2) cleaves dialkyl ethers to give 2mol of alkyl bromide. ... 

A A liquid soluble in pentane 65 Mostly aliphatic material with some mono-aromatic parts broken off the coal by C-C cleavage. Apart from combined-phenol it has negligible polar material It contains some free paraffinic material, but exists mostly as alkyl phenols and alkyl-aryl ethers... 

The Effect of Phenol. Three types of phenol compounds have been identified in the fractions derived from the product of the phenol ati on reaction (.1,2) alkyl phenols and alkyl-aryl ethers, both formed by combining phenol with alkyl side chains cleaved from the coal molecule, and compounds made up of aromatic fragments attached to phenol by a methylene bridge, formed by... 

Table 7.11. Preparation of alkyl aryl ethers from support-bound phenols.

Alternatively, alkyl aryl ethers can be prepared from support-bound aliphatic alcohols by Mitsunobu etherification with phenols (Table 7.13). In this variant of the Mit-sunobu reaction, the presence of residual methanol or ethanol is less critical than in the etherification of support-bound phenols, because no dialkyl ethers can be generated by the Mitsunobu reaction. For this reason, good results will also be obtained if the reaction mixture is allowed to warm upon mixing DEAD and the phosphine. Both triphenyl- and tributylphosphine can be used as the phosphine component. Tributyl-phosphine is a liquid and generally does not give rise to insoluble precipitates. This reagent must, however, be handled with care because it readily ignites in air when absorbed on paper. 

Nafion-H is also very efficiently catalyzes the rearrangement of anisole, methy-lanisoles, and phenetole to ring-alkylated phenols and products of transalkylation when vapors of the alkyl aryl ethers are passed over it at temperatures higher than 160°C. At these reaction temperatures, some of the starting alkyl phenyl ethers... 

The condensation of tellurium tetrachloride with aromatic compounds was one of the first methods for the preparation of aryl tellurium trichlorides. Alkyl aryl ethers react easily with tellurium tetrachloride in refluxing chloroform or carbon tetrachloride (Vol. IX, p. 1153). The trichlorotelluro group enters in the /wa-position to the alkoxy group. Several additional monosubstituted benzenes and substituted phenols were found to condense with tellurium tetrachloride (Table 7, p. 306). 

Aryl ethers. Phenols are converted into methyl ethers by reaction with 1 in the presence of potassium carbonate and 18-crown-6 at 150°. The reaction involves liberation of chloroform and carbon dioxide (equation 1). If the reaction is conducted in the presence of an alkyl halide, alkyl aryl ethers are formed in generally good yield (equation 11). 

Alkyl aryl ethers. This fluoride can serve as base for the alkylation of phenols with alkyl halides (DMF, 20°). Yields are in the range 65-85%. In the case of 2,6-disubstituted phenols the reaction is conducted at 100°. The method is even satisfactory for alkylation of 2- and 4-nitrophenols. The success of this method probably is a result of the ability of to serve as a hydrogen-bond electron donor. 

Cleavage of ethers, Dialkyl and alkyl aryl ethers are cleaved by 47% hydro-bromic acid in an aqueous organic solvent in the presence of an onium salt (hexadecyltributylphosphonium bromide, tetraoctylammonium bromide) that is completely soluble in the organic phase. Dialkyl ethers are converted into alkyl bromides (65-90% yield),whereas a phenol and an alkyl bromide are obtained from alkyl aryl ethers (85-90% yields). 

The cleavage of alkyl aryl ethers is more important as a preparative method for phenols than for alkyl halides (method 97). The procedure has been employed as the final step in a synthesis proposed as a means for increasing the carbon chain of an alkyl halide, viz., ... 

Aluminum and boron halides are sometimes used to dealkylate alkyl aryl ethers to phenols. Boron tribromide cleaves aliphatic ethers to alcohols and alkyl halides, but the reaction has no preparative value in the aliphatic series. Aluminum halide and the ether first form a complex from which a molecule of alkyl halide is eliminated upon heating. 

Alkyl aryl ethers are qnite stable on heating. Phenyl benzyl ether isomerizes slowly at 250 °C to afford 4-benzylphenol and its ortho-i ovasc as a minor prodnct" . The conditions of isomerizations of O-aUcylated and O-aralkylated phenols were reviewed . 

In the HP-SbP, system the O-alkyl group of alkyl aryl ethers bearing p-alkyl or 2,6-dialkyl substituents rearranges to the meta position of the aromatic nucleus (Scheme 14,18) [45], Diprotonation of para-substituted phenols with I IP-Sbly occurs at the oxygen and meta carbon atoms, and the resulting diprotonated species undergo Friedel-Crafts alkylation with arenes [46],... 

Preparation of alkyl aryl ethers by loss of water between a phenol and an alcohol is generally of little importance. It may, however, be noted that phloro-glucinol can be converted into di- or tri-alkyl ethers by means of hydrochloric acid 679 also some naphthols, anthracenols, and phenanthrols,680 e.g., oc- and... 

Alkyl aryl ethers can also be obtained by Claisen s method 701 the phenol is treated with an alkyl bromide in boiling acetone (water-bath) containing potassium carbonate. The alkyl chloride in admixture with potassium iodide may be used instead of the alkyl bromide.753, 754 The acetone may be replaced... 

When an excess of hydrogen iodide is used with aliphatic ethers, both portions of the molecule are to be expected as alkyl iodides, but alkyl aryl ethers always give alkyl iodide and the phenol ... 

When an excess of the acid is applied, symmetrical alkyl ethers give the corresponding alkyl sulfonate as sole product, since the alcohol formed as intermediate is rapidly esterified this reaction is thus to be recommended for the preparation of alkyl sulfonates, though it should be noted that the water formed slows down the process the aryl-oxygen bond of alkyl aryl ethers is not broken, these compounds giving the alkyl sulfonate and the corresponding phenol. 

Alkyl aryl ethers. Two laboratories have reported independently that alkyl aryl ethers can be prepared by reaction of an alcohol and a phenol with this combination of reagents. The reaction proceeds with inversion in the case of 3j3-cholestanol (but not cholesterol). The reaction proceeds at room temperature inTHF. 

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