Allylphenyl ether

RhCKCOD) ] + AgBF + 125 1-heptene, 1-octene, styrene, allylbenzene allylphenyl ether [49]... 

Ru(H20)6], which is a precursor of ROM polymerization of cyclic dienes has also been found to possess good alkene isomerization activity [1], Among others it catalyzed the isomerization of allylphenyl ether to a vinylphenyl ether (Scheme 9.1) at room temperature. Allyl ethers are stable to acids and bases, while vinyl ethers are easily cleaved in acidic solutions. Therefore this isomerization gives a mild method for removal of protecting allyl groups under exceedingly mild conditions. 

The extent of C-alkylation as a side reaction in etherification varies about 1% of allyl 2-allylphenyl ether is formed when phenol is used in the acetone and potassium carbonate method with allyl bromide with cinnamyl bromide or 7,7-dimethylallyl bromide the extent of C-alkylar tion is greater.16 A complicated mixture of C- and O-alkylation products results from the treatment of phenol with 4-bromo-2-hexene and 4-chloro-2-hexene. 9 4-Hexenylresordnol has been obtained in about 40% yield from the reaction of l-bromo-2-hexene, resorcinol, and potassium carbonate in boiling acetone.99 An appreciable amount of C-alkylation occurs when 2,6-dimethyIphenol is treated with allyl bromide and sodium ethoxide in ethanol.70 Since, in general, the ampunt of C-alkylation is greatly increased by carrying out the alkylation on the sodium salt of the phenol in benzene,16 this method is unsuitable for the preparar tion of allyl aryl ethers. 

Preparation of Allyl Phenyl Ether, f A mixture of 188 g. of phenol, 242 g. of allyl bromide, 280 g. of finely ground calcined potassium carbonate, and 300 g. of acetone is refluxed on the steam bath for eight hours. A heavy predpitate of potassium bromide begins to form soon after the refluxing is started. After cooling, water is added the product is taken up in ether and washed twice with 10% aqueous sodium hydroxide solution. The ether solution is dried over potassium carbonate, and, after removal of the ether, the residue is distilled under diminished pressure. The yield is 230 g. (86%), b.p. 85°/19 mm., dll 0.9845. The residue is so small (6 g.) that the distillation might be omitted unless a very pure product is desired. About 1% of allyl 2-allylphenyl ether (a product of C-alkylation) is formed by this procedure. 

Another example describes the Claisen rearrangement of allylphenyl ethers in ionic liquids mainly based on the l,8-diazabicyclo[5.4.0]-7-undecenium cation. Under the chosen conditions, with scandium(III) triflate as catalyst, these substrates were found the undergo a subsequent cyclisation reaction.[134]... 

The residue is so small (6 g.) that the distillation might be omitted unless a very pure product is desired. About 1% of allyl 2-allylphenyl ether (a product of C-alkylation) is formed by this procedure. 

The last consideration is the reactivity of the Grignard reagent with the solvent itself. Deleterious reactions of the Grignard reagent with ethereal solvents occurs only under extreme conditions and has been observed, to some extent, in diethyl ether, di-n-butyl ether, THF, r-butylmethyl ether, anisole (155°C), DME, and allylphenyl ether [Eq. (7) 19-24], Since these reactions occur only under extreme conditions, the ethereal solvents are preferred because of the high Grignard reagent solubility (up to 4 M). 

In the same way, Brdnsted acid catalysts such as trifluoroacetic acid substantially accelerate the Claisen rearrangement of allylphenyl ether. However, the initially formed allylphenols generally react further under the acidic reaction conditions. For instance, crotyl p-tolyl ether (219) in trifluoroacetic acid affords benzofuran 220 as the main reaction product derived from cyclization of the Claisen rearrangement product 221 (equation 151) . ... 

For further examples of regioselective rearrangements with organoaluminum reagents see refs 123 and 129. For organoaluminum-promoted rearrangements of allylphenyl ethers see ref 140. 

The isomerization of allylphenyl ether to o-allylphenol, the Claisen rearrangement, forms an important historical touchstone for 3,3-sigmatropic shifts and... 

The easily available allylphenyl ethers are ozonized at -40°C, treated with DMS giving solutions of the corresponding phenoxyacetalde-hydes, which are purified by column chromatography. Their reaction with 1-methyl-1-phenylhydrazine yields the corresponding hydrazones [73]. 

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