Benzyl phenyl ethers, rearrangement

Alkyl and benzyl aryl ethers undergo acid-catalysed rearrangement to afford phenols. For instance, benzyl phenyl ether under treatment with AlBrs in dichloromethane yields exclusively 2-benzylphenol with simultaneous production of phenol. The ratio of phenol and 2-benzylphenol is hardly affected by the solvent. Other type of catalysts have also been used successfully in this type of rearrangement. For instance, trifluoroacetic acid converts 4-(2 -methyl-but-2 -yl)phenyl benzyl ether (205) to the corresponding phenol 206 (equation 136) and over montmorillonite clays, benzyl phenyl ether (207), is converted to 2-benzylphenol (208) (equation 137) . 

The rearrangement reaction of a variety of alkyl phenyl ethers over a dealumi-nated HY zeolite has been shown to involve both intramolecular and intermolecular processes to afford phenol, (alkoxyalkyl)benzenes and alkylphenols as the main products. o-Benzylphenol has been obtained as the exclusive product in the rearrangement of benzyl phenyl ether in the presence of montmorillonite. The mechanism for a novel zeolite /3-catalysed rearrangement of alkoxybenzyl allyl ethers to aldehydes and ketones has been investigated by the use of cross-over reactions and deuterium labelling. The reaction was found to be mainly intramolecular and has been described as a nucleophilic attack of the double bond on the electrophilic benzylic carbon of the ether-Lewis acid complex, followed by a... 

A similar unsuccessful attempt to perform a Claisen rearrangement on benzyl vinyl ether 7 resulted in a highly successful 1,3-benzyl shift to afford ethyl 3.3-dilluoro-2-oxo-4-phenyl-butanoate (8) in 82% yield.10... 

While allyl and glycidyl ethers are converted into a mixture of oxetane and oxepine products with xec-butyllithium, Mordini and co-workers reported that allyl, benzyl, and propargyl epoxy ethers can be regioselectively converted into 2-vinyl, 2-phenyl, or 2-aIkynyl-3-(hydroxyalkyl) oxetanes upon treatment with either Schlosser s base or other mixed metal bases. Some of the best results were obtained with the LDA/potassium ferf-butoxide mixture (LIDAKOR, ref 194). While rearrangement of propargylic or benzylic epoxide ethers formed exclusively the four-membered oxetanes, rearrangements of allyl oxiranyl ethers show a selectivity for cyclization to the seven-membered ring. Trialkylsilyl-substituted epoxide allyl ethers also show a preference for the oxepine, and mixtures are obtained as the size of the silyl substituents is increased (Scheme 17). 

The acid-catalysed rearrangement of benzyl phenolic ethers to diphenylmethane compounds and the rates of rearrangement of (Z)-aryUiydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole into (2-aryl-5-phenyl-2H-l,2,3-triazol-4-yl)ureas have been reported. ... 

The first example of a [l,2]-Wittig-type rearrangement was reported in 1924 by Schorigin, and was discovered during studies on the reactivity of benzyl ethers towards alkali metals. Schorigin found that heating a mixture of benzyl ethyl ether (4) with metallic sodium to 130-210 °C generated a small amount (13%) of phenyl ethyl carbinol (5). 

Directed lithiation of aromatic compounds is a reaction of broad scope and considerable synthetic utility. The metalation of arenesulfonyl systems was first observed by Gilman and Webb and by Truce and Amos who reported that diphenyl sulfone is easily metalated at an orf/io-position by butyllithium. Subsequently, in 1958, Truce and coworkers discovered that metalation of mesityl phenyl sulfone (110) occurred entirely at an orf/io-methyl group and not at a ring carbon, as expected. Furthermore, refluxing an ether solution of the lithiated species resulted in a novel and unusual variation of the Smiles rearrangement and formation of 2-benzyl-4,6-dimethyl-benzenesulfinic acid (111) in almost quatitative yield (equation 78). Several other o-methyl diaryl sulfones have also been shown to rearrange to o-benzylbenzenesulfinic acids when heated in ether solution with... 

The Wittig rearrangement is the base-catalyzed 1.2-shift of an alkyl, allyl. benzyl, or phenyl group of an ether from oxygen to carbon. A patent claim describes the conversion of aryl arylmethyl ethers such as 21 into diarylmethanols such as 22.14... 

Photolyses of 31-34 in homogeneous solution results in the formation of diphylethanes 39 (5-15%), phenols 38 (5-15%), ortho-hydroxyphenone 36 (40-60%), and para-hydroxyphenones 37 (20-25%). Small amounts of phenyl benzyl ether 35 (3-8%) were also detected. However, photolyses of all of the four esters on NaY zeolite and Nafion only produce ortho rearrangement products 36. Molecular models suggest that esters 31-34 can enter into NaY zeolite internal surface and the inverse micelle of Nafion. We believe that the preference for formation of ort/zo-hydroxyphenones 36 in the products is a consequence of the restriction on diffusional and rotational motion of the geminate radical pair. 

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