Benzyl phenolic ethers, rearrangement

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. ... 

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... 

The diphenolic protoberberine methobromide 285 derived from 283 was refluxed in aqueous ethanolic sodium hydroxide for 12 hr to furnish the quinomethide 287 in 92% yield (Scheme 50). Compound 287 was treated with dimethyl sulfoxide to give rise to the desired diphenolic ochotensimine analog 288 through enolization (150,151). The presence of the phenolic hydroxyl group is essential in this rearrangement because the benzyl ether (284) was recovered unchanged under the same alkaline conditions. 

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. 

Unlike the synthesis of phenols from non-aromatic sources that of thiophenol by similar methodology is virtually unknown. The synthesis shown of the diacetate of a tricyclic compound containing an o-substituted thiophenol system would appear to be applicable to the simpler central portion and to bicydic analogues. Ethyl 4-(1-benzyl-2-thioxo-pyrrolidin-3-yl)-5-(diazoacetyl)-pyrrole -2-carboxylate in dichloromethane was treated with boron trifluoride etherate in the same solvent and after 15 mins, the intermediate shown resulted which in a sealed tube (under vacuum) with acetic acid/acetic anhydride (3 1) at 132°C during 90mins. produced by a Pummerer rearrangement, ethyl... 

Refluxing acetylated glycals with phenols in chlorobenzene without any acid catalyst gives the usual 0-linked rearranged compounds as o/p-mixtures. Use of phenols with NO2 and Bu substituents allows for easy crystallization of pure a-anomers and consequently multigram quantities of these products can be made. The products are readily deacetylated and converted to 0-benzyl ether derivatives. ... 

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