Phosphotungstic acid as an efficient solid catalyst for intramolecular rearrangement of benzyl phenyl ether to 2-benzyl phenol

Solid Acid Catalysts: Modification of Acid Sites and Effect on Activity and Selectivity Tuning in Various Reactions

“…Solvent studies showed that the conversion of BPE was as low as 15% for acetonitrile and the reaction did not proceed in THF and MeOH indicating that the solvated benzyl cations spontaneously reacted with the phenoxide ion due to the faster recombination process. In order to ascertain the role of the solvent in the rearrangement reactions, a neat reaction with 0.1% mole of DTP was carried out, which gave a 2-BP selectivity which was 50% less than that obtained in the presence of a solvent with a major formation of a side product, dibenzylated phenol [5].…”

“…Several solid acids such as clays, zeolites, heteropoly acids, mesoporous materials and resins are widely used as catalysts for many organic transformations [1]. Among the various organic transformations, hydroxyalkylation of phenols to the corresponding bisphenols (dihydroxydiarylmethanes, DAM), intramolecular rearrangement of benzyl phenyl ether (BPE) to 2-benzyl phenol (2-BP) and selective cleavage of tertbutyldimethylsilyl ether (TBDMS) into the corresponding alcohol are industrially important reactions [2][3][4][5][6][7][8]. The end products of such reactions (e.g.…”

Acidic rearrangement of benzyl group in flavone benzyl ethers and its regioselectivity

“…The method of the oxidative cyclization of 2 0 -hydroxychalcone was selected to build the flavone skeleton [1,17]. The method with trifluoroacetic acid or methylsulfonic acid under heat-refluxing conditions of the rearrangement reaction of the benzyl group was selected [12,[18][19][20]. However, this method required a long reaction time-at least 48 h. Thus, we applied microwaves and found that it significantly shortened the reaction time to less than 30 min.…”

Phosphotungstic Acid Catalysed Synthesis of β-Enamino Compounds under Solvent-Free Conditions

“…8 In particular, the Keggin-type HPAs such as H 3 (SiW) are the most efficient catalysts for a variety of catalytic processes for industrial application. 9 PW is considered to be the strongest heteropoly acid in the Keggin series. It has been reported to be an efficient catalyst for many important organic transformations, including the intramolecular rearrangement of benzyl phenyl ether to 2-benzyl phenol, 9 the Beckmann rearrangement, 10 the Fries rearrangement, 11 the synthesis of 1,1-diacetates, 12 b-acetamido ketones, 13 diaryl sulfoxides, 14 diisobornyl ether, 15 1,3-dioxolane derivatives, 16 5-alkoxycarbonyl-4-aryl-3,4-dihydropyrimidin-2-ones, 17 quinaldines and lepidines, 18 the diacetal of pentaerythritol, 19 3, 4-dihydropyrimidin-2(1H)-ones 20 and a-amino phosphonates.…”

“…9 PW is considered to be the strongest heteropoly acid in the Keggin series. It has been reported to be an efficient catalyst for many important organic transformations, including the intramolecular rearrangement of benzyl phenyl ether to 2-benzyl phenol, 9 the Beckmann rearrangement, 10 the Fries rearrangement, 11 the synthesis of 1,1-diacetates, 12 b-acetamido ketones, 13 diaryl sulfoxides, 14 diisobornyl ether, 15 1,3-dioxolane derivatives, 16 5-alkoxycarbonyl-4-aryl-3,4-dihydropyrimidin-2-ones, 17 quinaldines and lepidines, 18 the diacetal of pentaerythritol, 19 3, 4-dihydropyrimidin-2(1H)-ones 20 and a-amino phosphonates. 21 It also catalyses the N-t-butoxycarbonylation of amines, 22 the chemoselective oxathioacetalisation of carbonyl compounds, 23 trimethylcyanosilylation reactions of aldehydes and ketones, 24 and the Michael addition reaction of thiols to a,b-unsaturated ketones.…”