Phenol effect

Hydroxythioxanthones are readily obtained with good regioselectivity from the reaction of thiosalicylic acid with phenols effected by a mixture of methanesulfonic acid and alumina (Equation 189) <2004S2900>. 

Arylchrom-3-en-2-ols and 3-arylcoumarins are accessible from 3,3-diethoxyprop-l-yne through sequential Pd-catalysed coupling with aryl halides and hydroarylation and finally cyclisation <97SL1367>. A facile cyclisation of o-(3-hydroxy-3-methylbutynyl)phenols effected by BBr3 leads to 4-bromo-2,2-dimethylchromenes the bromine can be removed by electrolytic reduction <97H(45)1131>. 

The substituent effect on the reaction energies of the phenoxy abstraction is remarkably large, even though we can deduce from the benzyl abstraction that the substituent effect on the PPE radical is small. Analysis of the substituent effects on phenol and phenoxy [91] shows that the phenoxy radical is stabilized and phenol is destabilized by the methoxy substituents. The phenoxy and phenol effects are additive, resulting in a large total substituent effect for the a- and /3-channels. 

ABSTRACT. Selective formylation of phenol at the 4-position is achieved by using 3-cyclodextrin as catalyst in the reaction of phenol with chloroform in aqueous alkali. The reactions of 1,3-dihydroxybenzene and indol, respectively, in the place of phenol give 2,4-dihydroxybenz-aldehyde and indole-3-aldehyde in virtually 100% selectivies and high yields. The reactions of para-substituted phenols, 4-methylphenol and 5,6,7,8-tetrahydro-2-naphthol, instead of phenol, effect the selective dichloromethylation at the para-positions. Selective carboxylation of phenol at the 4-position is achieved in the reaction of phenol with carbon tetrachloride in aqueous alkali by using 3-cyclodextrin and copper powder as catalyst. 

Phenols Effective on cellular membranes and bacterial walls... 

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