Tri hydroxy benzenes

The reaction is not practical for the preparation of phenol itself, but is used in the case of the tri-hydroxy benzene pyro-gallol or pyro-gallic acid, which is obtained by heating gallic acid, which is tri-hydroxy benzoic acidj as above. 

I ogaUol.—Pyrogallol, the vicinal or 1-2-3-tri-hydroxy benzene, is also called pyro-gallic acid as it is obtained by heating gallic acid which is a mono-carboxy tri-hydroxy benzene. 

Constitution. Tautomerism.—The constitution of each of the poly-phenols which we have considered has not been taken up because it has been sufficiently established by the syntheses and reactions as given. In the case of phloroglucinol, however, we have another case of tautomerism. Its constitution as tri-hydroxy benzene is established by the syntheses given for it and the fact that it yields tri-acyl derivatives. Toward other reagents, however, it acts otherwise than as a hydroxyl compound. Hydroxylamine, H2N—OH, which is the characteristic reagent for aldehydes and ketones (p. 124), yields a... 

Gallic Acid.—The 3-4-5-tri-hydroxy benzoic acid is known as gallic acid. The proofs of this constitution are (i) that on heating with lime and the loss of carbon dioxide we obtain p3rrogallol which has been proven to have the constitution i-2-3-tri-hydroxy benzene (p. 619) and (2) that it may be synthesized from either brom-protocate-... 

Also phloroglucinol the 1-3-5-tri-hydroxy benzene may have the tautomeric constitution of a tri-ketone (p. 621) in which case it is a tri-oxy derivative of hexa-hydro benenze. 

Similarly, application of phosphotungstic acid has also been employed in the reaction of di- and tri-hydroxy benzenes with ethyl acetoacetate. The reactions were... 

This proof is exactly analogous to that for the constitution of pseudocumene, 1-3-4-tri-methyl benzene from either meta-xylene or para-xylene (p. 490). That the two hydroxyls are ortho to each other is proven by the fact that on heating with lime protocatechuic acid yields p3rrocatechinol, 1-2-di-hydroxy benzene. 

A soln. of 3/ -acetoxy-17-hydroxyalloeholanic acid lactone- (24- -17) in benzene dropped into an ethereal soln. of methyl-Mgl, and refluxed 6 hrs. on a water bath with continuous stirring —v 3/ ,17,24-tri-hydroxy-24,24-dimethylallocholane. Y 75%. (J. R. Billeter and K. Miescher, Helv. 32, 564 (1949).)... 

Preparation by alkylation of 2,2, 4-tri-hydroxy-benzophenone with 2-methyl-pentene in benzene in the presence of concentrated sulfuric acid [835]. 

Obtained (poor yield) by reaction of DDQ with 2,4,6-tri-hydroxy-3-(3-methyl-2-bute-nyl)isobutyrophenone in refluxing benzene for 20 min (3%) [8138]. 

The vapor-phase pyrolysis of 4-hydroxy-1,2,3-triazole and its iV-methyl derivative affords methan-imine and its A-methyl analog. Analysis of the reaction path by the MNDO method shows the presence of two stable or metastable isomers, (liif)-4-hydroxy-l,2,3-triazole and its ketone protomer <89NJC551>. 4-Diazo-1,2,3-triazoles (122) thermolyze or photolyze in benzene to 4//-l,2,3-tri-azolylidenes (123) which convert benzene to 4-phenyl-1,2,3-triazoles and/or isomerize to a-diazo-nitriles (124). Intermediates (124) react with benzene via a carbene to give addition, ring expansion or substitution products (Scheme 17) <82TL5115>. The similar thermolysis of diazotriazoles in substituted benzene gives complex mixtures in which all of the components are sometimes impossible to isolate and identify <90AHC(48)65>. 

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