Elbs hydroxylation

The semi-direct 5-hydroxylation of pyrimidines by the Elbs persulfate reaction is summarized in Section 2.13.2.1.5a. 

The hydroxylation of a phenol 1 upon treatment with a peroxodisulfate in alkaline solution, to yield a 1,2- or 1,4-dihydroxybenzene 3, is called the Elbs reaction The phenol is deprotonated by base to give a phenolate anion 4, that is stabilized by resonance, and which is activated at the ortho or the para position towards reaction with an electrophilic agent ... 

Another hydroxylation reaction is the Elbs reaction In this method, phenols can be oxidized to p-diphenols with K2S20g in alkaline solution. Primary, secondary, or tertiary aromatic amines give predominant or exclusive ortho substitution unless both ortho positions are blocked, in which case para substitution is found. The reaction with amines is called the Boyland-Sims oxidation. Yields are low with either phenols or amines, generally under 50%. The mechanisms are not clear, but for the Boyland-Sims oxidation there is evidence that the S20 ion attacks at the ipso position, and then a migration follows. ... 

Hydroxypyridine and pyridin-2-one are sufficiently reactive to undergo Elbs oxidation, and in both cases the substituent directs hydroxylation mainly para (Scheme 40) (58JA3717). Quinoline may be converted into 3-hydroxyquinoline (6% yield) by Udenfriend oxidation (ascorbic acid and oxygen in the presence of iron(II)) which is believed to involve attack by OH+ rather than radicals (54JBC(208)74i). 

Hydroxylation of arylamines with persulfate ion, or Boyland-Sims oxidation, gives ortho-substituted aminophenols in good yields [29]. As with the Elbs oxidation, the procedure is also carried out in two steps - first, treatment with the oxidant to obtain an aminophenyl sulfate ester and, second, hydrolysis to obtain the final product. Primary, secondary and tertiary amines can all be used in this reaction. The ortho product is formed, except when no ortho-positions are available, which leads to para-substitution. Electrophilic attack on the ipso-carbon is believed to be the most likely mechanism, although minor radical pathways also seem to be present. 

A number of other aromatic oxidations involving peroxygen species have been documented. Probably the best known of these is the hydroxylation of phenols using alkaline peroxydisulfates, known as the Elbs reaction.490 This... 

The oxidation of phenol with potassium persulfate (K2S2O8) in an alkaline medium to p-hydroquinone is known as the Elbs persulfate oxidation. Elbs used ammonium persulfate for the oxidation of 2-nitrophenol (7.42) to 2-nitro-p-hydroquinone (7.43), but the potassium salt is commonly used for the hydroxylation of phenols. 

Elbs persulfate oxidation. Hydroxylation of phenols to p-diphenols by potassium persulfate in alkaline solution. 

Polymerizable 2(2-Hydroxyphenyl)2H-Benzotriazole Ultraviolet Stabilizers. Synthesis. Some of the most important ultraviolet stabilizers belong to the class of 2(2-hydroxyphenyl)2H-benzotriazoles. Ever since the early work on benzotriazoles by Elbs (25,24), a number of 2(2-hydroxyphenyl)2H-benzotriazoles [2H-benzotriazole-2-yl)2-hydroxy-benzene] have been prepared (25). Even some polymerizable compounds of this class had been synthesized. The benzotriazole stabilizing groups had in the past been attached to a polymerizable group via a phenolic hydroxyl group placed in the benzotriazole ring (26). 

Persulfate Replacement of hydrogen by hydroxyl Elbs oxidation s. 1,131 SgOg- H —OH... 

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