Polycyclic phenols

A one-pot procedure [9] based on the cycloaddition of 4-aryl-2-silyloxybuta-dienes 7 and bisdiene 8 with alkynes, followed by oxidative aromatization of the cycloadducts, opened a route to polycyclic phenols without isolating the cyclo-hexadiene derivative intermediates (Scheme 2.5). 

Aromatic amines, such as phenyl- -naphthylamine or condensation products of diphenylamine with acetone condensates, are excellent antioxidants and antiozonants but cause color development. From the sterically hindered phenols, monocyclic phenols, such as 2,6-di-teit-butyl-p-cresol, are less effective antioxidants but remain white and nontoxic during aging. They are, however, volatile and provide poor protection at elevated processing temperatures. Polycyclic phenols, such as 2,2 -methylene-bis (4-methyl-6-teit-butylphenol), are relatively nonvolatile, but become discolored by oxidation to a conjugated system. O Shea... 

Cterically hindered phenols are used widely today as effective non- discoloring, nonstaining antioxidants for hydrocarbon systems, particularly rubbers and plastics. These compounds may be grouped in two broad classifications—monocyclic phenols represented by a compound such as 2,6-di-fer -butyl-4-methylphenol (I) and polycyclic phenols such as 2,2 -methylenebis(4-methyl-6-terf-butylphenol) (II). (Throughout this chapter, X represents tert-butyl). 

The polycyclic phenols, being somewhat more effective and relatively nonvolatile, afford good protection at both ambient and elevated temperatures. This improvement in activity, however, is generally accompanied by a sacrifice in color. For methylenebisphenols the discoloration may be caused by oxidation products of the antioxidant in which a highly conjugated system is developed. For example, Kharasch and Joshi (7) found that a purple color developed when oxygen was bubbled through an alkaline alcoholic solution of 4,4 -methylenebis(2,6-di-fert-butylphe-nol), III, a commercial antioxidant. They showed that this color was caused by the anion, V, of a quinonemethide type oxidation product, IV, of the phenol. 

Phloroglucinol (= 1,3,5-Benzenetriol) (phenolic) Protocatechuic acid (phenolic) Pseudohypericin (polycyclic phenolic)... 

When benzo[ ]furan derived polycyclic phenol 84 was allowed to react with bromine, tribromide 85 was formed in high yield (Equation 65) <1999JME3199>. Reaction of 2-methylbenzo[ ]furan 86 with Wbromosuccinimide (NBS) at room temperature gives 3-bromo-2-methylbenzo[. ]furan 87 as illustrated in Equation (66) <2005JOC10323>. 

Polycyclic phenols. Polycyclic aromatic ketones such as 1 can be converted into phenols by dehydrogenation of the corresponding enol acetates with o-chloranil... 

Phthalimide-N-sulfenyl chloride, 375 Phthaloylamino acids, 212 Phthaloyl-L-valine, 212 Phytuberin, 197 Phytyl chloride, 499, 500 Picrotoxinin, 265, 430 Pictei-Spengler cyclization, 308 Pinacol-typc reduction, 513 -Pinene, 346, 367 Piperidine acetate, 318 Piperidinium acetate, 375-376 Polonovski reaction, 484 Polyaminolactams, 378-379 Polycyclic phenols, 102 Polyene cyclization, 291-292 Polyethylene glycols, 360, 376 Polyketides, 302 Polyphosphate ester, 376-377 Polyprenylation, 499-500 Potassium-Ammonia, 273, 377 Potassium-t-Butylamine-18-Crown-6, 377-378... 

Polycyclic phenolic humic substances produce phenol carboxylates (oxidation of adjacent rings) of the salicylate type and possibly 3-ketoenolates (El(L) = -0.08 V for both acac" and sal2 )... 

Hydriodic acid reduces some esters of polycyclic phenols. 7-Acetoxybenz[a]anthracene and 7,12-diacetoxybenz[a]anthracene are converted to benz[a]anthracene on refluxing with hydriodic acid and acetic acid (equation 73). On the other hand, 9-acetoxyphenanthrene is not reduced, but hydrolyzed to 9-hydroxyphenanthrene. ... 

Treatment of ketone 409 with lithium diisopropylamide (LDA) results in the ethyl 1,2-dihydroxybenzoate 410 in a 74% yield (equation 191) . The acid-catalyzed isomerization of diarene oxides derived from benz[a]anthracene, chrysene and benzo[c]phenanthrene gives mixtures of isomeric polycyclic phenols. Finally, it should be mentioned that dibenzo[i>, ]oxepin 411 undergoes an interesting rearrangement to 2-hydroxyphenylindene 412 (equation 192). 

Polycyclic phenols, keto-enol tautomerism in 719-721 Polygalaceae 967... 

Synthesis of Polycyclic Phenols containing unsaturated and saturated rings bearing heteio atoms... 

A number of bicyclic and polycyclic phenols have been prepared invariably from cycloaliphatic intermediates and these have been classified in this section which essentially describes alkenylphenol derivatives. 

Naphthalenol a-Naphthol Oxidation base 33 Classification Polycyclic phenol Empirical CioHjO Formula C10H7OH... 

Very recently, Sasai and co-workers further realized the asymmetric oxidative coupling of polycyclic phenols such as 2-anthracenol, 9- or 3-phenan-throl, and 5-chrysenol by dinuclear vanadyl complexes (S,S,/ a)-31, (S,S,/ a)-32, or their mononuclear analog (S)-33 (Scheme 3.12). It should be noted that, apart from the corresponding axially chiral biaryl products obtained in up to 93% ee, no over-oxidation side product was observed. 

Scheme 3.12 V-catal3 ed asymmetric oxidative coupling of polycyclic phenols reported by Sasai.

CAS 92-44-4 EINECS/ELINCS 202-156-7 Synonyms 2,3-Dihydroxynaphthalene Classification Polycyclic phenol Empin cal C10H8O2 Formula CioH6(OH)2... 

Classification Polycyclic phenol Empirical C10H8O2 Formula CioH6(OH)2... 

This chiral copper(ll) complex was also effective in the oxidative cross-couplings between two electronically different polycyclic phenols, generally giving good yields and high enantioselectivity [42]. 

Apart from cinnamoyl esters, aromatic amino acids (see Chap. 5.1) and the alcohols corresponding to the common hydroxycinnamic acids, as well as some glycerolaryl compounds, are of interest in connection with the biosynthesis of lignin and other polycyclic phenolic compounds. 

Butyl rubber formulations are cured with polycyclic phenol-formaldehyde resins having di methylene ether bridges and methylene bridges, the molar ratio of dimethylene ether bridges to methylene bridges being less than about 2.5 1. They display improved heat ageing characteristics. 

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