Phenols, reaction with unsaturated

The benzannulation reaction with small alkynes such as 1-pentyne may generate a two-alkyne annulation product. In this case the original [3+2+l]-benz-annulation is changed to a [2+2+1+1]-benzannulation. After CO dissociation and insertion of the first alkyne, the coordinated a,/J-unsaturated moiety in the vinylcarbene complex is supposed to be replaced by the second alkyne. The subsequent reaction steps give the phenol 112 (Scheme 50). 

Theoretical studies also suggest that some of the peroxy radicals formed by addition of 02 to the OH-aromatic adducts may react with NO in competition with cyclization (Andino et al., 1996), generating N02 and an aromatic peroxy radical that may subsequently form phenolic and unsaturated derivatives through reactions with 02 ... 

They react with a solution of bromine in carbon tetrachloride by sub stitution and an equivalent quantity of hydrogen bromide is evolved (compare addition with unsaturated compounds). When the test is conducted with bromine water and a dilute aqueous solution of a phenol, the sign of reaction is the separation of a sparingly soluble bromine substitution product. ... 

Both fumaric and maleic acid give rise to coumarins on reaction with phenols. Initially, this route was considered different from the Pechmann reaction, but experimental evidence has been accumulated which suggests that it is simply a variant (73AJC899). Under the acidic conditions, the unsaturated acid could well produce some malic acid, which would then lose carbon monoxide and water as usual. Generally yields in the two approaches to coumarins are much the same. 

The use of an unsaturated nucleophile to introduce into the chain end of the macromolecule a double bond has also proved successful for the synthesis of poly-THF macromonomers. The oxolane polymerization is started with any efficient initiator. When the growing chains have reached the desired length, the unsaturated deactivator is added. The reaction between the oxonium sites and the nucleophile should be fast and free of side reactions. Various unsaturated nucleophiles have been employed, e.g. p-vinylphenoxide used by Asami50). The THF polymerization was initiated with triethyloxonium tetrafluoroborate and carried out atO °C. Addition of the nucleophile (obtained by reaction of the phenol with NaH) yields the corresponding macromonomer the structure of which was characterized by various techniques ... 

Besides simple enones and enals, less reactive Michael acceptors like /3,/3-disubstituted enones, as well as a,/3-unsaturated esters, thioesters, and nitriles, can also be transformed into the 1,4-addition products by this procedure.44,44a,46,46a The conjugate addition of a-aminoalkylcuprates to allenic or acetylenic Michael acceptors has been utilized extensively in the synthesis of heterocyclic products.46-49 For instance, addition of the cuprate, formed from cyclic carbamate 53 by deprotonation and transmetallation, to alkyl-substituted allenic esters proceeded with high stereoselectivity to afford the adducts 54 with good yield (Scheme 12).46,46a 47 Treatment with phenol and chlorotrimethylsilane effected a smooth Boc deprotection and lactam formation. In contrast, the corresponding reaction with acetylenic esters46,46a or ketones48 invariably produced an E Z-mixture of addition products 56. This poor stereoselectivity could be circumvented by the use of (E)- or (Z)-3-iodo-2-enoates instead of acetylenic esters,49 but turned out to be irrelevant for the subsequent deprotection/cyclization to the pyrroles 57 since this step took place with concomitant E/Z-isomerization. 

The superoxide radical (O ) is another reactive oxygen species. Although the superoxide radical may not react readily with unsaturated fatty acids, it is capable of oxidizing phenolic compounds such as tocopherols, thiols and ascorbic acid (Korycka-Dahl and Richardson, 1980). This, in turn, may lead to earlier oxidation of lipids. However, the significance of superoxide as a pro-oxidant in milk is unclear. Superoxide rapidly dismu-tates in water, yielding hydrogen peroxide which, itself, may be involved in oxidative reactions (Korycka-Dahl and Richardson, 1980) ... 

In several deamination reactions, formation of the hydroxymethyl derivatives 243 (Fig. 90) is frequently reported instead of the expected unsaturated product. Thus, deamination of para-aminomethyl phenols (242, R = p-hydroxyphenyl) produces an intermediate methylenequinonc, which then evolves to hydroxymethyl phenol by reaction with water, - whereas deamination of aminome-thane sulfonates (242, R = SO Na) proceeds through an Sn2 attack by water on the zwit-terionie form of the Mannich base to yield the hydroxylated derivative. - "... 

In the preparation of mixed aliphatic ethers, the reaction between alcohol and olefin is catalyzed by dilute sulfuric acid. Those olefins that can be derived from tertiary alcohols are the most suitable, e.g., isobutylene and trimethylethylene, leading to tertiary alkyl ethers. Also, primary alcohols are more suitable as additives than secondary alcohols tertiary alcohols are practically non-reactive. The procedure, typified by the preparation of ethyl i-amyl ether (90%), is not as rapid and convenient as the dehydration reaction discussed above (method 118). Phenols have been condensed In the cold with unsaturated compounds under the influ-... 

Phenolic resins are well known for their contribution in improving hardness, gloss, and water and chemical resistance in oleoresinous varnishes. Those based on p-alkyl-substituted phenols and with heat-reactive methylol groups have also been incorporated into alkyd resins. The reaction has not been well smdied. Presumably, the methylol group would react with the unsaturation functionality on the fatty acid chain to form the chroman stmcture, similar to what is believed to have occurred in the varnish. Etherification between the methylol group and free hydroxyl of the alkyd resin, catalyzed by the residual acidity in the resin, would be another possible reaction. 

Electrolysis of benzothiete sulfone 269 yields the phenylmethanesulfinate anion (major) and the o-toluenesulfinate anion (minor).Thermolysis 618,619 gj. photolysis of thiete 1,1-dioxides proceeds via ring-opening to vinyl sulfines, for example. 288, which have been trapped by reaction with water, phenol,methanol, or norbornenes. These intermediates may recyclize to unsaturated sultines (cyclic sulfinate esters) (e.g., 289) or lose sulfur monoxide to give mainly the trans isomers of a,j3-unsaturated carbonyl compounds (e.g., 290). Mass spectra also indicate the formation of unsaturated sultines. ... 

In the Dotz reaction, an unsaturated chromium carbene complex is combined with an alkyne to give a substituted phenol. The unsaturated group may be an alkenyl, cycloalkenyl, or aryl group. There is almost always a methoxy or other alkoxy group attached to the carbene. 

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