Reaction with amino phenols

Phenol concentration. When phenol is used to preserve a vaccine its concentration must not exceed 0.25% wA or, in the case of some vaccines, 0.5% w/v. Phenol is estimated by the colour reaction with amino-phenazone and hexacyanoferrate. 

The poly-phenols or poly-hydroxy benzenes are obtained from the dry distillation products of wood. The methods of synthesis are in general those for the mono-phenols though the diazo reaction does not usually work well with amino phenols. Also some of the methods of preparation used for poly-phenols do not apply to the mono-phenols. In general properties they resemble the mono-compounds, but they are usually more easily soluble in water, react more readily and are characterized by their strong reducing properties. 

The above route also proved to be economically less viable, therefore, we decided to use the commercially available p-amino phenol to carry out a similar set of reactions. p-Amino phenol was condensed with dimethoxy tetrahydrofuran to obtain the i -aryl pynole 41. The phenol 42 was converted to the acetate and that was subjected to die Vilsmeier/Friedel-Crafts acylation conditions to obtain the aldehyde 43. Decarbonylation of the aldehyde followed by Wolff-Kishner reduction and esterification resulted in the formation of con imd 45. Similar results were obtained starting with p-anisidine. In this case demethylation was carried out using boron tribromide. The phenolic group... 

Stiixe and coworkers (90—93) have condensed appropriately substituted quinones with amino-phenols to yield isolable, single-stranded intermediates which may be converted to ladder structures by treatment at higher temperature. Alternatively, the reaction may be carried out at high temperature in a polar, aprotic solvent such as hexamethyl phosphor-amide (HMP) to 3deld the ladder poljmer directly. 

The reaction between 3,5 dinitrobenzoyl chloride and compounds containing the OH, NHj, or NH groups is very rapid, and therefore is particularly suitable for identification purposes cf. pp. 335, 338, 381). It is usual to have sodium hydroxide present during the reaction with phenols and amino-acids, but this is not necessary with alcohols if they are dry. 

Although phenols have not participated in the Conrad-Limpach reaction under certain conditions thiophenols were not as innocent. Lee and coworkers reported mixtures of thiochromenones and quinolones from reactions of amino-thiophenols with ethyl benzoyl acetate. Amino-thiophenol 67 reacted with ethyl benzoylacetate 68 in PPA to give a mixture of thiochromenone 70 and quinolone 69 in which the quinolone predominated. 

Reaction of dibenzylamine with ethylene oxide affords the amino alcohol, 82. Treatment of that product with thionyl chloride gives the a-sympathetic blocking agent, dibenamine (83). (Condensation of phenol with propylene chlorohydrin (84) gives the alcohol, 85. Reaction with thionyl chloride affords the chloride (86). Use of the halide to alkylate ethanolamine affords the secondary amine (87). Alkylation of this last with benzyl chloride... 

Since a small amount of water is always present in novolac resins, it has also been suggested that some decomposition of HMTA proceeds by hydrolysis, leading to the elimination of formaldehyde and amino-methylol compounds (Fig. 7.15).42 Phenols can react with the formaldehyde elimination product to extend the novolac chain or form methylene-bridged crosslinks. Alternatively, phenol can react with amino-methylol intermediates in combination with formaldehyde to produce ortho-or para-hydroxybenzylamines (i.e., Mannich-type reactions). 

As in the case of benzimidazole, a parallel synthesis of benzoxazoles was described. The authors report that mixing directly differently substituted o-amino phenols 193 with acylating agents 194 and heating at 200 °C for 10-15 min under microwave irradiation, a collection of benzoxazoles 195 was obtained (Scheme 70). With this reaction, a 48-member library of benzoxazoles with different substituents on the aromatic rings was obtained [125]. 

For the synthesis of coumarins, the Pechmann reaction [145] is one of the most popular synthetic routes. As the reaction is conventionally carried out at high temperature, two microwave-assisted versions have been recently described. Besson and co-workers described the cyclocondensation of different m-amino phenols 226 with /1-ketoesters 227 on graphite/montmorillonite KIO support (Scheme 83). The use of graphite was crucial in the development of the reaction conditions. In fact, microwave irradiation of the reagents using different conditions gave poor results in terms of yields and purity. The optimized conditions, using a monomode microwave system, employed... 

Most aromatic difunctional reagents react with N3P3Cl6 to afford spirocyclic products (20,176,180,181,189,190). With catechol, the trispiro product is observed (190). This product was shown to function as a host in the formation of several inclusion adducts, including polymers (191). Ring degradation of the cyclophosphazene ring occurs in the reaction with o-amino phenol as well as in the reaction with catechol in the presence of a triethylamine (192). 

The hydrochloride of 3-amino-4-hydrazinopyridine 65 was prepared by reaction of the 4-chloro-3-nitropyridine derivative with ethoxycarbonyl-hydrazine in phenol to give the hydrochloride of ethyl 3-(3-nitro-4-pyridyl)carbazate 64 (R2 = OEt), which on successive heating in concentrated hydrochloric acid and hydrogenation over Pd/C gave 65. Its reaction with phenylacetic acid or with phenoxyacetic acid gave the hydrochloride... 

Still unexplained are the reactions, with periodate, of hydroxy phenols and certain oxygenated aromatic compounds,1 as well as of some a-amino acids not containing the 2-hydroxyamine structure.8... 

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