O- Aminophenols

Place 170 ml. of concentrated sulphuric acid in a 1-litre three necked flask provided with a stirrer, and add 112 - 5 g. of o-aminophenol, followed by 287 g. of glycerol maintain the temperature below 80° by cooling, if necessary. Keep the mixture in a fluid state by placing the flask on a steam bath. 

Supplement (combined 1933 1740-1928 zidine, 314. Triamines, 294. Hydroxy-amines o-Aminophenol, 354. 

Bis(benZoxaZol-2-yl) Derivatives. Bis(benzoxazol-2-yl) derivatives (8) (Table 3) aie prepared in most cases by treatment of dicaiboxyhc acid derivatives of the central nucleus, eg, stilbene-4,4Cdicarboxyhc acid, naphthalene-l,4-dicarboxyhc acid, thiophene-2,5-dicarboxyhc acid, etc, with 2 moles of an appropriately substituted o-aminophenol, followed by a ring-closure reaction. These compounds are suitable for the brightening of plastics and synthetic fibers. 

Both 5-hydroxyquiQoline [578-67-6] and S-hydroxyquiaoline [148-24-3] have been prepared ia good yields by the acid hydrolysis of the appropriate aminoquiaoline at temperatures of 180—235°C (124). The latter compound has been prepared ia several different ways, including sulfonation-fusion of quiaoline. Hydrolysis of 8-chloroquinoline [611-33-6] gives a 93% yield, whereas 80% is obtained ia a modified Skraup synthesis with o-aminophenol (125,126). 

An interesting preparation of substituted o-aminophenols has been developed by Birkofer and Daum (30). 2-Acylfurans (8) plus an aliphatic secondary amine presumably condense to give the eorresponding enamine (9) (not isolated), which undergoes thermal isomerization to the o-amino-phenol (10). 

The formation of enamines from carbonyl compounds and secondary amines usually entails as only questionable structural feature, the possible isomeric position of double bonds in the product. Molecular rearrangements have not presented synthetic limitations. A notable exception is the generation of o-aminophenols on distillation of enamines derived from 2-acylfurans 620,621). 

The method developed for preparation of telluradiazines 89 was applied to the synthesis of benzo derivatives of l-oxa-2-tellura-6-azacycloocta-3,5-diene 100 (99UP2). It involves dehydrobromination of bromotellurenylvinylaldimines 101, obtained by condensation of 2-methyldibromotellurocyclohexenealdehyde with o-aminophenols. Under a treatment of benzene suspension of 101 with triethyl-amine followed by short-term refluxing the reaction mixture the heterocycles 100 were obtained in 71-87% yields. 

Aminophenols (underivatized) o-aminophenol, p-aminophenol, and acetanilide 30 m DB-1701 column, 45-250° at 107min. 

Snznki H, Y Fnrnsho, T Higashi, Y Ohnishi, S Horinonchi (2006a) A novel o-aminophenol oxidase responsible for formation of the phenoxazinone chromophore of grixazone. J Biol Chem 281 824-833. 

The CO-transfer reaction onto o-aminophenol or o-phenylenediamine by GDI has been used as a method for converting /Mactam carbanilides, obtained by a 4-component condensation, into the corresponding carboxylic acids without damaging the sensitive fi-lactam moiety. The method has its basis in the production of easily cleavable compounds from o-hydroxy- and o-aminoanilides and CDI [76]... 

Oxazole. DaB nicht nur NH2-, sondem auch phenolische OH-Gruppen mit s-Triazin zu reagieren vermogen, laBt sich an dem zu Benzoxazol (XLI) ftihrenden RingschluB des o-Aminophenols demon-strieren (25). 

Those polyester FBAs containing a benzoxazole group are usually prepared from the appropriate o-aminophenol and carboxylic acid (11.45 Y = OH) or one of its derivatives, as shown in Scheme 11.10. The reaction proceeds via an intermediate amide and it can be advantageous to start from an acid derivative such as the acid chloride (11.45 Y = Cl) or ester (11.45 Y = OEt), which are both more effective acylating agents. The preparation of compound 11.36, shown in Scheme 11.11, illustrates this process, but the optimum conditions for ring closure vary considerably from one structure to another. The article by Gold contains a valuable and detailed summary [4]. 

An interesting observation was made when o-aminophenol (2-411) was employed in the reaction with carbethoxypiperidone 2-410 and acrolein (Scheme 2.98). In this case, the spirocydic scaffold 2-412 was exclusively formed in 67% yield. This result can be explained by invoking a stereoelectronic control due to the presence of the aromatic ring which prevents the formation of the corresponding fused tetracyclic isomer. Moreover, both reactive sites can simultaneously be functionalized using 2-amino-1,3-propanediol (2-413) as partner in the multicomponent reaction. This leads to the formation of three new cycles... 

Oxidation of the tetrahydroindolizine 338 with sodium chlorite gives the lactam 339, which rapidly lactonizes to give the pyranoindolizine 340 (Equation 122) <2001T8647>, and the one-pot , three-component reaction between the keto ester 235, acrolein, and o-aminophenol (formally analogous to that of Equation 63) gives the benzoxazolo-naphthyridine 341 (Equation 123) <20010L2145>. 

Z. Zhang, H. Liu, and J. Deng, A glucose biosensor based on immobilization of glucose oxidase in electropolymerized o-aminophenol film on platinized glassy carbon electrode. Anal. Chem. 68, 1632-1638 (1996). 

The pyrazolotriazinecarboxylate 708 underwent cyclization with urea or thiourea to give (84PHA432) pyrazolopyrimidinotriazines 711, and with o-phenylenediamine, p-chloroaniline, or o-aminophenol to give quinolino-pyrazolotriazines 710. The reaction of the pyrazolo[5,l-c][I,2,4]triazine 709 with hydrazine hydrate gave 712, and its reaction with phenyl isothiocyanate gave 713 (83G219). 

The reaction of 718 with o-aminophenol hydrochloride gave (87JHC1805 88JHC1259) 9-ethoxycarbonyl-6-oxo-5,6-dihydropyrazolo-[1, 5 3,4][l,2,4]triazino[5,6-fe][l,5]benzoxazepine 725, whose alkyla-... 

Reactions of 4-aminofurazan-3-carboxylic acid iminoester 122 with o-aminophenol, phenylenediamine, ethylene-diamine, and aminoethanol give compounds 123-126 (Scheme 33) <2002RJ0872>. 

Cyclization, 2-mercaptobenzoxazole from o-aminophenol, 30, 57 methyl cyclopropyl ketone from 5-chloro-2-pentanone, 31, 74... 

This intramolecular etherification approach has successfully been applied to the syntheses136 of siccanin137 and clusifoliol,136 and a formal synthesis of morphine.138 Examples of tandem inter- and intramolecular etherification reactions have also been reported which convert catechol and o-aminophenol derivatives into benzodioxins (Equation (24)),139-141 benzodioxepines,142 and morpholines.139,140... 

Arylbenzoxazoles were prepared by Pd-catalyzed three-component condensation of aryl halides with o-aminophenols and carbon monoxide followed by dehydrative cyclization [24], A variant of such methodology using o-fluorophenylamines in place of o-aminophenols was used to synthesize arylbenzoxazoles [25]. 

Reaction of 2-mercaptomethyl-l,3,4-oxadiazolin-5-one 321 with o-aminophenol 322 and glycine, in refluxing isopropanol, gives 3-mercaptomethyl-[l,2,4]triazole[3,4-A benzoxazole 71, via intermediate 323 (Scheme 31), and 3-mercaptomethyl-6-oxo-oxazolo[2,3-c][l,2,4]triazole 324, respectively <1996M549>. 

Mamyama et al.25 have obtained high-molecular-weight poly(benzoxazole)s by the low-temperature solution polycondensation of A,A 0,0 -tetrais(trimethyl-silyl)-substituted 2,2-bis(3-amino-4-hydroxyphenyl)-l,l,l,3,3,3-hexafluoro-propane (25) with aromatic diacids and subsequent thermal cyclodehydration of the resulting poly(o-hydroxy amide)s in vacuo. In this method, aromatic diamines with low nucleophilicity are activated more positively through the conversion to the /V-silylated diamines, and the nucleophilicity of the fluorine-containing bis(o-aminophenol) can be improved by silylation. 

The spirophosphorane (74) has been identified as an intermediate in the formation of (75) from o-aminophenol and trisdiethylaminophosphine.61 With ethylene glycol (75) gave high yields of the phosphoranes (76) and (77). As expected, the phosphoranes (78) have apical fluorine atoms.52 The interesting bicyclic phosphoranes (79) and (80) have been prepared as shown.63... 

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