O-Phenylenediamine, Reaction

The partially reduced compound 42 was prepared by reaction of the bisoxime 41 with o-phenylenediamine. Reaction of the quinoxalinyl esters 43 with primary amines has given a variety of 2-substituted-1,2-dihydro-l-oxo derivatives (44).It is not clear if the reaction with hydrazine gave the 2-amino compound 44 (R = NH2) or the diazepino compound 45. ... 

This important oxidation - reduction indicator is readily prepared by a double Skraup reaction (compare Section V,l) upon o-phenylenediamine ... 

Because of the time and expense involved, biological assays are used primarily for research purposes. The first chemical method for assaying L-ascorbic acid was the titration with 2,6-dichlorophenolindophenol solution (76). This method is not appHcable in the presence of a variety of interfering substances, eg, reduced metal ions, sulfites, tannins, or colored dyes. This 2,6-dichlorophenolindophenol method and other chemical and physiochemical methods are based on the reducing character of L-ascorbic acid (77). Colorimetric reactions with metal ions as weU as other redox systems, eg, potassium hexacyanoferrate(III), methylene blue, chloramine, etc, have been used for the assay, but they are unspecific because of interferences from a large number of reducing substances contained in foods and natural products (78). These methods have been used extensively in fish research (79). A specific photometric method for the assay of vitamin C in biological samples is based on the oxidation of ascorbic acid to dehydroascorbic acid with 2,4-dinitrophenylhydrazine (80). In the microfluorometric method, ascorbic acid is oxidized to dehydroascorbic acid in the presence of charcoal. The oxidized form is reacted with o-phenylenediamine to produce a fluorescent compound that is detected with an excitation maximum of ca 350 nm and an emission maximum of ca 430 nm (81). 

The more traditional methods of phenazine synthesis falling into the type A synthesis are altogether less satisfactory than the application of the Beirut reaction. Traditionally, Ris prepared phenazine in low yield by heating o-phenylenediamine and catechol in a sealed tube at 200 °C (1886CB2206) however, the method appears to be unsatisfactory at best and gives, in addition to phenazine, 5,10-dihydrophenazine in varying amounts (Scheme 53). Several variants of this procedure exist o-benzoquinone has been used in condensation with 0-phenylenediamine and yields as high as 35% have been reported, and 1,2,3,4-tetrahydrophenazine has been prepared by condensation of o-phenylenediamine with cyclohexane- 1,2-dione. 

The diester (429) has been cyclized with ammonia or primary amines to give the esters (430) (72AP2), whilst the related diester (431) has likewise been converted to (432). Similar reactions starting with TV-substituted o-phenylenediamines have been used as the basis of a synthesis of deazariboflavins (433) (77TL2551). 

If one amino group in o-phenylenediamine is converted to an amide group by formic acid, the intermediate benzimidazole is formed. This reaction, conducted with a wide range of reactants, produces resins (polybenzimidazoles) used as high-temperature adhesives for laminates in the aerospace industry. Heat insulation is made by including tiny bubbles of silica and all... 

Reaction of o-phenylenediamine and n-butyl glyoxylate gives quinoxalin-2-onc in excellent yield with 4-nitro-o-phcnylcncdiaminc (5) a mixture of 6- and 7-nitro-quinoxaIin-2-ones, (6) and (7), is obtained. ... 

Condensation of o-phenylenediamine or xV-methyl-o-phenylcne-diamine with alloxan (8) in neutral solution gives the ureides (9) and (10), respectively However, reaction of o-phenylenediamine with 1,3-dimethylalloxan (13) yields quinoxalin-3-one-2-carboxymethyl-amide (14), rather than the dimethyl ureide. Methylation of (9) in acetone in the presence of potassium carbonate gives the spiro-hydantoin (11). 

The reaction of o-diamines with w-nitroacetophenone in the presence of sodium dithionite furnishes 2-phenylquinoxalines, and reaction of o-phenylenediamine with p-N0..C,-.H4C0CH2X02 similarly gives 2- (4 -nitrophenyl) quinoxaline ... 

Cyano derivatives of (18) are prepared by reaction of o-phenylenediamine with o-CcH4(CO)2N(CH2) COC(CN)z=NCGH4NMe2-p. Hydrolysis of the latter compounds give intermediates of the type o-Cr,H4(CO)2N(CH2) COCOCN which on condensation with o-phenylenediamine yield 3-phthalimidoalkylquinoxalin-2-ones, ... 

This category is represented in the facile reaction of o-phenylenediamine (408) with 4-benzoyl-5-phenyl-2,3-dihydro-2,3-thiophenedione (409) (in toluene at 20°C for 30 min) to afford 3-(a-benzoyl-p-mercaptostyryl)-2(l//)-qumoxalinone (410) in 98% yield " also in the complicated reaction of 3-methyl-2,2,4-trinitro-2,5-dihydrothiophene 1,1-dioxide (411) with 2 equiv of ethyl 4-aminobenzoate (412) (in acetonitrile but no further details) to give ethyl 2-(p-ethoxycarbonylphenyl)-3-(l-methyl-2-nitrovinyl)-6-quinoxalinecarboxylate (413) in 51% yield.Several... 

When o-phenylenediamine (414) was heated with 5-phenyl-l,2,4-triazm-3(2/i/)-one (415) (in ethanolic hydrogen chloride under reflux for 5 h), 2-phenylquinoxa-line (417) was obtained in 34% yield the reaction is said to proceed via the tricyclic adduct (416). ° ... 

The N-bis-silylated o-phenylenediamine 1511 reacts with DMF at 120°C to give benzimidazole, in 97% yield, and dimethylamine and hexamethyldisiloxane 7, whereas reaction of benzaldehyde with 1511 gives only 29% 2-phenylbenzimida-zole 1513, because the intermediate benzimidazoline 1512 is only rather slowly dehydrogenated to 1513 [52]. Heating of N,N -bis(trimethylsilyl)ethylenediamine 1514 with DMF affords imidazoline 1515 and dimethylamine and HMDSO 7 ]52] (Scheme 9.32). The lactam 1516 cycHzes analogously with SiCU 57/triethylamine in 63% yield to give 1517 ]53]. 

The use of hydrogen peroxide in conjunction with Fe(II) (Fenton s reagent) or ozone has already been noted. It has been nsed alone to examine the products from o - and m-phenylenediamines in the context of their mntagenicity (Watanabe et al. 1989). Successive reactions produced 3,4-diaminophenazine from o-phenylenediamine, and 3,7-diaminophenazine from m-phenylenediamine. 

According to the H-NMR spectra in DMSO - de, benzodiazepine 69 exists as a 4 1 mixture of tautomers A and A. Benzodiazepin-2-one 69 is formed due to the substitution of the hydroxyl group of coiunarin 67 by one of the amino groups of o-phenylenediamine and the C - O bond cleavage in the py-rone ring upon reaction with the second amino group. 

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]... 

Similar results were obtained when o-phenylenediamine was reacted with mb. A range of low boiling compounds were separated from the reaction mixture after 10-12 hr heating at 220°C. These have been identified as diazadimethylsilaindane Vb (m.p. 76-78°C lit. (321 m.p. 75-83°C) and bis(phenylamino)dimethylsilane VIb (m.p. 46-48°C lit. (331 m.p, 45 2°C). They are probably formed by thermal decomposition of the intermediate unsymmetrical disilazane IVb". At 190-225°C/0.3 torr, a crystalline fraction with... 

VUIb is formed by dimerization of the diazasilaindane, Vb, and subsequent reaction of the cyclic dimer, Vllb, with bis(phenylamino)-dimethylsilane, VIb, as it was shown in separate experiments starting from Vb and VIb. It was subsequently found that VUIb is formed in fairly good yield whenever o-phenylenediamine is brought into reaction with difunctional silanes, such as dichlorodimethylsilane, bis(diethylamino)dimethylsilane and hexamethyl-cyclotrisilazane. 

Some negligible amounts of linear oligomers, obtained as a non-volatile, solid brown residue, were also formed on reaction of Illb with o-phenylenediamine these were almost completely soluble in toluene. No high molecular fraction was detected among the reaction products. 

The Co complexes of the o-phenylenediamine-linked dioxime Hdmg2Ph bearing a variety of monodentate ligands (halides and pseudo halides) in the axial coordination sites have been synthesized.1176 B12 model complexes [RCo(dmg2Ph)(L)]+ (R = Me, Et, Me2CH, Bz, ch L = py, H-im, or PPh3) were prepared by the oxidative addition reactions of the alkyl halide to the in situ-generated monovalent dibromo complex. 

In acid media, the complexes undergo rapid hydrolysis to yield free diamines, as shown for [Tc02(en)2] + [43]. The stability of the complexes is between that of O-coordinated and S-coordinated complexes, as shown in the reaction sequence of Tc(V) gluconate with pyridine, ethylenediamine or o-phenylenediamine to give the cationic N-coordinated species these, in turn, are able to exchange the nitrogen ligands by dithiols, such as DMSA [40]. 

Azolo[l,8]naphthyridines. The reactions of the chloronaphthyridine 229 with o-phenylenediamine at 200 °C and with sodium azide in acetic acid give the fused-ring products 230 and 231, respectively (Scheme 54) <2003IJB192>. Amino acid-substituted naphthyridines can be cyclized to the fused imidazolones 232 upon treatment with phosphorus oxychloride and under microwave irradiation (Equation 62) <2002SC857>. Acylation of 2-hydrazino-naphthyridines followed by heating gives W-acyl compounds which are cyclized intramolecularly to the [l,2,4]tri-azolo[4,3- ][l,8]naphthyridines 233 (Scheme 55) <1996IJB106>. The same compounds may also be obtained from... 

Since there appeared to be strong evidence for a nonthermal effect in this type of reaction, we repeated the reaction of o-phenylenediamine 34 (Scheme 4.13, Rj = R2 = H) with ethyl acetoacetate 35 (R = CH3) [19], which was one of the reactions reported by Soufiaoui [53] to give the diazepine only on MW heating. However, when the same reaction mixtures were heated forlO min with the same temperature profile, almost identical yields of the diazepines were obtained by MW and classical heating. Later, this was also found to be the case in the reaction of 34 with ethyl benzoylacetate 35 (R = Ph). 

However, the possibility of the participation of nonthermal effects in MW-assisted reactions in nonpolar solvents is still an open question. Loupy et al. [55] observed an increase in yield and purity of the diazepine 36, in the reaction of ethyl acetoacetate with o-phenylenediamine using monomode MW reactor with focused MW heating, when compared with conventional heating with the same temperature profile. 

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