Aminophthalate

In fact, the 4- or 3-aminophthalic anhydride (4-APA and 3-APA) gives only intractable oligomers as pointed out later.154 Interesting are the attempts of vapor-phase deposition of 4-APA, 3-APA, and 4-amino naphtlialic anhydride (4-ANA). The sublimation of 3-APA gives only a low yield of polyimide. With both 4-APA and 4-AN A no sublimation took place and oligomeric products were formed before melting.154... 

It has been established 106> that 3-aminophthalate is the emitting species in luminol chemiluminescence and that in all known cases of other cyclic hydrazides the corresponding dicarboxylate is the emitter (e.g. 97,107)). 

The maximum of luminol chemiluminescence emission is at 425 nm in aqueous and at 480 nm in DMSO-containing solvent. It was suggested that different anions of 3-aminophthalate were responsible for this phenomenon, namely 51 (in water) and 52 (in aprotic solvents). 

D. S. Bersis and J. Nikokavouras 108> came to the conclusion, on the basis of their chromatographic investigations of luminol preparations, that these two emission maxima of luminol chemiluminescence were actually due to impurities in luminol, not to different states of 3-aminophthalate. Recent investigations of 3-aminophthalate in solution 109)... 

However, the formation of these products does not appear to play a critical role in the decision as to whether the 425 nm and 480 nm maxima are due to different states of the same molecule or to different compounds. It was reported that special care was taken to ensure the purity of luminol and of 3-aminophthalate 109>. In commercially available 3-amino-phthalic acid a yellowish impurity exhibiting brilliant green fluorescence was detected 109> this substance also formed in neutral solutions of pure 3-amino phthalic acid and crystallized from these solutions in yellow crystals. The structure of this substance was determined to be 53 its absorption spectrum has a maximum at 388 nm the fluorescence maximum is at 475 nm, with a fluorescence quantum yield of about 0.75 in DMF i 9). 

Albrecht [10] was the first to report the CL of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione), in 1928. The chemiluminescent reaction involves the oxidation of luminol (usually by H202) and often occurs in the presence of a catalyst (or co-oxidant) such as Fc(CN)6 3, Cu(II), or Co(II)) (Fig. 2). The light emission, which is blue in water and yellow-green in DMSO, is identical with the fluorescence of the 3-aminophthalate oxidation product [11],... 

Fig. 24 (a) Chemiluminescence reaction of luminol (63) to 3-aminophthalic acid (64). (b) Oxidation of diphenyloxalate (65) to produce the high-energy dioxetandione as a sensitizer for an organic dye fluorophore... 

Lugol solution chem A solution of 5 grams of iodine and 10 grams of potassium iodide per 100 milliliters of water used in medicine. Iu,g6l so lir-shon luminol orgchem CgffyNjOj Awhite, water-soluble, crystalline compound that melts at 320°C used in an alkaline solution for analytical testing in chemistry. Also known as 3-aminophthalic hydrazide. lu mo.nol )... 

It is generally agreed that the CL obtained with Inminol (124) is based on the series of transformations shown in Scheme 3, where the analyte (oxidant) as such or in combination with a catalyst prodnces a free radical (125), which in him captnres a superoxide anion to yield an endoperoxide (126), which on elimination of N2 prodnces an excited intermediate (127), which finally settles down to the 3-aminophthalate ion (128) on emission of a photon. A hnear correlation may be established between the intensity of the CL emission and the concentration of the analyte. ... 

The chemiluminescence emission resulting from the oxidation of luminol (5-amino-2,3-dihydro-l,4-phthalazinedione) has been extensively studied since its discovery by Albrecht in 1928. Although luminol oxidation is one of the most commonly applied chemiluminescent reactions, to date no definitive mechanism is known . Efficient chemiluminescence emission is only observed when luminol (25) is oxidized under alkaline conditions. Depending on the medium, co-oxidants are required in addition to molecular oxygen for the observation of light emission, but under any condition, 3-aminophthalate (3-AP) and molecular nitrogen are the main reaction products (equation 10). 

The emitting species was found to be the singlet-excited state of 3-aminophthlate ion in both protic and aprotic solvents. This identification was made based on the equivalence of the chemiluminescence spectrum of luminol and the fluorescence spectrum of 3-AP ion . In different reaction media, slightly different maximum chemiluminescence wavelengths are observed (Table 2). The spectral shift observed when the system changes from aqueous media to DMSO or other aprotic solvents can be ascribed to a quinoidal form of 3-aminophthalate (26) formed in aprotic solvents (Scheme 15). ... 

TABLE 2. Chemiluminescence maxima of luminol and fluorescence maxima of 3-aminophthalate (F13 ap) ... 

In aprotic media, only molecular oxygen and a strong base are needed to produce chemiluminescence from luminol. In such media, an important intermediate in the reaction is the dianion of luminol, which can be oxidized by oxygen, resulting in the formation of the diazaquinone 27 and deprotonated hydrogen peroxide. The subsequent nucleophilic attack by hydrogen peroxide dianion to one of the diazaquinone carbonyls gives rise to the formation of a metastable peroxidic intermediate that, by several steps, results in chemiexcited 3-aminophthalate (Scheme 16)123,174, iso ... 

Steinfatt proposed an alternative mechanism for the formation of excited aminophth-alate, based on the concept of dioxirane-carbene mediated chemiexcitation, which is also attributed to other chemiluminescent systems ° °. After the attack of hydrogen peroxide on the diazaquinone 27 carbonyl carbon, a perhydrolysis step is postulated to result in the intramolecular dioxirane-carbene system (32) in the excited state ° ° . This species presumably rearranges to 3-aminophthalate dianion while still in the singlet-excited state (Scheme 23). Although this is a very interesting mechanistic proposal, it is based on experimental evidence obtained with indirect phthaloyl peroxide chemiluminescence and no further evidence corroborates this proposal. 

A CIEEL approach can also be used to explain chemiexcitation in luminol chemilumi-nescence . Two possibilities arise (i) an electron transfer from the amino group to the peroxidic moiety in the antiaromatic peroxide 33, resulting in bond cleavage followed by intramolecular back-electron transfer and formation of excited 3-aminophthalate (Scheme 24) (ii) the equilibrium between the peroxycarboxylic aldehyde 34, formed after elimination of nitrogen, and the cyclic peroxy semiacetal 35 is shifted in the direction of 35, as the result of an electron transfer from the amino group to the cyclic peroxide moiety, followed by 0—0 bond cleavage . Back-electron transfer would result in chemiexcitation (Scheme 25). 

Ai -Aminooxymethylcarbonylhydrazino-D-biotin, DNA oxidative damage, 736, 634 3-Aminophthalate, luminol oxidation, 643, 644, 1239-41, 1244-6 7-Amino-4-trifluoromethylcoumarin, hydrogen peroxide determination, 649 Ammonium ion complex, mass spectrometry, 703, 704... 

The reaction of maleic anhydride with trimethylsilyl azide was reported to provide l,3-oxazine-2,6-dione in good yield. Control of the temperature proved essential in order to avoid a violent, exothermic reaction this could readily be accomplished by running the reaction in methylene chloride at 0°C <19950PP651>. Similar transformations of 3-substituted phthalic anhydrides 546 resulted in formation of 8- 547 or 5-substituted 548 isatoic anhydrides (Equation 66). The ratio of the regioisomeric products was strongly influenced by the substituent X while nitro and acetylamino derivatives 546 (X = NO2, NHAc) gave exclusively the 8-substituted isomers, only the 5-substituted product was formed from 3-aminophthalic anhydride 546 (X = NH2) <1998JOC6797>. 

The [4 + 2] cycloaddition reaction of 2- or 2,5-substituted iV-methoxycarbonylpyrroles with dimethyl acetylenedicarboxylate is accelerated tremendously by aluminum chloride (70CJC1472). The Diels-Alder cycloaddition is in fact complete in some cases within 30 min at 0 °C if five molar equivalents of A1C13 are utilized. On warming the reaction mixture to 40 °C, the 7-azabicyclo adduct (199) formed initially undergoes rearrangement to an Af-methoxycarbonyl-3-aminophthalate (200 Scheme 42). The overall scheme constitutes a valuable method for the construction of polysubstituted anilines. 

Several other chromophores have been used in the development of sensors based upon ECL. For example, the luminol reaction is a conventional chemi-luminence reaction that has been studied in detail and it is believed that the mechanism of the ECL reaction is similar, if not identical, to that of the chemiluminescence. As shown in Fig. 2, the luminol ion undergoes a one-electron oxidation to yield a diazaquinone, which then reacts with peroxide or superoxide ( OOH) to give the excited 3-aminophthalate which has an emission maximum of 425 nm. This reaction is particularly versatile and has been utilized in a variety of ECL assays, many of which have been previously summarized by Knight [1], The luminol ECL reaction can be used for the determination of any species labeled with luminol derivatives, hydrogen peroxide, and other peroxides or enzymatic reactions that produce peroxides. A couple of examples are described later. 

Fluorenonecarboxylic ac(ds are accessible from the products formed by coupling diazotized esters of methyl 3-aminophthalic acids with benzene and benzene derivatives. From diazotized methyl 3-aminophthalate and benzene, methyl 3-phenylphthalate (IX) is obtained in 35% yield. 

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