Quinone monoimines

Oxidation H ir Colorant. Color-forming reactions are accompHshed by primary intermediates, secondary intermediates, and oxidants. Primary intermediates include the so-called para dyes, -phenylenediamine, -toluenediamine, -aminodiphenylamine, and p- am in oph en o1, which form a quinone monoimine or diimine upon oxidation. The secondary intermediates, also known as couplers or modifiers, couple with the quinone imines to produce dyes. Secondary intermediates include y -diamines, y -aminophenols, polyhydroxyphenols, and naphthols. Some of the more important oxidation dye colors are given in Figure 1. An extensive listing is available (24,28). 

L/(mol-s) (39,40). QDI is also attacked by hydroxide ion (eq. 4) to produce a quinone monoimine (QMI), itself an oxidized developer derived from /)-aminopheno1. Such compounds can further react with coupler, albeit at a slower rate than QDI, to form a dye and were cited in the seminal patent as color developers (32). However, the dyes derived from this deaminated developer have different hues from the QDI dyes, and these hues are pH-dependent as a consequence of the phenoHc group contributed by the developer. Although the deamination reaction to produce QMI is fast, the rate constant is 10 to 10 L/(mol-s) (40—42), its effect is somewhat offset by the redox reaction of the QMI with the reduced developer, present in large excess, to regenerate the desired QDI. The primary net effect of the deamination reaction is to enlarge the resulting dye cloud (43). 

The vast majority of azo dyes are azo compounds containing hydroxy or amino groups in the 2- or 4-position with respect to the azo group (e.g., 1.8). They are in equilibrium with their tautomers, the quinone hydrazones (quinone monoimine hydrazones). In spite of the fact that in most hydroxyazo dyes the equilibrium is shifted in favor of the quinone hydrazone, they are still called azo compounds. 

Dialkyl phosphite addition to quinone monoimine species, followed by elimination and rearrangement (Figure 6.7).23... 

Figure 6.7 Quinone monoimine in reaction with a dialkyl phosphite.

Quinone dyes, 9 503 Quinone ketals, anodic oxidation of hydroquinone ethers to, 21 264 Quinone methides, 2 209-211 Quinone Michael addition chemistry, 21 248-249, 250, 252 Quinone monoacetals, 21 251 Quinone monoimine (QMI), 19 246 Quinone oximes, formation of,... 

Lebold and Kerr reported the total synthesis of the eustifolines-A (172), -B (173), -C (93),-D (227), and glycomaurrol (92) starting from the readily available quinine imine 1574 and diene 1575 (899). This methodology uses the Diels-Alder reaction of a quinone monoimine 1574 and subsequent Plieninger indolization of the adduct 1576 for the synthesis of the key tetrahydrocarbazole framework. 

The photochemical addition of both aliphatic and aromatic aldehydes to o-quinones monoimines has been widely used in the preparation of oxazoles [Eq. (92)].340 An intermediate amide has been isolated in a number of cases, and can be thermally converted into the oxazole. The reaction, therefore, does not appear to be a cycloaddition. An analogous addition occurs between o-quinones and aldehydes, and the photoproducts have been shown to have an acyclic structure341 rather than the previously assigned 1,3-dioxole structure. 

As part of an examination of an oxidative coupling of methyl 6-hydroxyindole-2-carboxylate with primary amines which enabled the development of a facile preparation of 2-substituted methyl pyrrolo[2,3-e]benzoxazole-5-carboxylates, the reaction of this indole with 1,2-diaminoethane and excess Mn02 gave compound (83) in an apparent intramolecular interception of a transient intermediate o-quinone monoimine (Equation (46)) <88JOC5163>. 

Authentic N-analogs of spirobenzopyrans, the 1,2-dihydrospiro-2//-quinolines (79) (or their open forms), have never been isolated, despite many attempts during the past 35 years. In reactions with Fischer s base, 5-nitro-2-aminosalicylaldehyde gave no reaction, whereas 2-aminobenzaldehyde gave only a polymer.7 The open form of the desired compound could be considered a quinone monoimine and therefore be expected to have poor stability. 

The use of a quinone monoimine resulted in the isolation of a spirocyclic compound (equation 160), thus providing evidence for the postulated course of the reaction with the quinone227,228. The reaction is initiated by alkylation of the -position of the enaminone. 

Thiophenes can act as dienophiles in Diels-Alder reactions with electron-poor dienes such as hexachlorocyclopen-tadiene, tetrazines, or o-quinone monoimines. The masked o-benzoquinone 64 can undergo inverse electron demand cycloadditions with thiophene itself or simple derivatives such as 2-methyl-, 2-methoxy-, and 2,4-dimethylthiophene (Scheme 5) <2001TL7851>. Depending on the substitution pattern on the thiophene skeleton, different cycloadducts can be observed. The basic thiophene skeleton gives rise to a bis-adduct 65. By blocking the second double bond with a methyl or methoxy group, a 1 1 adduct 66 or 67, respectively, is obtainable in moderate yield. 

Irradiation of the two rigid derivatives (124) and (125) of 2-allylaniline, has been investigated in order to assess the potential of stereoselectivity in the intramolecular cyclization process which yields indole derivatives. Approximately 1 1 mixtures of the cis and trans diastereomeric lilolidines (126) were formed from both (124) and (125), but the latter also gave the cis and trans tetrahydropyrrolo[3,2,l-hi]indole derivatives (127). These cyclizations were carried out at several temperatures to determine whether diastereoselectivity may be entropy dependent, but the only significant effects were observed in the conversion of (125) to (126). Access to indole derivatives such as (128) can be gained by irradiation of toluene solutions of 1,4-quinone monoimines (129). ... 

Hetero-l-oxabutadiene systems that have been shown to participate as 47t components of Diels-Alder reactions include vinylnitroso compounds (31, 2-aza-l-oxabutadiene, Chapter 9, Section 3), fV-acylimines (32) as well as aromatic and aliphatic acylisocyanates (33, X = O) and isothiocyanates (33, X = S, 3-aza-l-oxabutadiene, Chapter 9, Section 3), acylnitroso compounds (34,2-aza-l, 4-dioxabutadiene, Chapter 9, Section 3), selected 4-aza-l-oxabutadienes, e.g., 35, including o-quinone monoimines (36,... 

The quinone monoimine (36) reacts with LR to yield the 1,3,2-dithiaphosphole 2-sulfide (37) (eq 31), whereas phenoxathiines are formed with phosphorus pentasulfide. ... 

Mesidine treated with K-ferricyanide in methanol-water containing KOH azo compd. Y 91-95%. Also formation of quinone monoimines s. S. L. Goldstein and E. McNelis, J. Org. Chem. 38, 183 (1973). 

Attempts to form surface-confined poly(aniline) have previously been made using 4-aminothiophenol on Au. After oxidation of the monolayer and successive potential scans, this monolayer was found to produce a surface-confined redox active film. Recently, elucidation of the coupling and degradation pathways of this molecule on Au was reported. Radical-radical coupling was found to occur between adjacent aminothiophenol molecules yielding an electrode surface modified with 4 -mercapto-4-aminodiphenylamine. Upon potential scanning of the surface-confined aniline dimer, an electrochemical-chemical-electrochemical (ECE) reaction was found to occur. Oxidation of the quinonediimine resulted in hydrolysis of the dimer to yield a quinone monoimine species. Further oxidation of this molecule then produced the initial 4-aminothiophenol molecule as well as benzoquinone in solution. 

Quinone monoimines and N -cyanoazoformamidines from diazocyanides and phenols N,N-Cleavage of azo groups... 

Lithium aluminum hydride Aminophenols from quinone monoimines... 

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