1,4-Benzoquinone monoimine

Boulos, L.S. and Arsanious, M.H.N., The novel behavior of dialkyl phosphites toward 1,4-benzoquinone monoimines, Tetrahedron, 49, 4711, 1993. 

Benzoquinone monoimine, 2260 t Bicyclo[2.2.1]hepta-2,5-diene, 2789 t 1,2-Butadiene, 1479... 

Cyclohexadiene-l,4-dione, see 1,4-Benzoquinone, 2207 2,5-Cyclohexadienone-4-imine, see 1,4-Benzoquinone monoimine, 2253 f Cyclohexane, 2451... 

This process is very important in the HALS stabilization mechanism. It should, however, be considered only as a minority pathway in diarylamines just because of the lower stability of the corresponding diarylnitroxides. This results in the participation of the latter in side reactions leading to antioxidant ineffective species, e.g. benzoquinone (BQ) and nitrobenzene ( 7 ). Transformation of diarylnitroxide into a mixture of diarylamine and N-aryl-1,4-benzoquinone monoimine-N-oxide (4. 8) seems therefore to be a more probable pathway regenerating partly amine antioxidant than the hydroxylamine/nitroxide cyclical process (Scheme 2). 

The Lewis acid promoted reactions of styrene with 7V-phenylsulfonyl-l,4-benzoquinone monoimine to the 2-aryIbenzofuranoid ring system have been reported previously. This offers a new route to henzofinanoid neoUgnans (( )-hcarin B, eupomatenoid-1, eupomatenoid-12) (Scheme 25, <96TL6969>). 

Hydroxyindoles may be accessed using the Nenitzescu reaction, as illustrated by preparation of the indole 381 from the enamine 382 and 1,4-benzoquinone (Equation 107) <1996JOC9055>. Additional applications of this strategy encompass syntheses of 1 -alkyl-5 -hydroxynaltrindole derivatives <2005JME635>, and lO-hydroxy-5,6-dihydroindolo[2,l- ]isoquinolines <2001JOC4457>. An alternative approach to 5-hydroxyindole derivatives involves Lewis acid-mediated reactions of benzoquinone monoimines with enol ethers <1997TL6135>. 

A general approach to 2-aryl-7-alkoxy-benzofuranoid neolignans is based on a Lewis acid-promoted reaction of styrenes with A -phenylsulfonyl-l,4-benzoquinone monoimines. Regioselective formation of the 2-arylbenzofuranoid ring system is followed by conversion of the aromatic A -phenylsulfonyl moiety into a propenyl substituent (Equation 147) <1996TL6969>. 

Elastomers BHT, Cyanox 2246, Cyanox 425, Permanax WSP, Naugawhite, Wingstay T, Naugard SP, Vulkanox CS Soxhlet extraction with acetone, evaporative concentration Merck 11845 silica gel Benzene Sprayed with 2.34% sodium tetraborate, 0.33% sodium hydroxide, and 0.1% methanolic solution of A-chlorodichloro-2,6-p-benzoquinone monoimine Sample size 20 pL [38]... 

Reaction of mesomeric C-radicals 42b and 42c with ROO is a competitive process to the nitroxide formation and accounts for coloured benzoquinone monoimines (BQMI), e.g. 1 -phenyl-1,4-benzoquinone-4-imine (57, R = H) or 1,2-benzoquinone imine 58, (R = ter/-octyl or an aralkyl) [5]. QI 58 transforms further into 3,7-di-te/7-octyl-1 //-phenoxazone-1 (59) or 2-(4 -tert-... 

Data on sulphonamides derived from imines (e.g. AT-arenesulphonyl benzoquinone monoimines)... 

Sprayed with 2.34% sodium tetraborate, 0.33% sodium hydroxide, and 0.1% methanolic solution of /V-chlorodichloro-2,6-p-benzoquinone monoimine... 

Upon dissolution of the catalyst precursor in MeOH one of the axial AsPhs ligands dissociates, generating the active pentacoordinate [Co(Hdmg)j(AsPh3)J catalyst, denoted by Co . The key intermediate is the superoxocobaloxime derivative Co (02), which abstracts an H-atom from the ap substrate via an H-bonded species X. The aminophenoxyl radical (ap ) produced is further oxidized to o-benzoquinone monoimine (bqmi), which is an intermediate on the path to apx formation. EPR studies provide evidence for formation of the ap free radical as intermediate. ... 

Nair and coworkers reported that the choice of Lewis acid is crucial in the addition of allyltriisopropylsilane onto p-quinoneimines (37) (Equation 23) and p-benzoquinone monoimine (38) (Equation 24) [28]. When BF3 OEt2 is used for this reaction, the products obtained are indane derivatives. 

Benzoquinone-1,4 monoimine [called Benzochinon -(1.4)-mDnDimid p-Chinon-monoimid Dr p-Chinon-imid in Ger], HN CgH4 0 mw 107.11, N 13.08% ... 

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. 

The rates of formation of some phenazines by cyclization of di- and monoimines of JV-(2-aminophenyl)-l,4-benzoquinone have been determined spectrophotometrically. The reaction of 2-aminoindamines (quinoneimines) is a similar example (see Hotiben-Weyl, Vol. 7/3 b, p 330). The oxidation of benzene-1,2,4-lriamine (16) takes place through a series of intermediates, c.g. initial oxidation of 2-amino-l, 4-quinonediiminc (17) is followed by its condensation with beiizene-1,2,4-triamine (16) which leads to the formation of the indamine derivative 18 which, on further oxidation, undergoes cyclization to the amino-substituted phenazine. Different isomers of phenazinetriamines 19 can thus be formed. 

Diaryl ketimines are more stable than alkyl aryl ketimines which in turn are more stable than the purely aliphatic ketimines since conjugation increases the thermodynamic stability of the azomethine linkage Benzophenone imine (3), with a melting point of 48°c is quite stable . Although the monoimine of j>-benzoquinone is very unstable, the diimine (4) is sufficiently stable to be studied spectroscopically . V... 

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. 

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