Acridine quinones

SCHEME 9.17 DNA cross-linking by a quinone methide-acridine conjugate. 

The quinone methide (11) derived from flavan by a retro-Diels-Alder reaction gives only a 4% yield of acridine when heated with aniline. However, the other products include the diphenylmethane (12) and the Mannich base (13) both of which yield the tricyclic compound upon pyrolysis (J.L. Asherson. 0. Bilgic and D.W. Young, J. chem. Soc. Perkin I, 1980, 522). 

The addition of the enolate of dimedone to the aminoquinone (112) generated from the corresponding azidonaphthoquinone also leads to a benzo[b]acridine-6, 11-quinone (A.J. Hamdan and H.W. Moore, J. org. Chem., 1985, 50, 3427). 

Bilgic and Young have reported the formation of the benzo[ ]pyrrolo[2,3-h]acridine 294 in a reaction between 1-(Y, Y-dimethylaminomethyl)naphth-2-ol 292 and 5-aminoindole. A quinone methide 293 is believed to be involved as an intermediate (Scheme 52). The reaction of the naphthol 292 with 5-aminoindazole gave the angular pyrazoloacridine 295 [80JCS(P1) 1233]. 

Air oxygen can also play the role of oxidant in the amination reactions. It is well known that 1,4-benzoquinone reacts with aliphatic amines in the presence of copper acetate to give 2,5-bis(dialkylamino)-l,4-benzoquinones in good yields [64]. The reaction mechanism involves nucleophilic 1,4-addition followed by oxidation of intermediate aminohydroquinones with air oxygen. The reactions of this type, which are also inherent to ort/io-quinones, have been reviewed earlier [65, 66]. It is interesting that amination is also possible in case of some heterocyclic phenols, which are first converted in situ into the corresponding ort/io-quinones. This approach has successfully been exploited to aminate ort/io-quinones generated from quinolines, indoles, acridines, isoquinolines, quinoxalines, benzofurans, and benzothiazoles (Scheme 15) (for review, see [65, 66]). 

Dibenzoparathiazine. See Phenothiazine Dibenzopyran, tricyclic. See Xanthene Dibenzo (a,b) pyrene-7,14-dione 2,3,7,8-Dibenzopyrene-1,6-quinone. See Vat yellow 4 2,3,5,6-Dibenzopyridine Dibenzo (b,c) pyridine Dibenzo (b,e) pyridine. See Acridine Dibenzopyrrole. SeeCarbazole Dibenzosuberan-5-one. See Dibenzosuberone Dibenzosuberone... 

On the other hand, when o -adducts of arylacetonitrile carbanions to para-substituted nitroarenes are converted into substituted nitrosoarenes in aprotic media via silylation in the presence of trialkylamines, the produced o-nitrosoaryl acetonitriles can undergo further hetero-cyclization on alternative pathway to produce substituted acridines [28]. Reactions of arylacetonitriles with nitroarenes unsubstituted in the para position under identical protic conditions result in the formation of p-nitrosoaryl arylacetonitriles that can be isolated in the tautomeric form of p-arylcyanomethylene quinone oximes (Scheme 11.13) [27b]. 

Theoretical studies have been carried out on the conrotatory and disrotatory reaction pathways of hexa-l,3,5-triene to cyclohexadiene, and the effect of solvent and salt effects on the rates of the electrocyclic ring closure of (IZ, 3Z, 5 )-l,2,6-triphenylhexa-l,3,5-triene has been determined. An ab initio study of the electro-cyclization of (Z)-hexa-l,3,5-triene and its hetero-substituted analogues has been undertaken.The involvement of a lone pair on the nitrogen or oxygen atom appears to facilitate the interaction between the terminal atoms that bond to each other to close the ring. It has been reported that the intramoiecular aza-Diels-Alder reaction of an a./S-unsaturated hydrazones to a quinone, as in (197), is followed by an unprecedented rearrangement in which the aminoaryi moiety formally undergoes a 1,2-shift to yield benzo- or pyrido-[fc]acridine-6,11-dienes (198). 

A wide assortment of electron transfer photosensitizers for diaryiiodonium salts have been described in the journal and patent literature. Among these are polynuclear aromatic hydrocarbons with three or more rings such as anthracene, alkoxyanthracenes, pyrene, and perylene heterocyclic compounds of low basicity such as carbazoles " and phenothiazines aromatic ketones such as benzophenone, Michler s ketone, and thioxanthone and substituted thiox-anthones coumarins phenanthrene-9,10-quinone Mannich bases and (dimethylamino)benzylidyne compounds. In addition, the use of dyes such as eosine, acridine orange, acridine red, and benzoflavin has been employed to provide photosensitization in the visible region of the spectrum. 

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