Benzo carbazole diones

Prior to the discovery of the aryl-Heck reaction (Chapter 72), the direct Pd-promoted oxidative cyclization of diaryl amines to carbazoles was well known. In 1975 Akennark reported this reaction (Scheme 1, eqnation 1) [1], In addition, A -phenylanthranUic acid gave carbazole-l-carboxylic acid (60%). Miller and Moock used Pd(OAc)j to cyclize 6-anilino-5,8-dimethylisoquinoIine to eUipticine in low yield [2]. The second advance in this chemistry was reported independently by Bittner [3] and Furukawa [4], who described the Pd-mediated (stoichiometric) oxidative conversion of 2-anilino-l,4-benzoquinones and 2-anilino-l,4-naphthoquinones to the corresponding carbazole-l,4-diones and benzo[ ]carbazole-l,6-diones (equations 2, 3). Furukawa s studies included syntheses of several carbazolequinone alkaloids. In 1995 Akermark and colleagues developed catalytic versions (i.e., using tert-butyl hydrogen peroxide [TBHP] or oxygen) of this cyclization (equation 3) [5,6], which elevated the importance of this palladium oxidative cyclization, mainly because of the expense of Pd(OAc)2. Somewhat earlier, Knbiker used cupric acetate as a reoxidant in a synthesis of carbazole-l,4-quinones [7]. 

Scheme 15.16 Palladium(ll)-catalyzed oxidative cyclization to 4-methoxy-2-methyl-5H-benzo[fo]carbazole-6,l 1-dione.

Recovered starting material (N-[2-methoxy-4-methylphenyl]-2-amino-l,4-naphthoquinone). Isolated yield of 4-methoxy-2-methyl-5H-benzo[l)]carbazole-6,ll-dione. 

Palladium(II)-promoted oxidative cyclization was also applied to benzo[b]carbazole-6,ll-diones. <94T10893>... 

Dihydro-llH-benzo[a]carbazole oxidized with periodate according to Synth. Meth. 21, 182 ll,12-dihydro-5H-dibenz[b,g]azonine-6,13-dione (Y 85%) dissolved in 2 N NaOH, allowed to stand at room temp, overnight, and the resulting crude 4-quinolone refluxed 5 hrs. with PCI5 in POCI3 10-chloro-llH-indeno-[l,2-b]quinoline (Y 77%) hydrogenated 2 hrs. with 10%-Pd-on-carbon in methanol llH-indeno[l,2-b]quinoline (Y 91%). F. e. s. J. A. Beisler, J. Med. Chem. 14, 1116 (1971). 

IH-benzo [a]carbazoles, 5,6-dihydro- 28, 903 Indole-4,7-diones 24,528 suppl. 28... 

In addition to carbazoles, pyrrole ring-containing PAHs such as 7/f-indolo[2,3-clquinoline 9,1 l//-indolo[3,2-c]isoquinoline 11, 9/7-pyrrolo[2,3- 4,5-c ]dipyridine 13a, 9/7-pyrido[2,3- ]indole 13b, benzo[a]pyrrolo[3,4-c]carbazole-l,3-(2//,8//)-dione 15, and 6//-indolo[3,2-fe]benzo[fe]thiophene 17 were accessible by intramolecular direct arylation strategy (Scheme 22.4) [10]. The cyclization of 3-(2-bromophenylamino)quinoline 8 and 4-(2-bromophenylamino)isoquinoline 10 was catalyzed by Pd(PPh3)2Cl2 in the presence of NaOAc in DMA and reached to... 

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