Benzo indol

Acyloxynaphthoquinones and secondary alkylaminocrotonates react to give 4-hydroxy benzo(gf)indoles and benzo(/)indole-4,9-dione in a low yield138 (equation 91). 

Indoles and azaindoles undergo smooth oxidation with 2-iodoxybenzoic acid in the presence of indium(lll) chloride (aqueous media, 80 °C) to afford the corresponding isatins in excellent yields <2007S0693>. A peculiar rearrangement to 3//-benzo[< ]indole during the NiS-catalyzed dehydrogenation of 4,5-dihydro-l//-benzo g]indole (350 °C) was reported <2007MC296>. 

The 5//-pyrido[4,3-f ]benzo[/]indole ring system (e.g., 192) represents another type of isoellipticine, and its synthesis has been explored by Bisagni and co-workers (95) (Scheme 33). Azaindole 188 was elaborated by means of conventional lithiation methodology to alcohol 189. A sequence of dehydration, hydrogenation, and chlorination gave 190. Either Vilsmeier-Haack conversion to aldehyde 191 and polyphosphoric acid (PPA) cyclization to the desired ring system 192 or direct cyclization to 192 completed the synthesis. The side chain amines were introduced by heating the components neat to provide 193-195. The methoxyl derivatives 196 and 197 were also synthesized (95). 

Scheme 33. Synthesis of the 5//-pyrido(4,3-/>]benzo[/]indole ring system (192) by Bisagni and co-workers (95).

Ojty.2.6-dioxo-l-acetyl-2.6.dlhydro-4.S.benzo-indol-oarboiufture-(3)- thyU eater 82, 379. 

Oxy>6 phenyl-a-8tilbazol 21,102. 2 OxO 8 methyl.l-pheiwl-2.8- hydro-6.7 benzO indol 21 II278. 10 Athyl-2.3 benzo acridon 21, 307. 3,0-Di8t l[Pg.1287]

Inchlor.4-methyI-thionaphthen-(2)]. [4.5-benzo-indol-(2)]-indigo 27 II 324. CtilluCLNOg l.Cblor-2-[2-chlor-benzainino]-anthrachinon 14 1 456. 

C uCIN gS [9>Aoetunmo-l-thia-peri naphthlnden-(2)]-[7-ohIor>5.6 benzo. indol.(2) >ind%o 27 0 487. 

Ace dehvat des 9-Oxy-2-ozo-8-methyl-l phenyl 2.3.4.5.8.9-hez(diydro.6.7>benzo -Indols 21 II426. 

Reaction with 2-Aminoquinones. Acyl and carbox3miethyl radicals generated using Mn(OAc)3 react with 2-aminoquinones in a fashion similar to that of their naphthoquinone counterparts. In case of 2-arylainino-l,4-benzoquinones, sequential radical addition/cycUzation occurs to afford the corresponding acridine derivatives (eq 34). The yield is lowered in the presence of an electron-withdrawing group on the aniline. Benzo[/]-indole-4,9-diones and their derivatives can be obtained exclusively with... 

Hstzpbin (1R,2R)-1 -(3 -(l//-tetrazol-5-yl)phenyl)-2-(pyridin-4-yl)-2,3-dihydro-l//-benzo[ ]indole... 

---