Carbazole synthesis via an in situ trapping strategy with indolyl enol ethers

Abstract

Indolyl enol ethers, generated from the alkoxy(indolyl)carbenium tetrafluoroborates 1 by treatment with sodium hydride, can be trapped with dimethyl acetylenedicarboxylate or N‐phenylmaleimide to furnish the selectively functionalized carbazoles 3,4,5,9,10, and 13. In addition, the biaryl derivatives 6 and 11 are produced by a ring‐opening reaction of the primarily formed Diels‐Alder adduct. In the case of the biaryl derivative 6, an X‐ray crystal structure analysis yields valuable information on constitutions and configurations in the biaryl series. The phenomenon of atropisomerism is discussed for this compound.

Synthesis of indoles and carbazoles from a lignin model compound α-hydroxyacetophenone

“…Like pyrrole, indole can also act as a 1,2-bisnucleophile to construct carbazole scaffolds via [2 + 4], [2 + 2′ + 2′] and [2 + 2′ + 2′′] annulation reactions. 25–27 Therefore, we tried to use glycerol/Sc(OTf) 3 for establishing a three component reaction of α-hydroxyacetophenone, 1-methylindole and a 1,3-dicarbonyl compound, and the results are given in Scheme 4. Although the result obtained via the use of indole derivatives as the substrates to synthesize products was not as good as pyrrole, the synthetic efficiency achieved is acceptable.…”

[4 + 2]Cycloaddition of indole derivatives with bismaleimides: a route to new biscarbazoles

“…18 The quality and precision of the application of the AM1 method to anellated carbazole heterocycles has been documented by us. 19 …”

Pyrrolo-Annellated Carbazoles as Potential Antitumour-Active Compounds: Dimethyl 4-Methoxy-9-methyl-9H-carbazole-1,2-dicarboxylate and 5-Hydroxy-2-phenyl-10-methyl-1,2,3,10-tetrahydropyrrolo[3,4-a]carbazole-1,3-dione Methanol Solvate

“…Compound (1) is readily available from a Diels-Alder reaction of in situ generated 1-(N-methylindolyl)-l-methoxyethene and dimethyl acetylene dicarboxylate followed by spontaneous dehydrogenation (Pindur, Rogge, Rehn, Massa & Peschel, 1994). The [a]-annellated carbazole of compound (2) is readily available from in situ generated 1-(N-trimethylsilylindol-3-yl)-l-(trimethylsilyloxy)ethene and N-phenylmaleimide; the [4+2] cycloadduct primarily formed is dehydrogenated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (Rogge, Fischer, Schollmeyer & Pindur, 1996).…”