- A convenient access to 1,3-disubstituted furo[3,4-b]indoles by acid ion-exchange resin-catalyzed furan formation
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Efficient synthesis of furo[3,4-b]indoles starting from the corresponding indole is reported. The first route involves derivatization, protection, and deprotection steps, which stretch the syntheses. The second method provides a shorter and more efficient strategy to accessing the furoindole. The innovation starts with alkylation at C-2 of the indole presenting at the C-3 position a ketone-acetal, followed by the cycloaromatization catalyzed by polymeric ion-exchange resins. The second route represents a significant improvement over other methods previously described.
- Basset, Joan,Romero, Manel,Serra, Tha?s,Pujol, M. Dolors
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p. 356 - 362
(2012/01/06)
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- Synthesis and Diels-Alder Reactions of 1,3-Dimethyl-4-(phenylsulfonyl)-4H-furoindole. A new Annulation Strategy for the Construction of Ellipticine and Isoellipticine
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The novel fused heterocycle 1,3-dimethyl-4-(phenylsulfonyl)-4H-furoindole (4) is synthesized from 3-ethylindole (6) in six steps (46percent yield) or from indole-3-carboxaldehyde (12) in four steps (21percent yield).Furoindole 4 undergoes Diels-Alder reactions with dimethyl acetylenedicarboxylate, N-phenylmaleimide, benzyne, and 3,4-pyridyne (5) to give the expected adducts 17, 18a,b, 19, and 23a,b, respectively.Deoxygenation and desulfonylation of 19 and 23a,b, respectively, give benzocarbazole 22 and a readily separable mixture of the pyridocarbazole alkaloids ellipticine (1a) and isoellipticine (2a).
- Gribble, Gordon W.,Saulnier, Mark G.,Sibi, Mukund P.,Obaza-Nutaitis, Judy A.
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p. 4518 - 4523
(2007/10/02)
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- 4-(PHENYLSULFONYL)-4H-FUROINDOLE - A STABLE SYNTHETIC ANALOGUE OF INDOLE-2,3-QUINODIMETHANE
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The N-phenylsulfonyl derivate (2) of the previously unknown fused heterocycle 4H-furo indole is synthesized from indole-3-carboxaldehyde (3) in 28percent yield and undergoes a Diels-Alder reaction with benzyne to give 5H-benzocarbazole (11) in 33percent yield after deoxygenation and deprotection.
- Saulnier, Mark G.,Gribble, Gordon W.
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p. 5435 - 5438
(2007/10/02)
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