- A general and scalable synthesis of polysubstituted indoles
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A consecutive 2-step synthesis of N-unprotected polysubstituted indoles bearing an electron-withdrawing group at the C-3 position from readily available nitroarenes is reported. The protocol is based on the [3,3]-sigmatropic rearrangement of N-oxyenamines generated by the DABCO-catalyzed reaction of N-arylhydroxylamines and conjugated terminal alkynes, and delivers indoles endowed with a wide array of substitution patterns and topologies.
- Diana-Rivero, Raquel,García-Tellado, Fernando,Tejedor, David
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- A New Method for the Synthesis of 3-Substituted Indoles
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Starting from readily accessible nitrones and electron-deficient acetylenes, a highly efficient and versatile synthetic protocol for 3-substituted indoles has been developed.
- Natarajan, Rakesh,Rappai, John P.,Unnikrishnan, Peruparampil A.,Radhamani, Sandhya,Prathapan, Sreedharan
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supporting information
p. 2467 - 2471
(2015/10/19)
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- Aryliminopropadienone-C-Amidoketenimine-Amidinoketene-2-Aminoquinolone Cascades and the Ynamine-Isocyanate Reaction
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Imidoylketenes 11 and oxoketenimines 12 are generated by flash vacuum thermolysis of Meldrum's acid derivatives 9, pyrrolediones 17 and 18, and triazole 19 and are observed by IR spectroscopy. Ketenimine-3-carboxylic acid esters 12a are isolable at room temperature. Ketenes 11 and ketenimines 12 undergo rapid interconversion in the gas phase, and the ketenes cyclize to 4-quinolones 13. When using an amine leaving group in Meldrum's acid derivatives 9c, the major reaction products are aryliminopropadienones, ArN=C=C=C=O (15). The latter react with 1 equiv of nucleophile to produce ketenimines 12 and with 2 equiv to afford malonic acid imide derivatives 16. N-Arylketenimine-C-carboxamides 12c cyclize to quinolones 13c via the transient amidinoketenes 11c at temperatures of 25-40 °C. This implies rapid interconversion of ketenes and ketenimines by a 1,3-shift of the dimethylamino group, even at room temperature. This interconversion explains previously poorly understood outcomes of the ynamine-isocyanate reaction. The solvent dependence of the tautomerism of 4-quinolones/4-quinolinols is discussed. Rotational barriers of NMe2 groups in amidoketenimines 12c and malonioc amides and amidines 16 (24) are reported.
- Wentrup, Curt,Rao, V. V. Ramana,Frank, Wilhelm,Fulloon, Belinda E.,Moloney, Daniel W. J.,Mosandl, Thomas
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p. 3608 - 3619
(2007/10/03)
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