19283-51-3Relevant academic research and scientific papers
Unambiguous characterisation of dienylimines as intermediates in Fischer indolisation of o-substituted N-trifluoroacetyl enehydrazines
Miyata, Okiko,Kimura, Yasuo,Naito, Takeaki
, p. 2429 - 2430 (1999)
Thermal cyclisation of o-substituted N-trifluoroacetyl enehydrazines was systematically investigated and found to proceed via dienylimine intermediates, which were unambiguously characterised by X-ray and spectral analysis.
Direct Synthesis of Indoles from Azoarenes and Ketones with Bis(neopentylglycolato)diboron Using 4,4′-Bipyridyl as an Organocatalyst
Misal Castro, Luis C.,Sultan, Ibrahim,Nishi, Kohei,Tsurugi, Hayato,Mashima, Kazushi
, p. 3287 - 3299 (2021/03/01)
Multifunctionalized indole derivatives were prepared by reducing azoarenes in the presence of ketones and bis(neopentylglycolato)diboron (B2nep2) with a catalytic amount of 4,4′-bipyridyl under neutral reaction conditions, where 4,4′-bipyridyl acted as an organocatalyst to activate the B-B bond of B2nep2 and form N,N′-diboryl-1,2-diarylhydrazines as key intermediates. Further reaction of N,N′-diboryl-1,2-diarylhydrazines with ketones afforded N-vinyl-1,2-diarylhydrazines, which rearranged to the corresponding indoles via the Fischer indole mechanism. This organocatalytic system was applied to diverse alkyl cyclic ketones, dialkyl, and alkyl/aryl ketones, including heteroatoms. Methyl alkyl ketones gave the corresponding 2-methyl-3-substituted indoles in a regioselective manner. This protocol allowed us to expand the preparation of indoles having high compatibility with not only electron-donating and electron-withdrawing groups but also N- and O-protecting functional groups.
An Electrophilic Bromine Redox Catalysis for the Synthesis of Indole Alkaloid Building Blocks by Selective Aliphatic C?H Amination
Bergès, Julien,García, Belén,Mu?iz, Kilian
supporting information, p. 15891 - 15895 (2018/11/23)
A new homogeneous bromine(?I/I) redox catalysis is described, which is based on monomeric bromine(I) compounds containing transferable phthalimidato groups. These catalysts enable intermolecular C?H amination reactions at previously unaccessible aliphatic positions and thus enlarge the synthetic potential of direct C?N bond formation, including its application in the synthesis of alkaloid building blocks. This aspect is demonstrated by a new synthetic approach to aspidospermidine. In addition to the development of the catalyst system, the structures of the involved bromine(I) key catalysts were fully elucidated, including by X-ray analyses.
Ruthenium-catalyzed synthesis of indoles from anilines and epoxides
Pena-Lopez, Miguel,Neumann, Helfried,Beller, Matthias
supporting information, p. 1818 - 1824 (2014/03/21)
A general synthetic route to indoles from readily available anilines and epoxides by using ruthenium catalysis is described. This straightforward transformation allows a variety of indoles to be obtained in good yields by using [Ru3(CO)12]/1,1-bis(diphenylphosphino)ferrocene as the catalytic system. Water and hydrogen are formed as the only stoichiometric by-products, making this process highly atom efficient.
Highly enantioselective hydrogenation of N-unprotected indoles using (S)-C10-BridgePHOS as the chiral ligand
Li, Chao,Chen, Jianzhong,Fu, Guanghong,Liu, Delong,Liu, Yangang,Zhang, Wanbin
supporting information, p. 6839 - 6844 (2013/07/26)
(S)-C10-BridgePHOS was successfully applied to a highly efficient Pd-catalyzed enantioselective hydrogenation of substituted indoles. The methodology was suitable for the hydrogenation of indoles substituted at the 2-, 3- and 2,3-positions. Products were obtained in quantitative conversion and up to 98% ee. The role the 2-position substituent plays in the hydrogenation process has been proposed. The methodology could be used as an alternative method to synthesize extremely important chiral indolines from N-unprotected indoles.
A microwave-assisted, propylphosphonic anhydride (T3P) mediated one-pot Fischer indole synthesis
Desroses, Matthieu,Wieckowski, Krzysztof,Stevens, Marc,Odell, Luke R.
supporting information; experimental part, p. 4417 - 4420 (2011/09/19)
A rapid, mild, and high yielding protocol for the Fischer indolization of arylhydrazines with T3P under microwave irradiation is described. Significant features of this method include short reaction times and preparative ease.
Synthesis and reactions of 4-hydroxy-8,9,10, 11-tetrahydropyrido[3,2,1-jk] carbazol-6-ones
Stadlbauer, Wolfgang,Van Dang, Hoai,Berger, Birgit S.
experimental part, p. 807 - 824 (2010/08/20)
(Chemical Equation Presented) Tetrahydrocarbazoles 4 obtained from phenylhydrazines and cyclohexanones gave by cyclocondensation with 2-substituted malonates 5 in all cases 4-hydroxy-8,9,10,11-tetrahydropyrido [3,2,1-jk]carbazol-6-ones 6 by attack at the nitrogen and the aromatic ring of tetrahydrocarbazoles 4; the direction of the cyclization was not dependent on substituents either in the aromatic or the saturated ring; isomeric pyridocarbazoles could not be isolated. Electrophilic substitutions of pyridocarbazoles 6 under mild conditions took place exclusively at the 5-position and gave pyridocarbazolediones 9-11 with 5-nitro-, 5-hydroxy or 5-chloro-substituents. Exchange of the chloro substituent in 11 gave 5-azido- and 5-amino products 12, 14 or 16. Reactions at the aromatic ring were not observed. Chlorination of 4-hydroxypyridocarbazoles 6 with phosphoryl chloride by nucleophilic substitution took place exclusively at the 4-position and gave 4-chloropyridocarbazolones 17, which were further reacted to azides and amines 18, 19.
Efficient and straightforward synthesis of tetrahydrocarbazoles and 2,3-dimethyl indoles catalyzed by CAN
Varma, P. Prabhakara,Sherigara, Bailure S.,Mahadevan, Kittapa M.,Hulikal, Vijaykumar
experimental part, p. 158 - 165 (2009/04/07)
A simple protocol was established to synthesize 2,3-dialkyl indoles and various tetrahydrocarbazoles via Fischer indole synthesis. This method uses ceric ammonium nitrate as a catalyst for the Fischer indole synthesis with substituted phenyl hydrazine hydrochlorides and 2-butanone, phenyl propanal, and cyclohexanone. This process is a practical synthetic method for the preparation of various 2,3-disubstituted alkyl indoles and tetrahydrocarbazoles. Copyright Taylor & Francis Group, LLC.
Antimony (III) sulfate catalyzed one-pot synthesis of 2,3- disubstitutedindoles
Srinivasa,Mahadevan,Varma, P. Prabhakara,Sudhakara
experimental part, p. 1843 - 1853 (2010/02/28)
A novel one-pot Fischer indole synthesis approach has been developed by using antimony (III) sulfate as the catalyst. Good yields were obtained after reacting phenylhydrazines hydrochlorides and ketones in refluxing methanol. The exclusive formation of 2,3- disubstituted indoles was observed in the reaction of ethyl methyl ketone with phenylhydrazines. One-pot synthesis of indole-3-propanol using dihydropyran has also been described. The use of reusable antimony (III) sulfate as a catalyst makes this method both economically and environmentally friendly.
Bismuth nitrate promoted fischer indole synthesis: A simple and convenient approach for the synthesis of alkyl indoles
Sudhakara, Aralihalli,Jayadevappa, Honnali,Kumar, Hosanagara N.H.,Mahadevan, Kittappa M.
scheme or table, p. 159 - 164 (2010/04/23)
A novel one-pot fisher indole synthesis approach has been developed by using bismuth nitrate as a catalyst. Yields around 90-95% were obtained after reaction in methanol at reflux temperature in 20-40 min. Apart from the mild reaction conditions of the process and its excellent results, the simplicity of product isolation and the possibility to recycle the bismuth nitrate offers a significant advantage.
