99290-14-9Relevant academic research and scientific papers
Rhodium-Catalyzed Annulation of N-Acetoxyacetanilide with Substituted Alkynes: Conversion of Nitroarenes to Substituted Indoles
Ghorai, Jayanta,Ramachandran, Kuppan,Anbarasan, Pazhamalai
, p. 14812 - 14825 (2021/10/25)
A general and efficient rhodium-catalyzed redox-neutral annulation of N-acetoxyacetanilides, readily accessible from nitroarenes, with alkynes has been accomplished for the synthesis of substituted indole derivatives. A wide range of substituted 2,3-diarylindoles were achieved from various substituted N-acetoxyacetanilides and symmetrical/unsymmetrical alkynes in good to excellent yields. The developed method was successfully integrated with the synthesis of N-acetoxyacetanilides for the efficient one-pot synthesis of indoles from nitroarenes. The important features are the introduction of N-acetoxyacetamide as a new directing group, redox-neutral annulation, an additive-free approach, wide functional group tolerance, an intramolecular version, and a one-pot reaction of nitroarenes. The method was further extended to the synthesis of potent higher analogues of indole, viz., pyrrolo[3,2-f]indoles and dibenzo[a,c]carbazoles. In addition, a plausible mechanism was proposed based on the isolation and stoichiometric study of a potential aryl-Rh intermediate.
Mechanochemical indole synthesis by rhodium-catalysed oxidative coupling of acetanilides and alkynes under solventless conditions in a ball mill
Hermann, Gary N.,Jung, Celine L.,Bolm, Carsten
supporting information, p. 2520 - 2523 (2017/07/17)
A mechanochemical indole synthesis by rhodium(iii)-catalysed C-H bond functionalisation in a planetary mill has been developed. It occurs in the absence of any solvent, does not require additional heating and only needs catalytic quantities of Cu(OAc)2 in combination with dioxygen as a terminal oxidant. Accordingly, the process represents a powerful and environmentally benign alternative to the common solution-based standard protocols.
Combining Zn ion catalysis with homogeneous gold catalysis: An efficient annulation approach to N-protected indoles
Wang, Yanzhao,Liu, Lianzhu,Zhang, Liming
, p. 739 - 746 (2013/03/13)
The Fischer indole synthesis is perhaps the most powerful method for indole preparation, but it often suffers from low regioselectivities with unsymmetrical aliphatic ketone substrates and strongly acidic conditions and is not suitable for α,β-unsaturated ketones. In this edge article, we disclose an efficient synthesis of N-protected indoles from N-arylhydroxamic acids/N-aryl-N-hydroxycarbamates and a variety of alkynes via cooperative gold and zinc catalysis. The zinc catalysis is similar to the related zinc ion catalysis in metalloenzymes such as human carbonic anhydrase II and substantially enhances the O-nucleophilicity of N-acylated hydroxylamine by forming the corresponding Zn chelates. The Zn chelates can attack gold-activated alkynes to form O-alkenyl-N-arylhydroxamates, which can undergo facile 3,3-sigmatropic rearrangements and subsequent cyclodehydrations to yield N-protected indole products. This new chemistry offers several important improvements over the Fischer indole synthesis: (a) the reaction conditions are mildly acidic and can tolerate sensitive groups such as Boc; (b) broader substrate scopes including substrates with pendant carbonyl groups (reactive in the Fischer chemistry) and alkyl chlorides; (c) better regioselectivities for the formation of 2-substituted indoles under much milder conditions; (d) 2-alkenylindoles can be prepared readily in good to excellent yields, for which Fischer chemistry could not be used; (e) with internal alkynes both steric and electronic controls are available for achieving good regioselectivities, while Fischer chemistry is in general problematic. The Royal Society of Chemistry 2013.
Nuclear Magnetic Resonance: Part IV - Carbon-13 NMR Spectral Studies on Substituted 1-Acetylindoles
Biswas, K. M.,Dhara, R. N.,Mallik, Haimanti,Roy, Sumita
, p. 654 - 656 (2007/10/02)
1-Acetyl-3-methylindole (1), 1-acetyl-3-ethylindole (2), 1-acetyl-3-phenylindole (3),1-acetyl-2,3-dimethylindole (4), 1-acetyl-3-methyl-2-phenylindole (5), 1-acetyl-3-ethyl-2-phenylindole (6), 1-acetyl-2,3-diphenylindole (7),1-acetyl-5-methyl-2,3-diphenylindole (8) and 3-hydroxy-3-methyl-2-phenyl-3H-indole-1-oxide (9) have been prepared and their carbon-13 NMR spectra recorded.The methyl carbon signals of the acetyl group of 2-substituted 1-acetylindoles (4-8) undergo downfield shift (ca. Δδ = 5 ppm) in comparison to those of the same carbons of the 2-unsubstituted1-acetylindoles (1-3) showing that the former compounds exist entirely in the E-conformation and the latter solely in the Z-conformation at the ambient temperature.This is confirmed by the fact that the carbonyl carbons and the methyl carbons of the acetyl groups of 1-8 gives rise to only one signal each.The signals due to C-3, C-6 and C-7 of 1-8 appear downfield (Δδ = 3.64 to 9.56 ppm) as compared to those of the same carbons of the corresponding indoles and 1-methylindoles, but C-9 signals of 1-8 undergo upfield shift (Δδ = 0.66 to 4.62 ppm) as compared to C-9 signal of the latter compounds.Moreover, the carbonyl carbon signals of 1-8 appear downfield (ca. ΔSd = 10 ppm) in comparison to those of the same carbon of the corresponding indole-1-carboxaldehydes.
