Synthesis of Indoles by Conjugate Addition and Ligand‐Free Copper‐Catalyzed Intramolecular Arylation of Activated Acetylenes with <i>o</i>‐Haloanilines

Gao, Detian; Parvez, Masood; Back, Thomas G.

doi:10.1002/chem.201002628

Cited by 28 publications

(15 citation statements)

References 35 publications

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“…The yields of the products 3 and 14 are provided in Table 1 and those of the 2‐unsubstituted and 2‐phenyl indole derivatives 15 and 16 are shown in Scheme . Characterization data and copies of 1 H and 13 C NMR spectra of indoles 4 a , 4 c – 4 g , 4 i – 4 l , 14 m – 14 o , 15 , and 16 are provided in the Supporting Information of our preliminary communication 19. The characterization data and spectra of the remaining indoles 4 h and 4 q that are in Table 1 are described in the accompanying Supporting Information.…”

Section: Methodsmentioning

confidence: 99%

“…Typical preparation of 26 and 31 : The preparation of indoles 26 b , 26 c , and 31 a – 31 d was performed similarly to that described for sulfonyl enamines 3 , with any minor changes indicated in Scheme and Table 4. Characterization data and copies of 1 H and 13 C NMR spectra of indoles 26 b , 26 c , and 31 a – 31 d were provided in the Supporting Information of our preliminary communication 19. Characterization data and spectra for 27 are provided in the accompanying Supporting Information.…”

Section: Methodsmentioning

confidence: 99%

“…Characterization data and copies of 1 H and 13 C NMR spectra of indoles 4 a, 4 c-4 g, 4 i-4 l, 14 m-14 o, 15, and 16 are provided in the Supporting Information of our preliminary communication. [19] The characterization data and spectra of the remaining indoles 4 h and 4 q that are in Table 1…”

Section: Preparation Of 14mentioning

confidence: 99%

“…Characterization data and copies of 1 H and 13 C NMR spectra of indoles 23 a, 23 b, and 23 d-23 i were provided in the Supporting Information of our preliminary communication. [19] Characterization data and spectra of indole 23 c are provided in the accompanying Supporting Information.…”

Section: Typical Preparation Of 22mentioning

confidence: 99%

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Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Gao

Back

2012

Chemistry A European J

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A versatile new synthesis of indoles was achieved by the conjugate addition of N-formyl-2-haloanilines to acetylenic sulfones, ketones, and esters followed by a copper-catalyzed intramolecular C-arylation. The conjugate addition step was conducted under exceptionally mild conditions at room temperature in basic, aqueous DMF. Surprisingly, the C-arylation was performed most effectively by employing copper(II) acetate as the catalyst in the absence of external ligands, without the need for protection from air or water. An unusual feature of this process, for the case of acetylenic ketones, is the ability of the initial conjugate-addition product to serve as a ligand for the catalyst, which enables it to participate in the catalysis of its further transformation to the final indole product. Mechanistic studies, including EPR experiments, indicated that copper(II) is reduced to the active copper(I) species by the formate ion that is produced by the base-catalyzed hydrolysis of DMF. This process also served to recycle any copper(II) that was produced by the adventitious oxidation of copper(I), thereby preventing deactivation of the catalyst. Several examples of reactions involving acetylenic sulfones attached to a modified Merrifield resin demonstrated the feasibility of solid-phase synthesis of indoles by using this protocol, and tricyclic products were obtained in one pot by employing acetylenic sulfones that contain chloroalkyl substituents.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Preparation Of 14mentioning

confidence: 99%

Section: Typical Preparation Of 22mentioning

confidence: 99%

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Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Gao

Back

2012

Chemistry A European J

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“…Iodoaniline derivative 247 was cyclized under the action of copper diacetate with the formation of 2,3‐dihydro‐1 Н ‐pyrrolo[1,2‐ a ]indole 248 a isolated in a high yield (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Some Biological Properties of Pyrrolo[1,2‐a]indoles

Monakhova

Ryabova

Makarov

2015

Journal of Heterocyclic Chem

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Indoles via Palladium‐Catalyzed Cyclization

2011

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The palladium‐catalyzed assembly of the functionalized pyrrole nucleus on a benzenoid scaffold is a widley used synthetic tool for the preparation of indole derivatives. This construction can be categorized into four main types: (1) cyclization of alkynes; (2) cyclization of alkenes; (3) cyclization via C ‐vinyl reactions; and (4) cyclization via N − arylation or N − vinylation reactions. The first approach is the most versatile in terms of range of the added functional groups and of the bonds that can be created in the construction of the pyrrole ring. This method is based on the utilization of precursors containing nitrogen nucleophiles and carbon‐carbon triple bonds. The nitrogen nucleophile and alkyne moiety may be part of the same molecule or belong to two different molecules. Some of the most general cyclizations of indoles are summarized. Alkene‐based cyclizations to give indoles are also summarized. Cyclization to indoles via arene vinylation has limited synthetic scope. Indoles can be prepared via cyclizations proceeding through N ‐arylation and N‐vinylation reactions based on pioneering work. In general, only synthetic procedures where palladium catalysis is involved in the pryrrole ring construction event are discussed in this chapter.

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Synthesis of Indoles by Conjugate Addition and Ligand‐Free Copper‐Catalyzed Intramolecular Arylation of Activated Acetylenes with o‐Haloanilines

Cited by 28 publications

References 35 publications

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Indole Synthesis by Conjugate Addition of Anilines to Activated Acetylenes and an Unusual Ligand‐Free Copper(II)‐Mediated Intramolecular Cross‐Coupling

Synthesis and Some Biological Properties of Pyrrolo[1,2‐a]indoles

Indoles via Palladium‐Catalyzed Cyclization

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