Intramolecular addition of diarylmethanols to imines promoted by KOt-Bu/DMF: a new synthetic approach to indole derivatives

Chen, Jiahua; Chen, Zicong; Zhang, Hong; Zhang, Ting; Wang, Wei‐juan; Zou, Yong; Zhang, Xue‐Jing; Yan, Ming

doi:10.1039/c6ob00423g

Cited by 17 publications

(9 citation statements)

References 67 publications

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“…The formation of a stabilized radical at the benzylic position in the presence of DMF/ t -BuOK was confirmed by successful trapping of this species with TEMPO, a common trapping reagent for free radicals (Scheme , eq 5) . A Br-containing substrate, 1f , was prepared to investigate the ability of these reagents to undergo SET, and under our conditions, 2f was formed along with dehalogenated product 2d in about a ∼3:1 ratio (Scheme , eq 6).…”

Section: Mechanistic Studiesmentioning

confidence: 92%

Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp³)–H Aminations with Unprotected Anilines

et al. 2017

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An intramolecular oxidative C(sp)-H amination from unprotected anilines and C(sp)-H bonds readily occurs under mild conditions using t-BuOK, molecular oxygen and N,N-dimethylformamide (DMF). Success of this process, which requires mildly acidic N-H bonds and an activated C(sp)-H bond (BDE < 85 kcal/mol), stems from synergy between basic, radical, and oxidizing species working together to promote a coordinated sequence of deprotonation: H atom transfer and oxidation that forges a new C-N bond. This process is applicable for the synthesis of a wide variety of N-heterocycles, ranging from small molecules to extended aromatics without the need for transition metals or strong oxidants. Computational results reveal the mechanistic details and energy landscape for the sequence of individual steps that comprise this reaction cascade. The importance of base in this process stems from the much greater acidity of transition state and product for the 2c,3e C-N bond formation relative to the reactant. In this scenario, selective deprotonation provides the driving force for the process.

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Section: Mechanistic Studiesmentioning

confidence: 92%

Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp³)–H Aminations with Unprotected Anilines

et al. 2017

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“…Following General Procedure A, aniline TMP-aa1 56 [(2-aminophenyl)(phenyl)methanol] (150 mg, 0.753 mmol, 1.05 equiv) and (E)-2-(2-(4-methoxystyryl)-1H-indol-3-yl)acetaldehyde (209 mg, 0.717 mmol, 1.00 equiv) were coupled. Silica gel chromatography with hexanes-MTBE (5:1 to 3:1) gave a yellow foam.…”

Section: (E)-(2-((2-(2-(4-methoxystyryl)-1h-indol-3-yl)ethyl)amino)phenyl)(phenyl)methanol (13d)mentioning

confidence: 99%

Asymmetric Synthesis of Fused Tetrahydroquinolines via Intramolecular Aza-Diels–Alder Reaction of ortho-Quinone Methide Imines

Hofmann¹,

Gärtner²,

Kretzschmar³

et al. 2021

Synthesis

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Aza-Diels Alder reactions are straightforward processes in the construction of N-heterocycles, featuring inherent atom-economy and stereospecificity. Intramolecular strategies allow formation of bicyclic core structures with up to three stereocenters within a single step. Herein, this concept is combined with the chemistry of chiral Brønsted acid-bound ortho-quinone methide imines generating a range of interesting fused tetrahydro-quinolines in a diastereo- and enantioselective manner.

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“…13 (2-Aminophenyl)(phenyl)methanone (4a) was prepared using known literature protocol. 32 (E)-1-(2-Aminophenyl)-3-phenylprop-2-en-1-one (4b) was prepared using known literature protocol. 33 2-Aminobenzaldehyde (4c) was prepared using known literature protocol.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Three-Component Approach to Pyridine-Stabilized Ketenimines for the Synthesis of Diverse Heterocycles

2019

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Ketenimines are versatile synthetic intermediates capable of performing novel transformations in organic synthesis. They are normally generated in situ due to their inherent instability and high level of reactivity. Herein, we report pyridine-stabilized ketenimine zwitterionic salts, which are prepared through click chemistry from readily accessible alkynes and sulfonyl azides. To demonstrate their synonymous reactivity to ketenimines, these salts have been utilized in a cascade sequence to access highly functionalized quinolines including the core structures of an antiprotozoal agent and the potent topoisomerase inhibitor Tas-103.

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Intramolecular addition of diarylmethanols to imines promoted by KOt-Bu/DMF: a new synthetic approach to indole derivatives

Abstract: KOt-Bu/DMF promoted intramolecular addition of diarylmethanols to imines was developed. A series of 2,3-disubstituted indoles was obtained in good yields. A reaction mechanism of radical cyclization and subsequent dehydration is proposed.

Cited by 17 publications

References 67 publications

Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp³)–H Aminations with Unprotected Anilines

Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp³)–H Aminations with Unprotected Anilines

Asymmetric Synthesis of Fused Tetrahydroquinolines via Intramolecular Aza-Diels–Alder Reaction of ortho-Quinone Methide Imines

Three-Component Approach to Pyridine-Stabilized Ketenimines for the Synthesis of Diverse Heterocycles

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Intramolecular addition of diarylmethanols to imines promoted by KOt-Bu/DMF: a new synthetic approach to indole derivatives

Abstract: KOt-Bu/DMF promoted intramolecular addition of diarylmethanols to imines was developed. A series of 2,3-disubstituted indoles was obtained in good yields. A reaction mechanism of radical cyclization and subsequent dehydration is proposed.

Cited by 17 publications

References 67 publications

Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp3)–H Aminations with Unprotected Anilines

Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp3)–H Aminations with Unprotected Anilines

Asymmetric Synthesis of Fused Tetrahydroquinolines via Intra­molecular Aza-Diels–Alder Reaction of ortho-Quinone Methide Imines

Three-Component Approach to Pyridine-Stabilized Ketenimines for the Synthesis of Diverse Heterocycles

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Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp³)–H Aminations with Unprotected Anilines

Coupling N–H Deprotonation, C–H Activation, and Oxidation: Metal-Free C(sp³)–H Aminations with Unprotected Anilines

Asymmetric Synthesis of Fused Tetrahydroquinolines via Intramolecular Aza-Diels–Alder Reaction of ortho-Quinone Methide Imines