Boron Trifluoride‐Catalyzed Synthesis of 3‐Alkylidene‐3H‐indole N‐Oxides via Tandem Reaction of Propargylic Alcohols and Nitrosobenzenes

Muthusamy, Sengodagounder; Balasubramani, Alagesan; Suresh, Eringathodi

doi:10.1002/adsc.201601151

Cited by 28 publications

(2 citation statements)

References 32 publications

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“…By using nitrosobenzenes 138 instead of azides to perform the reaction with propargylic alcohols 1 , the functionalized 3‐alkylidene‐3 H ‐indole N ‐oxides 139 , which were intriguing skeletons bearing significantly biological activities, were successfully be formed in good to excellent yields under mild conditions (Scheme 54). [73] Various tertiary propargylic alcohols bearing alkyl or aryl substitutes were compatible with this transformation. In this case, the generated intermediate A underwent intramolecular cyclization to give the final product 139 .…”

Section: Reactions Involving N P‐nucleophiles To Capture Allenyl Carmentioning

confidence: 98%

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

2020

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Heterocyclic compounds are important organic compounds and have emerged as key scaffolds in numerous drugs, natural products, vitamins, biologically and pharmaceutically active compounds. Over the past few decades, the development of versatile methodologies employing propargylic alcohols as synthons for the construction of heterocyclic skeletons has attracted great attention from synthetic chemists. In this review, recent developments in the cascade cyclization of propargylic alcohols with diverse nucleophiles to construct heterocyclic compounds are summarized. According to the types of nucleophiles, these reactions can be divided into four categories: 1) Reactions involving C‐nucleophiles to capture allenyl carbocation; 2) Reactions involving O, S‐nucleophiles to capture allenyl carbocation; 3) Reactions involving N, P‐nucleophiles to capture allenyl carbocation; 4) Reactions involving halo‐nucleophiles to capture allenyl carbocation.

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Section: Reactions Involving N P‐nucleophiles To Capture Allenyl Carmentioning

confidence: 98%

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

2020

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“…The synthesis of 3‐alkylidene‐3 H ‐indole N ‐oxides 61 has been described through a tandem reaction of propargylic alcohols and nitrosobenzenes catalyzed by boron trifluoride etherate in the presence of CH 2 Cl 2 at 0 °C (Scheme 42). [94] The mechanism included the formation of propargyl and allenic carbocation by the reaction of boron trifluoride etherate with propargylic alcohols. The nitrosobenzene attacks the less sterically hindered allenic carbocation, followed by a Friedel‐Crafts cyclization and deprotonation leading to the product (Scheme 42).…”

Section: Synthesis Of 3h‐indolesmentioning

confidence: 99%

Recent Developments in the Cyclization of Alkynes and Nitrogen Compounds for the Synthesis of Indole Derivatives

Neto

Zeni

2021

Asian J Org Chem

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This review is intended to highlight the most useful approaches for the synthesis of indole derivatives (azaindoles, carbazoles, carbolines, indazoles, 3H-indoles, indolines, indolizines, isoindoles, and isoindolines), which were described by using transition-metal catalyzed cyclization reactions of alkynes and nitrogen compounds. The methodologies carried out under metal-free conditions will also be illustrated herein. This review will cover the data published mostly in the past decade. Synthesis of 6-AzaindolesAzaindoles, although rare in nature, have attracted a significant attention because some synthetic structures containing this nucleus exhibit biological activities. [17] The synthetic methods describing the preparation of azaindoles are limited. Usually their synthesis was achieved from the cyclization reaction of substrates containing aminopyridines. [18] Transition Metal-Free Synthesis of 6-AzaindolesWe have nominated two methodologies for the preparation of 6-azaindoles, which were developed using alkynes and nitrogen compounds in a metal-free protocol. In the first, an electrophilic cyclization condition, using iodine as an electrophilic source, was applied to 2-(azidomethyl)-3-alkynyl-pyrroles in the preparation of 4-iodo-6-azaindoles 1 (Scheme 1, eq 1). [19] The second approach described the preparation of 2,5-disubstituted 6azaindoles 2 from base-catalyzed intramolecular cyclization of 2-(azidomethyl)-3-alkynyl-pyrroles (Scheme 1, eq 2). [20] 3. Synthesis of 7-Azaindoles Transition Metal-Catalyzed Synthesis of 7-Azaindoles Silver-Catalyzed Synthesis of 7-AzaindolesSilver-catalyzed cyclization reactions of alkynes constitute powerful strategies for the construction of heterocycles. In particular, the 7-azaindoles could be obtained by these approaches. A general method for the preparation of aryl-[a] Dr. J.

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Lewis Acid‐Catalyzed [4+2] Annulation between Propargylic Alcohols with Benzo[d]isoxazoles

Han

Sun

et al. 2017

Adv Synth Catal

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An unprecedented copper(II) trifluoromethanesulfonate-catalyzed [4+ +2] cascade annulation of propargylic alcohols with benzo[d]isoxazoles proceeds throughasequential ring opening/Meyer-Schuster rearrangement/intermolecular cyclization. This protocol, which toleratesabroad variety of functional groups,o ffersaversatile, modular and atom-economicala ccess to an ew class of fascinating quinolined erivatives in good yields under mild conditions.T he transformation could be scaledu p to ag ram scale efficiently,t hus highlighting the synthetic utility of this methodology.

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Boron Trifluoride‐Catalyzed Synthesis of 3‐Alkylidene‐3H‐indole N‐Oxides via Tandem Reaction of Propargylic Alcohols and Nitrosobenzenes

Cited by 28 publications

References 32 publications

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

Recent Developments in the Cyclization of Alkynes and Nitrogen Compounds for the Synthesis of Indole Derivatives

Lewis Acid‐Catalyzed [4+2] Annulation between Propargylic Alcohols with Benzo[d]isoxazoles

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