Cascade cyclization for the synthesis of indolo[2,1-α]isoquinoline derivatives <i>via</i> visible-light-induced halogen-atom-transfer (XAT) and hydrogen-atom-transfer (HAT)

Ma, Na; Guo, Lin; Shen, Zheng‐Jia; Qi, Dan; Yang, Chao; Xia, Wujiong

doi:10.1039/d1ob02480a

Cited by 27 publications

(6 citation statements)

References 59 publications

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“…Such a strategy was elegantly developed by Doyle, [25] and recently employed by the Xia group in 2022 for the synthesis of indolo[2,1‐α]isoquinoline derivatives via the cascade formation of a C( sp 3 )–C( sp 3 ) and C( sp 3 )–C( sp 2 ) bonds (Scheme 11). [26] …”

Section: C(sp3)–c(sp3) Bond Formationmentioning

confidence: 99%

An Overview of α‐Aminoalkyl Radical Mediated Halogen‐Atom Transfer

2023

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The merging of photocatalysis with halogen‐atom transfer (XAT) processes has proven to be a versatile tool for the generation of carbon‐centered radicals in organic synthesis. XAT processes are unique in that they generate radicals without requiring the use of strong reductants necessary for the traditional single electron transfer (SET) activation of halides. Pathways to achieve XAT in synthetic applications can be categorized into three major sections: i) heteroatom‐based activators, ii) metal‐based activators, and iii) carbon‐based activators among which α‐aminoalkyl radicals have taken the center stage. Access to these α‐aminoalkyl radicals as XAT reagents has gained significant attention in the past few years due to the robustness of the reactions, the simplicity of the reagents required, and the broadness of their applications. Generation of these α‐aminoalkyl radicals is simply achieved through the single electron oxidation of tertiary amines, which after deprotonation at the α‐position generates the α‐aminoalkyl radicals. Due to the wide scope of tertiary amines available and the tunable nucleophilicity of α‐aminoalkyl radical formed, this strategy has become an attractive alternative to heteroatom/metal‐based radicals for XAT. In this minireview, we focus our attention on recent (2020‐2023) developments and uses of this robust technology to mediate XAT processes.

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Section: C(sp3)–c(sp3) Bond Formationmentioning

confidence: 99%

An Overview of α‐Aminoalkyl Radical Mediated Halogen‐Atom Transfer

2023

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“…In 2022, Xia and co‐workers reported a visible‐light‐induced metal‐free cascade cyclization for selective synthesis of substituted indolo[2,1‐ a ]isoquinoline derivatives via either halogen‐atom‐transfer (XAT) or the hydrogen‐atom‐transfer (HAT) process (Scheme 79). [141] Mechanically, in the XAT process, single‐electron‐transfer between excited state eosin Y* and tert‐ butyl hydroperoxide (TBHP) gives t BuO⋅⋅radical. Next, the hydrogen atom transfer from TBHP to t BuO⋅⋅radical affords the t BuOO⋅⋅radical, which abstracts a hydrogen atom from tertiary amine to form the α‐aminoalkyl radical.…”

Section: Cyclization Of Alkene‐tethered 2‐arylindoles and 2‐aryl Benz...mentioning

confidence: 99%

Radical Cascade Cyclization of Alkene‐Tethered Compounds: Versatile Approach towards Ring‐Fused Polycyclic Structures

Liu

Wang

2023

Asian J Org Chem

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Ring-fused polycyclic structures widely exist in a myriad of natural products and pharmaceutical molecules. Consequently, the construction of such structures from readily available substrates becomes an important researching topic in organic synthesis. Triggered by the addition of radicals to the (activated or unactivated) double bonds in alkenes, the subsequent intramolecular addition/cyclization leads to polycyclic compounds. Following this procedure, a variety of functionalized ring-fused structures were formed. Great achievements have been witnessed recently. Those works provided efficient, atom economy, and operational simple approaches toward versatile functionalized polycyclic structures from readily available alkene-based substrates.Here, we summarized the recent achievements on the formation of ring-fused polycyclic structures via the radicaltriggered cascade reactions of alkenes. Construction of polycyclic structures with no less than 3 fused rings developed during the last decade were included in this Review, corresponding mechanisms were also discussed.

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“…Ma et al employed halogen-atom transfer (XAT) and hydrogen-atom transfer (HAT) approaches to induce a radical cascade cyclization reaction for the synthesis of indolo[2,1- a ]isoquinoline scaffolds 170 and 171 (Scheme 34). 78 In HAT, the aryl radical generated from PMPN 2 BF 4 by the reductive single electron transfer reacts with alkyl halide 168 to form an α-alkyl halide radical, which on radical addition to the olefin 167 forms alkyl radical intermediate 169 that on subsequent cyclization and deprotonation affords 170 . In the XAT mechanism, the radical cyclization is induced by the alkyl radical generated by the tertiary amine radical to afford compound 171 .…”

Section: Organocatalytic Reactionsmentioning

confidence: 99%

Diversely functionalized isoquinolines and their core-embedded heterocyclic frameworks: a privileged scaffold for medicinal chemistry

Vijayakumar,

Manod,

Krishna

et al. 2023

RSC Med. Chem.

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Cascade cyclization for the synthesis of indolo[2,1-α]isoquinoline derivatives via visible-light-induced halogen-atom-transfer (XAT) and hydrogen-atom-transfer (HAT)

Abstract: A transition metal-free photoredox cascade cyclization is herein reported. In this protocol, sustainable visible light was used as energy source and organic light-emitting molecule Eosin Y served as efficient photocatalyst....

Cited by 27 publications

References 59 publications

An Overview of α‐Aminoalkyl Radical Mediated Halogen‐Atom Transfer

An Overview of α‐Aminoalkyl Radical Mediated Halogen‐Atom Transfer

Radical Cascade Cyclization of Alkene‐Tethered Compounds: Versatile Approach towards Ring‐Fused Polycyclic Structures

Diversely functionalized isoquinolines and their core-embedded heterocyclic frameworks: a privileged scaffold for medicinal chemistry

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