Catalytic hydrative cyclization of aldehyde-ynamides with water for synthesis of medium-sized lactams

Zhu, Bo‐Han; Zheng, Yan-Xin; Kang, Wei; Deng, Cunbao; Zhou, Jin‐Mei; Ye, Long‐Wu

doi:10.1007/s11426-021-1069-7

Cited by 21 publications

(2 citation statements)

References 56 publications

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“…All commercially available reagents were used without further purification. Spiroindolines were prepared according to the known procedure …”

Section: Methodsmentioning

confidence: 99%

“…Recently, we have developed a diastereoselective protocol to prepare indole-annulated eight-membered lactams through light-driven alkylative ring-opening of spiroindolines, a type of dearomative Heck product of easily available β-carbolines . DFT calculations and mechanistic experiments support that a cationic C–C fragmentation should be favorable rather than a homolytic C–C fragmentation, in which a tertiary cation intermediate might be involved (Scheme a) .…”

Section: Introductionmentioning

confidence: 99%

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Access to Indole-Annulated Medium-Sized Lactams through Protonation/Deuteration-Induced Ring-Opening of Spiroindolines

2021

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A protocol has been developed to access indoleannulated eight-and nine-membered lactams through protonationinduced ring-opening of spiroindolines, which are dearomative Heck products of tetrahydro-β-carbolines or hexahydroazepino [3,4-b]indoles. Brønsted acids and nucleophiles were explored and compared in the transformation. A combination of deuterated hydrochloride and deuterated methanol enables deuterative ring-opening of spiroindolines to afford medium-sized lactam diastereoisomers with a deuterium content ratio around 1:1. ■ INTRODUCTIONIndole-annulated medium-sized nitrogen-containing heterocyclic rings are core structures embedded in bioactive natural alkaloids, including balasubramide, 1 deoxyisoaustamide, 2 okaramine, 3 lundurine A−D, 4 and vinblastine. 5 Generally, the construction of medium-sized compounds has been challenging in organic synthesis due to unfavorable entropy and transannular interactions. 6 It is impressive that significant strategies including cycloaddition, 7 cycloisomerization, 8 and ring expansion 9 have been invented for the generation of eightand nine-membered nitrogen-containing heterocycles.Recently, we have developed a diastereoselective protocol to prepare indole-annulated eight-membered lactams through light-driven alkylative ring-opening of spiroindolines, a type of dearomative Heck product of easily available β-carbolines. 10 DFT calculations and mechanistic experiments support that a cationic C−C fragmentation should be favorable rather than a homolytic C−C fragmentation, in which a tertiary cation intermediate might be involved (Scheme 1a). 11 Because a tertiary carbon cation could be formed regioselectively through direct protonation of an alkene, we envisioned an alternative to indole-annulated medium-sized lactams by protonationinduced ring-opening of the spiroindolines (Scheme 1b).The key issues of the transformation include the choice of Brønsted acids, the tolerance of the indole ring, and the nucleophile to trap the iminium intermediate. Furthermore, if this can be realized, a deuterative ring-opening would be feasible by employing deuterated acids and deuterated nucleophiles, which provides an unprecedented protocol to prepare deuterated indole-containing medium-sized hetero-

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“…All commercially available reagents were used without further purification. Spiroindolines were prepared according to the known procedure …”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Access to Indole-Annulated Medium-Sized Lactams through Protonation/Deuteration-Induced Ring-Opening of Spiroindolines

2021

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Cobalt‐Catalyzed Cascade Reaction of Ynamides and 1,3‐Dicarbonyl Compounds for Selective Synthesis of Differently SizedN‐Heterocycles

et al. 2023

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A triphenylphosphine‐ligated cobalt‐catalyzed cyclization manifold with various 1,3‐dicarbonyl compounds and halogenated N‐allyl ynamides was accomplished under alkaline reaction conditions, facilitating the synthesis of differently sized N‐heterocycles. A large array of products was prepared to demonstrate the selective synthesis of N‐heterocycles of different ring sizes (5‐, 6‐, and 7‐membered rings) via cobalt catalysis. The reaction has broad substrate scope and a wide range of functional groups.

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Efficient Synthesis of Medium‐sized Nitrogen Heterocycles by Brønsted Acid‐Catalyzed Cyclization of Ene‐ynamides

et al. 2023

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A Brønsted acid‐catalysed cyclization of ene‐ynamides has been developed to construct 7‐ or 8‐membered azacycles in good to high yields. The use of a simple C=C double bond as a nucleophile enables the synthesis of medium‐sized ring from an acyclic ynamide. This reaction system features simple and mild reaction conditions without any metal catalysts, and no requirement of high dilution for medium‐sized ring formation. This method is applicable to a variety of substituents on the ynamides, such as alkyl, aryl, acetylene and silyloxy group.

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Catalytic hydrative cyclization of aldehyde-ynamides with water for synthesis of medium-sized lactams

Cited by 21 publications

References 56 publications

Access to Indole-Annulated Medium-Sized Lactams through Protonation/Deuteration-Induced Ring-Opening of Spiroindolines

Access to Indole-Annulated Medium-Sized Lactams through Protonation/Deuteration-Induced Ring-Opening of Spiroindolines

Cobalt‐Catalyzed Cascade Reaction of Ynamides and 1,3‐Dicarbonyl Compounds for Selective Synthesis of Differently SizedN‐Heterocycles

Efficient Synthesis of Medium‐sized Nitrogen Heterocycles by Brønsted Acid‐Catalyzed Cyclization of Ene‐ynamides

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