Intramolecular (4+3) Cycloadditions of Oxidopyridinium Ions: Towards Daphnicyclidin A

Tu, Jianzhuo; Ripa, Rawshan A.; Kelley, Steven P.; Harmata, Michael

doi:10.1002/chem.202200370

Cited by 8 publications

(4 citation statements)

References 35 publications

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“…As a final example, Harmata and co-workers recently developed the synthesis of the ABC ring system of daphnicyclidin A using an intramolecular [4 + 3] cycloaddition reaction of an oxidopyridinium ion ( Scheme 230 ). 302 Initially, the authors studied substrates with a three-carbon tether attached to the pyridinium ion. Thus, heating pyridinium substrates 476 , with dienes substituted at the C2-position, in the presence of Et 3 N as a base, triggered an intramolecular (4 + 3) cycloaddition to render a mixture of endo 477 and exo 477′ tricycles in good yields.…”

Section: Applications To Natural Product Synthesismentioning

confidence: 99%

Recent Strategies in the Nucleophilic Dearomatization of Pyridines, Quinolines, and Isoquinolines

Escolano,

Gaviña,

Alzuet-Piña

et al. 2024

Chem. Rev.

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Dearomatization reactions have become fundamental chemical transformations in organic synthesis since they allow for the generation of three-dimensional complexity from two-dimensional precursors, bridging arene feedstocks with alicyclic structures. When those processes are applied to pyridines, quinolines, and isoquinolines, partially or fully saturated nitrogen heterocycles are formed, which are among the most significant structural components of pharmaceuticals and natural products. The inherent challenge of those transformations lies in the low reactivity of heteroaromatic substrates, which makes the dearomatization process thermodynamically unfavorable. Usually, connecting the dearomatization event to the irreversible formation of a strong C−C, C− H, or C−heteroatom bond compensates the energy required to disrupt the aromaticity. This aromaticity breakup normally results in a 1,2-or 1,4-functionalization of the heterocycle. Moreover, the combination of these dearomatization processes with subsequent transformations in tandem or stepwise protocols allows for multiple heterocycle functionalizations, giving access to complex molecular skeletons. The aim of this review, which covers the period from 2016 to 2022, is to update the state of the art of nucleophilic dearomatizations of pyridines, quinolines, and isoquinolines, showing the extraordinary ability of the dearomative methodology in organic synthesis and indicating their limitations and future trends.

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Section: Applications To Natural Product Synthesismentioning

confidence: 99%

Recent Strategies in the Nucleophilic Dearomatization of Pyridines, Quinolines, and Isoquinolines

Escolano,

Gaviña,

Alzuet-Piña

et al. 2024

Chem. Rev.

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“…In 2022, Harmata et al reported the comparatively short synthesis of the ABC-tricyclic building block 145 for daphnicyclidin A (Scheme 14). [29] An intramolecular (4 + 3) cycloaddition of the 3-hydroxypyridinium cation 144 at high temperature on a preparative scale enabled a rapid build-up of the required molecular complexity. The convergent synthesis of the hydroxypyridinium cation 144 was accomplished by N-alkylation of ethyl 5-hydroxynicotinate 143 with the tosylate 142.…”

Section: Synthetic Effortsmentioning

confidence: 99%

Daphnicyclidin Alkaloids 2001–2023

Gierok,

Hiersemann

2024

Eur J Org Chem

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The Daphniphyllum alkaloids represent a particularly diverse class of complex diterpene alkaloids, which are characterized by their enormous structural diversity. The daphnicyclidins, a subgroup of these alkaloids, stand out due to their unique pentafulvene structural motif. This review article gives an overview of the compounds that have been isolated so far and can be assigned to this subgroup. Furthermore, all synthesis approaches and total syntheses published to date are presented.

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“… 5 Also noteworthy are the total syntheses of several Daphniphyllum alkaloids recently reported by Li. 9 Moreover, only a few studies have reported synthetic strategies toward compounds embodying tricyclic scaffolds (ABC rings) 6 as potential advanced precursors of the target alkaloids.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of the ABC Core of Daphniphyllum Alkaloids with a [5–6–7] Azatricyclic Scaffold via Ring Expansion of Azabicyclic and Azatricyclic Building Blocks

Marquès,

González-Lizana,

Diaba

et al. 2024

J. Org. Chem.

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The [5–6–7] azatricyclic ABC core, found in several Daphniphyllum alkaloids, has been synthesized through a novel route involving ring expansion of a perhydroindolone to afford the AC ring system and a radical B ring closure as key steps. The level of functionalization of the reported octahydro-1,7-ethanocyclohepta[b]pyrroles suggests that they can serve as valuable building blocks in this alkaloid field. Also reported is the first synthesis of homomorphans by the ring enlargement of 2-azabicyclo[3.3.1]nonanes.

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Intramolecular (4+3) Cycloadditions of Oxidopyridinium Ions: Towards Daphnicyclidin A

Cited by 8 publications

References 35 publications

Recent Strategies in the Nucleophilic Dearomatization of Pyridines, Quinolines, and Isoquinolines

Recent Strategies in the Nucleophilic Dearomatization of Pyridines, Quinolines, and Isoquinolines

Daphnicyclidin Alkaloids 2001–2023

Synthesis of the ABC Core of Daphniphyllum Alkaloids with a [5–6–7] Azatricyclic Scaffold via Ring Expansion of Azabicyclic and Azatricyclic Building Blocks

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