Application of ring-rearrangement metathesis in organic synthesis: A grand design

Kotha, Sambasivarao; Meshram, Milind; Aswar, Vikas R.

doi:10.1016/j.tetlet.2019.151337

Cited by 19 publications

(7 citation statements)

References 62 publications

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“…In view of our continued interest in developing new synthetic strategies, we identified the RRM as a key step and envisioned a modular strategy that can produce a wide range of diverse polyquinanes. In this regard, a less explored exo -dicyclopentadiene-1-one ( 8 ) is identified as a suitable precursor for the RRM route.…”

Section: Introductionmentioning

confidence: 92%

A Modular Approach to Angularly Fused Polyquinanes via Ring-Rearrangement Metathesis: Synthetic Access to Cameroonanol Analogues and the Basic Core of Subergorgic Acid and Crinipellin

Kotha

Keesari

2021

J. Org. Chem.

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We describe a modular approach to angularly fused polyquinanes that are core units of many natural products such as cameroonanol, subergorgic acid, and crinepellin, etc. in excellent yields by employing atom-economic ring-rearrangement metathesis as a key step. Our work highlights, the synthesis of cameroonanol analogues 1–6 and their ester derivatives by using the stereoselective reduction of the carbonyl group by using DIBAL-H- and DCC-mediated coupling as the key reactions. The subergorgic acid core 7 was produced by LDA-mediated kinetically controlled regio- and stereoselective ring-junction allylation as a critical step. Moreover, it is worth mentioning that the present strategy relies on a less explored exo-dicyclopentadiene-1-one (8) and produces highly congested polycyclic frameworks containing up to seven contiguous stereogenic centers including quaternary carbons up to two. All of the new molecules were characterized by NMR data. The structure and relative stereochemistry of some compounds were confirmed by chemical methods and further supported by single-crystal X-ray diffraction studies. The newly reported tri- and tetraquinane skeletons are present in many naturally occurring bioactive polyquinanes. Hence, this strategy is useful for designing various “druglike molecules” and expands the chemical space of cyclopentanoids that are useful in medicinal chemistry.

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Section: Introductionmentioning

confidence: 92%

A Modular Approach to Angularly Fused Polyquinanes via Ring-Rearrangement Metathesis: Synthetic Access to Cameroonanol Analogues and the Basic Core of Subergorgic Acid and Crinipellin

Kotha

Keesari

2021

J. Org. Chem.

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“…Thecatalytically active species is then formed when the bulky alkylidene or carbene reacts with asubstrate alkene.Such processes are sluggish if the starting alkene is hindered. Ac ase in point is the ROCM/RCM reaction that converts diene 18 to cyclic ether 19 [11] (Scheme 4a). Association of neophylidene Mo-1 with the strained and more reactive norbornyl alkene in 18 (exo face) would engender considerable steric pressure,a nd, consequently,n o product was formed after one day.Onthe other hand, in the presence of 10 mol %d iallyl ether,aconvenient and easily quantifiable ethylene surrogate, [12] the more exposed Mo-1meth-1 a was rapidly formed, culminating in enantioselective formation of alkylidene 20,w hich can undergo RCM to furnish 19 in 54 %y ield and 96:4 e.r.…”

Section: Fori Mproving Efficiencymentioning

confidence: 99%

Impact of Ethylene on Efficiency and Stereocontrol in Olefin Metathesis: When to Add It, When to Remove It, and When to Avoid It

et al. 2020

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Ethylene is the byproduct of olefin metathesis reactions that involve one or more terminal alkenes. Its volatility is one reason why many cross‐metathesis or ring‐closing metathesis processes, which are reversible transformations, are efficient. However, because ethylene can be converted to a methylidene complex, which is a highly reactive but relatively unstable species, its concentration can impact olefin metathesis in other ways. In some cases, introducing excess ethylene can increase reaction rate owing to faster catalyst initiation. Ethylene and a derived methylidene complex can also advantageously inhibit substrate or product homocoupling, and/or divert a less selective pathway. In other instances, a methylidene's low stability and high activity may lead to erosion of efficiency and/or kinetic selectivity, making it preferable that ethylene is removed while being generated. If methylidene decomposition is so fast that there is little or no product formation, it is best that ethylene and methylidene complex formation is avoided altogether. This is accomplished by the use of di‐ or trisubstituted alkenes in stereoretentive processes, which includes adopting methylene capping strategy. Here, we analyze the different scenarios through which ethylene and the involvement of methylidene complexes can be manipulated and managed so that an olefin metathesis reaction may occur more efficiently and/or more stereoselectively.

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“…In view of our continuous efforts in assembling various architecturally intricate molecules, [18] we aimed to synthesize molecules with cis-cis-cis stereochemistry by adapting a simple and efficient strategy that involves a substrate-driven regioand stereoselective epoxidation [17a] followed by RRM as key steps starting with endo-enone 16. To this end, we report the synthesis of both a fused 5/5/6-tricyclic enone 18 and a fused 5/5/6-tricyclic-α,β-epoxyketone 27 (Figure 4e).…”

Section: Introductionmentioning

confidence: 99%

Synthesis of 1,3‐cis‐Fused Tricyclic System through Regio‐ and Stereoselective Epoxidation and Ring‐Rearrangement Metathesis: Access To Basic Core of Presilphiperfolanols

2023

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Here, we report a new synthetic approach to a highly strained 1,3-fused cis-cis-cis-5/5/6 tricyclic system that appeared among the presilphiperfolanol analogues. The cis-fusion of six-membered ring to a diquinane moiety is accomplished by substratecontrolled regio-and stereoselective epoxidation, and ringrearrangement metathesis (RRM) sequence. In this regard, both early-, and late-stage epoxidation and RRM reactions were studied. The target compound, cis-cis-cis-5/5/6 tricyclic ketone with an α,β-oxirane ring can serve as a key building block to produce various presilphiperfolanol analogues. The cis-cis-cis-5/ 5/6-tricyclic-α,β-epoxyketone can also act as masked enone and therefore useful for various chemical transformations in organic synthesis. The short synthetic sequence disclosed here may be useful to design various biologically important molecules. The newly reported molecules are well-characterized by NMR, HRMS, and IR spectral data.

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Application of ring-rearrangement metathesis in organic synthesis: A grand design

Cited by 19 publications

References 62 publications

A Modular Approach to Angularly Fused Polyquinanes via Ring-Rearrangement Metathesis: Synthetic Access to Cameroonanol Analogues and the Basic Core of Subergorgic Acid and Crinipellin

A Modular Approach to Angularly Fused Polyquinanes via Ring-Rearrangement Metathesis: Synthetic Access to Cameroonanol Analogues and the Basic Core of Subergorgic Acid and Crinipellin

Impact of Ethylene on Efficiency and Stereocontrol in Olefin Metathesis: When to Add It, When to Remove It, and When to Avoid It

Synthesis of 1,3‐cis‐Fused Tricyclic System through Regio‐ and Stereoselective Epoxidation and Ring‐Rearrangement Metathesis: Access To Basic Core of Presilphiperfolanols

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