Diversification of <i>ortho</i>‐Fused Cycloocta‐2,5‐dien‐1‐one Cores and Eight‐ to Six‐Ring Conversion by σ Bond C−C Cleavage

Eccleshare, Lee; Lozada‐Rodríguez, Leticia; Cooper, Phillippa; Burroughs, Laurence; Ritchie, John; Lewis, William; Woodward, Simon

doi:10.1002/chem.201601970

Cited by 6 publications

(8 citation statements)

References 20 publications

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“…Recent work carried out within our group [12] highlighted how cascade reactions based around an unusual Cannizzaro like 1,5-hydride transfer [13] can be used to rapidly develop complex molecules, such as 1 (Scheme 1b), from commercially available 2-bromoaldehydes. We envisaged using a platinum(II) chloride catalysed, 6-endo-dig cyclisation [8, 11a] to attain a substituted chrysene from ethynylnaphthalene 1.…”

Section: Resultsmentioning

confidence: 99%

“…The cascade procedure [12] affords crude 1,2-dihydronaphthalen-1-ol 7 which could be directly dehydrated using Amberlyst 15 ® to give silylated ethynylnaphalene 8. Subsequent addition of tetrabutylammonium fluoride solution to the reaction mixture followed by a single purification leads directly to ethynylnaphthalene 2 in up to 70% yield in a single synthetic session.…”

Section: Resultsmentioning

confidence: 99%

“…This observation was not unexpected and is in line with our previous work. [12] ArCClC≡CH, warmed to 0 °C; v) Amberlyst 15® and 3 Å molecular sieves at room temperature; vi) TBAF solution (1 M in THF,6.5 mmol).…”

Section: Scheme 2 Telescoped Synthesis Of Ethynylnapthalenementioning

confidence: 99%

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An efficient synthesis of substituted chrysenes

Eccleshare

Selzer

Woodward

2017

Tetrahedron Letters

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Substituted chrysenes have been swiftly synthesised by the 6-endo-dig cyclisation of ethynylnaphthalenes using platinum(II) chloride. Cyclisation precursors were directly prepared from commercially available 2-bromoaldehydes in a telescoped synthetic procedure involving a Cannizzaro triggered cascade and subsequent dehydration and desilylation. This short synthetic procedure allows rapid access to derivatives of biologically active molecules with useful electronic properties.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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An efficient synthesis of substituted chrysenes

Eccleshare

Selzer

Woodward

2017

Tetrahedron Letters

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“…Fission of a proposed eight-membered heterocyclic intermediate produces product ions at m/z 144.04 and 120.04 (structures 11 and 13, respectively). Eight-membered cyclic intermediates have been described in the literature,[21][22][23] particularly in the excited state fragmentation reactions of chalcones 24. Detection of leucoindigo is important because it is the form of indigotin that is soluble in water and readily adsorbs to textiles 3,25.…”

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confidence: 99%

“…The protonated cis isomer, therefore, is considered as the starting point in the fragmentation of m/z 263.08 to m/z 219.09 (Figure7A). Octacyclic intermediates[21][22][23] (structures 3 and 6) are formed from the attack of the hydroxyl group on the carbonyl bond, allowing for decarboxylation to take place subsequently. Highly fused cyclic structures 5 and 8 are formed after proton migration and decarboxylation.…”

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Profiling the Philippine Blue: Liquid chromatography/mass spectrometry‐based metabolomics study on Philippine Indigofera

Molino

Junio

2021

Rapid Comm Mass Spectrometry

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Rationale High‐throughput liquid chromatography/mass spectrometry (LC/MS) analysis presents an interesting platform for natural dyes research. A particular example is the assessment of the dynamic changes in fermentation mixtures of Philippine Indigofera, and in the investigation of commercially available indigo prepared using traditional and optimized methods. Methods Leaves from Indigofera tinctoria and Indigofera suffruticosa were subjected to methanolic extraction and aqueous fermentation for 48 h. Indigo powders prepared following 2‐day and 15‐day fermentation were also subjected to profiling using ultra‐high‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry (UHPLC/QTOF‐MS). MS2 spectra were annotated through a library search in the community‐curated Global Natural Products Social Molecular Networking (GNPS). Spectra with no library hits in GNPS were annotated by analysis of their fragmentation pathways. Results UHPLC/MS‐based detection and fragmentation analysis led to characterization of leucoindigo and the unreported tryptanthrin intermediate, 5a‐hydroxy‐5,5a‐dihydroindolo[2,1‐b]quinazoline‐6,12‐dione, in the fermentation extract of I. tinctoria leaves. Indigo‐associated metabolites were absent in an Indigofera specimen in Laguna Province, which explained why it did not produce blue dye. Locally produced indigo was abundant in indigotin and indirubin, differentiated based on product ions with the corresponding predicted fragmentation pattern. The relative intensity of indigotin, however, decreased with the traditional process of extended fermentation to produce indigo. Conclusions The study is the first to demonstrate simultaneous MS‐based analysis of reaction intermediates, indigotin dye, side products, and catabolites on actively transforming fermentation extracts of I. tinctoria. New results include annotated mass spectra for leucoindigo, and for the unreported 5a‐hydroxy‐5,5a‐dihydroindolo[2,1‐b]quinazoline‐6,12‐dione, which is probably an intermediate in tryptranthrin synthesis. The proposed fragmentation schemes could guide the annotation of analogous compounds in complex mixtures.

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Syntheses of 7‐, 8‐ and 9‐Bromobenzotropolone, Cross‐Couplings of Their Methyl Ethers, and Deprotection to 7‐, 8‐ or 9‐Substituted Benzotropolones

Brückner

Koblischek

2022

Eur J Org Chem

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Unprotected 6,7‐benzotropolone and bromine were known to undergo an electrophilic substitution delivering the 7‐bromo derivative; it was carried on as its methyl ether. O‐Acetyl‐6,7‐benzotropolone added bromine at the C8=C9 bond whereupon an amine‐induced E1cb elimination led to the 8‐brominated benzotropolone acetate; ester cleavage with aqueous acetic acid and etherification with diazomethane delivered the corresponding methyl ether. O‐Methylbenzotropolone was brominated with N‐bromosuccinimide giving the 9‐brominated methyl ether. The mentioned bromobenzotropolone methyl ethers underwent Pd‐catalyzed C−C and C−B couplings. They comprised Suzuki‐Miyaura couplings (with R−BF3K, R=Me, Bu, vinyl, Ph), Negishi couplings (with BuZnCl), Sonogashira couplings (with HC≡C−R, R=SiMe3, CH2OH, Ph, Bu), Mizoroki‐Heck reactions (with methyl acrylate, methyl vinyl ketone, styrene, 3‐buten‐2‐ol), a carbonylative coupling, and Suzuki‐Miyaura borylations (with B2Pin2). Subsequent O‐demethylations with BCl3 succeeded in most cases; they furnished a library of 34 O‐unprotected Br‐free benzotropolones, 31 of which were unknown before.

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Diversification of ortho‐Fused Cycloocta‐2,5‐dien‐1‐one Cores and Eight‐ to Six‐Ring Conversion by σ Bond C−C Cleavage

Cited by 6 publications

References 20 publications

An efficient synthesis of substituted chrysenes

An efficient synthesis of substituted chrysenes

Profiling the Philippine Blue: Liquid chromatography/mass spectrometry‐based metabolomics study on Philippine Indigofera

Syntheses of 7‐, 8‐ and 9‐Bromobenzotropolone, Cross‐Couplings of Their Methyl Ethers, and Deprotection to 7‐, 8‐ or 9‐Substituted Benzotropolones

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