Allenic Natural Products and Pharmaceuticals

Krause, Norbert; Hoffmann‐Röder, Anja

doi:10.1002/9783527619573.ch18

Cited by 34 publications

(14 citation statements)

References 249 publications

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“…We envisaged that homopropargylic alcohols can offer a gateway towards α‐allenyl ketones and alcohols, which are highly prevalent scaffolds in carotinoids and terpenoids natural products (e.g. Mimulaxanthin or Icariside B 1 ) [27] . Indeed, straightforward oxidation‐isomerization sequence delivered the allene 47 in high yield, thus testifying the feasibility of our protocol towards its utilization in synthetic endeavors.…”

Section: Resultsmentioning

confidence: 88%

“…Both acyclic( 23)a nd cyclic (24)(25)a liphatic aldehydes afforded the desired product in moderate to excellent yields (62-94 %), even in the presence of alkenes (25). Pleasingly, electron-rich aromatics such as indole (26)a nd furan (27) were tolerated, despite in the latter case the lability of the heterocyclic system deemed responsible for the reduced yield (39 %). An array of 3-phenylpropanal derivatives (28)(29)(30)(31) bearing both electron-donating (28,29)and -withdrawing (30,31)groups at different positions of the aromatic ring delivered the product in good to excellent yields (77-93 %).…”

Section: Angewandte Chemiementioning

confidence: 99%

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Radical Carbonyl Propargylation by Dual Catalysis

2020

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Carbonyl propargylation has been established as a valuable tool in the realm of carbon–carbon bond forming reactions. The 1,3‐enyne moiety has been recognized as an alternative pronucleophile in the above transformation through an ionic mechanism. Herein, we report for the first time, the radical carbonyl propargylation through dual chromium/photoredox catalysis. A library of valuable homopropargylic alcohols bearing all‐carbon quaternary centers could be obtained by a catalytic radical three‐component coupling of 1,3‐enynes, aldehydes and suitable radical precursors (41 examples). This redox‐neutral multi‐component reaction occurs under very mild conditions and shows high functional group tolerance. Remarkably, bench‐stable, non‐toxic, and inexpensive CrCl3 could be employed as a chromium source. Preliminary mechanistic investigations suggest a radical‐polar crossover mechanism, which offers a complementary and novel approach towards the preparation of valuable synthetic architectures from simple chemicals.

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Section: Resultsmentioning

confidence: 88%

Section: Angewandte Chemiementioning

confidence: 99%

Radical Carbonyl Propargylation by Dual Catalysis

2020

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“…31 Notably, enantioenriched allenes have many potential applications. 32 In asymmetric catalysis, the transformations of propargyl vinyl ethers to provide β-substituted allenyl carbonyls remains highly challenging, as evidenced by the fact that no catalytic asymmetric Saucy-Marbet Claisen rearrangements were reported prior the our effort. 18,33 Examination of simple models revealed that the alkyne sp centers significantly perturb the sigmatropic rearrangement transition state.…”

Section: Resultsmentioning

confidence: 99%

Copper(II)- and Palladium(II)-Catalyzed Enantioselective Claisen Rearrangement of Allyloxy- and Propargyloxy-Indoles to Quaternary Oxindoles and Spirocyclic Lactones

et al. 2012

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In this paper, a strategy to obtain highly enantioselective catalysts for the Claisen rearrangement of allyloxy- and propargyloxy-indoles is outlined. Ultimately, copper BOX and palladium BINAP or PHOX catalysts were discovered as superior in catalyzing Claisen rearrangements of allyloxy- or proparyloxy-substituted indoles to generate oxindoles bearing allyl- or allenyl-substituted quaternary centers. This method proved to be tolerant of a broad range of functional groups. Tandem reactions of the silyl-allene products provide rapid access to a variety of spirocyclic oxindoles in one operation.

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“…Furthermore, the number of bisallenic natural products that have been described so far is very small. In this area one can assume that more discoveries will be made once a directed search is initiated [308]. The occasional use of bisallenes in polymer chemistry has been pointed out in this review (see Section 4.1).…”

Section: Resultsmentioning

confidence: 99%

The chemistry of bisallenes

Hopf¹,

Μαρκόπουλος²

2012

Beilstein J. Org. Chem.

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SummaryThis review describes the preparation, structural properties and the use of bisallenes in organic synthesis for the first time. All classes of compounds containing at least two allene moieties are considered, starting from simple conjugated bisallenes and ending with allenes in which the two cumulenic units are connected by complex polycyclic ring systems, heteroatoms and/or heteroatom-containing tethers. Preparatively the bisallenes are especially useful in isomerization and cycloaddition reactions of all kinds leading to the respective target molecules with high atom economy and often in high yield. Bisallenes are hence substrates for generating molecular complexity in a small number of steps (high step economy).

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Allenic Natural Products and Pharmaceuticals

Cited by 34 publications

References 249 publications

Radical Carbonyl Propargylation by Dual Catalysis

Radical Carbonyl Propargylation by Dual Catalysis

Copper(II)- and Palladium(II)-Catalyzed Enantioselective Claisen Rearrangement of Allyloxy- and Propargyloxy-Indoles to Quaternary Oxindoles and Spirocyclic Lactones

The chemistry of bisallenes

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