Ynol ethers are highly valuable substrates offering a wide range of reactivity. These highly electron-rich heterosubstitued alkynes can be of great synthetic potential. In this mini-review, the different methods for the synthesis of ynol ethers are first presented, divided in three main approaches involving a β-elimination, a carbene rearrangement and a direct oxidation of an alkyne. Their reactivity is then summarized underlying their synthetic utility. This non-exhaustive review aims at presenting the intrinsic reactivity of these compounds, still underexploited in synthesis.
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http://dx.doi.org/10.2533/chimia.2016.93 | DOI Listing |
J Org Chem
August 2024
Faculty of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
This study developed reactions for the phototriggered generation of reactive ynol ethers using alkoxycyclopropenones. The resulting ynol ethers underwent rearrangement to ketenes, which subsequently participated in cycloaddition with alkynes and the acylation of amines. The alkoxy groups in the ynol ethers significantly influenced on the reactivity toward their rearrangement to ketenes.
View Article and Find Full Text PDFJ Org Chem
March 2023
Organisch Chemisches Institut, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
Enol esters and conjugated enynes are valuable structural motifs for synthetic chemistry and material sciences. Herein, the synthesis of tetra-substituted enol ester 2-iodobenzoate derivatives was achieved in good yields at room temperature through a gold-catalyzed acyloxyalkynylation of sensitive ynol ethers with ethynylbenziodoxolones (EBXs), the latter acting as bifunctional reactants. The conversion is highly regioselective with a broad substrate scope.
View Article and Find Full Text PDFJ Org Chem
December 2022
Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80210, United States.
Alkyne carbopalladation reactions can rapidly generate multiple new C-C bonds; however, regioselectivity is challenging for intermolecular variants. Using ynol ethers, we observe complete regiocontrol of migratory insertion followed by a second migratory insertion with a pendant alkene to turn-over the catalytic cycle. The resulting products are oligosubstituted 1-indenol ethers with defined stereochemistry based on the initial alkene geometry.
View Article and Find Full Text PDFOrg Biomol Chem
November 2022
Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA.
A new class of push-pull-activated alkynes featuring di- and trifluorinated ynol ethers was synthesized. The difluorinated ynol ether exhibited an optimal balance of stability and reactivity, displaying a substantially improved half-life in the presence of aqueous thiols over the previously reported 1-haloalkyne analogs while reacting just as fast in the hydroamination reaction with ,-diethylhydroxylamine. The trifluorinated ynol ether reacted significantly faster, exhibiting a second order rate constant of 0.
View Article and Find Full Text PDFOrg Lett
November 2021
Institute of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology, Av. Països Catalans 16, 43007 Tarragona, Spain.
A broad scope synthesis of cyclobutanones by gold(I)-catalyzed [2 + 2] cycloaddition of ynol ethers with alkenes has been developed. We also found that internal aryl ynol ethers can undergo (4 + 2) cycloaddition reaction with alkenes leading to the corresponding chromanes.
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