Macrocyclic enol-ethers containing an acetylenic group from the red alga Phacelocarpus labillardieri

1982 ◽  
Vol 35 (1) ◽  
pp. 113 ◽  
Author(s):  
R Kazlauskas ◽  
PT Murphy ◽  
RJ Wells ◽  
AJ Blackman
Keyword(s):  
Red Alga ◽  
Enol Ether ◽  
Enol Ethers ◽  
Acetylenic Group

Four new acetate-derived metabolites have been isolated from two collections of the red alga Phacelocarpus labillardieri. Three of these metabolites were 2,6-disubstituted pyran-4-ones containing a macrocyclic enol-ether ring. The fourth compound was a 6-substituted pyran-2-one derivative.

Carbon-carbon bond formation in reactions of PhIO.cntdot.HBF4-silyl enol ether adduct with alkenes or silyl enol ethers

1989 ◽  
Vol 54 (11) ◽  
pp. 2605-2608 ◽  
Author(s):  
V. V. Zhdankin ◽  
M. Mullikin ◽  
Rik Tykwinski ◽  
Bruce Berglund ◽  
Ronald Caple ◽  
...  
Keyword(s):  
Bond Formation ◽  
Enol Ether ◽  
Enol Ethers ◽  
Carbon Bond ◽  
Silyl Enol Ethers ◽  
Carbon Carbon Bond ◽  
Silyl Enol Ether

scholarly journals Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

2010 ◽  
Vol 6 ◽  
Author(s):  
Fabian Pfrengle ◽  
Hans-Ulrich Reissig
Keyword(s):  
Lewis Acid ◽  
Functional Group ◽  
Tricarboxylic Acid ◽  
Membered Ring ◽  
Enol Ether ◽  
Enol Ethers ◽  
Acidic Conditions ◽  
Hydroxylamine Derivatives

A stereodivergent synthesis of enantiopure 3,6-dihydro-2H-pyrans is presented. The addition of lithiated enol ethers to carbohydrate-derived nitrones afforded syn- or anti-configured hydroxylamine derivatives 4a–d that were cyclized under Lewis acidic conditions to yield functionalized dihydropyrans cis- or trans-5a–d containing an enol ether moiety. This functional group was employed for a variety of subsequent reactions such as dihydroxylation or bromination. Bicyclic enol ether 19 was oxidatively cleaved to provide the highly functionalized ten-membered ring lactone 20. The synthesized enantiopure aminopyrans 24, 26, 28 and 30 can be regarded as carbohydrate mimetics. Trimeric versions of 24 and 28 were constructed via their attachment to a tricarboxylic acid core.

An Access to Highly Enantioenriched cis-3,5-Disubstituted γ-Lactones from α-Bromoacetate and Silyl Enol Ether

2021 ◽  
Author(s):  
Ha Rim Lee ◽  
Seo Yun Kim ◽  
Min Ji Park ◽  
Yong Sun Park
Keyword(s):  
Nucleophilic Substitution ◽  
Enol Ether ◽  
Enol Ethers ◽  
Silyl Enol Ethers ◽  
Synthetic Strategy ◽  
Silyl Enol Ether

A novel synthetic strategy for highly enantioenriched cis-3,5-disubstituted γ-lactones has been developed by the AgOTf-promoted nucleophilic substitution of α-bromoacetates with silyl enol ethers and subsequent reductive lactonization. The utility of...

Eistert's Methyl Enol Ethers of Acetylacetone

1971 ◽  
Vol 49 (16) ◽  
pp. 2672-2675 ◽  
Author(s):  
Dennis V. C. Awang
Keyword(s):  
Carbonyl Oxygen ◽  
Enol Ether ◽  
Trans Conformation ◽  
Enol Ethers ◽  
Solvent Shift ◽  
Acid Catalyzed ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects ◽  
Configuration And Conformation ◽  
Shift Data

The configuration and conformation of the two isomeric methyl enol ethers of acetylacetone (1) have been unequivocally demonstrated. The n.m.r. solvent shift data and observation of nuclear Overhauser effects support an s-cis conformation for the more stable isomer 2 bearing acetyl trans to methoxyl while indicating an s-trans conformation for the less stable enol ether 3 having acetyl cis to methoxyl. The facile acid-catalyzed isomerization of 3 to 2 apparently proceeds by reversible protonation of carbonyl oxygen since no deuterium incorporation is observed when the isomerization is performed in acetic acid-d4.

The Synthesis of Trisubstituted Enol Ethers and of Methyl Ketones from Ketones

1973 ◽  
Vol 51 (6) ◽  
pp. 981-983 ◽  
Author(s):  
Gilles Caron ◽  
Jean Lessard
Keyword(s):  
Acid Hydrolysis ◽  
Hydroxy Acid ◽  
Reliable Method ◽  
Acid Salt ◽  
Methyl Ketones ◽  
Enol Ether ◽  
Mild Acid Hydrolysis ◽  
Enol Ethers ◽  
Hydrolysis Of ◽  
Mild Acid

A reliable method for the synthesis of trisubstituted enol ethers (and of the corresponding methyl ketones) is described involving the condensation of the α-lithiated 2-methoxypropionic acid salt with a ketone to give a β-hydroxy acid, the cyclization to a β-lactone which is then decarboxylated (and mild acid hydrolysis of the enol ether).

scholarly journals α-Tertiary Dialkyl Ether Synthesis via Reductive Photocatalytic α-Functionalization of Alkyl Enol Ethers

2020 ◽  
Author(s):  
Jamie Leitch ◽  
Thomas Rossolini ◽  
Tatiana Rogova ◽  
Darren J. Dixon
Keyword(s):  
Single Electron Transfer ◽  
Enol Ether ◽  
Enol Ethers ◽  
Ion Generation ◽  
Wide Range ◽  
Oxocarbenium Ion ◽  
Alkyl Enol Ethers ◽  
Ether Synthesis ◽  
Dialkyl Ethers ◽  
Led Irradiation

The photocatalytic construction of C(sp<sup>3</sup>)-rich α-tertiary dialkyl ethers through the reductive α-functionalization of alkyl enol ether substrates with conjugated alkenes in the presence of a Hantzsch ester terminal reductant under blue LED irradiation, is described. Pivoting on oxocarbenium ion generation <i>via</i> an initial TMSCl-facilitated protic activation of the enol ether substrate, subsequent single electron transfer delivers the key nucleophilic α-oxy tertiary radical capable of productively combining with a variety of alkene substrates. The new reductive functionalization strategy was simple to perform, efficient, broad in scope with respect to both alkene acceptor and enol ether donor fragments and delivered a wide range of complex α-tertiary dialkyl ether architectures.

scholarly journals Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

2018 ◽  
Vol 14 ◽  
pp. 992-997 ◽  
Author(s):  
Keshaba N Parida ◽  
Gulab K Pathe ◽  
Shimon Maksymenko ◽  
Alex M Szpilman
Keyword(s):  
Organic Synthesis ◽  
Cross Coupling ◽  
Enol Ether ◽  
Enol Ethers ◽  
Ketone Enolates ◽  
The Cross

Due to their closely matched reactivity, the coupling of two dissimilar ketone enolates to form a 1,4-diketone remains a challenge in organic synthesis. We herein report that umpolung of a ketone trimethylsilyl enol ether (1 equiv) to form a discrete enolonium species, followed by addition of as little as 1.2–1.4 equivalents of a second trimethylsilyl enol ether, provides an attractive solution to this problem. A wide array of enolates may be used to form the 1,4-diketone products in 38 to 74% yield. Due to the use of two TMS enol ethers as precursors, an optimization of the cross-coupling should include investigating the order of addition.

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