Synthesis Of Cyclic Enol Ethers Research Articles

ChemInform Abstract: Nickel‐Catalyzed Intramolecular C—O Bond Formation: Synthesis of Cyclic Enol Ethers.

AbstractA simple procedure is elaborated for the preparation of cyclic enol ethers by Ni‐catalyzed cyclization of halogenated alcohols.

Nickel-Catalyzed Intramolecular C-O Bond Formation: Synthesis of Cyclic Enol Ethers.

An efficient and exceptionally mild intramolecular nickel-catalyzed carbon-oxygen bond-forming reaction between vinyl halides and primary, secondary, and tertiary alcohols has been achieved. Zinc powder was found to be an essential additive for obtaining high catalyst turnover and yields. This operationally simple method allows direct access to cyclic vinyl ethers in high yields in a single step.

Nickel‐Catalyzed Intramolecular C−O Bond Formation: Synthesis of Cyclic Enol Ethers

AbstractAn efficient and exceptionally mild intramolecular nickel‐catalyzed carbon–oxygen bond‐forming reaction between vinyl halides and primary, secondary, and tertiary alcohols has been achieved. Zinc powder was found to be an essential additive for obtaining high catalyst turnover and yields. This operationally simple method allows direct access to cyclic vinyl ethers in high yields in a single step.

Enantioselective Synthesis of Cyclic Enol Ethers and All‐Carbon Quaternary Stereogenic Centers Through Catalytic Asymmetric Ring‐Closing Metathesis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Olefin metathesis and isomerization: From undesired side reactions to useful synthetic methodology

Conversion of ruthenium carbene complexes to ruthenium hydride complexes by organometallic transformations in situ opens up interesting synthetic perspectives. In this account the use of Grubbs’ catalyst to synthesize pent-4-enals selectively from diallyl- and allyl homoallyl ethers and scope and limitations of a Tandem RCM-isomerization sequence for the synthesis of cyclic enol ethers are discussed.

Palladium mediated cycloisomerization of sugar alkynols: synthesis of cyclic enol-ethers and spiroketals

Functionalized bicyclic enol-ethers and spiroketals are prepared by Pd catalyzed cycloisomerization of 3- C-alkynylfuranosyl derivatives. Cycloisomerization of differently substituted alkyne derivatives revealed a preference for 6- endo-dig cyclization over 5- exo-dig if the substituent is not sufficiently electron withdrawing. The scope of these cycloisomerizations has been further extended by integrating with conjugate addition.

Enantioselective Synthesis of Cyclic Enol Ethers and All-Carbon Quaternary Stereogenic Centers Through Catalytic Asymmetric Ring-Closing Metathesis

The first examples of catalytic asymmetric ring-closing metathesis (ARCM) reactions of enol ethers are reported. To identify the most effective catalysts, various chiral Mo- and Ru-based catalysts were screened. Although chiral Ru catalysts (those that do not bear a phosphine ligand) promote ARCM in some cases, such transformations proceed in <10% ee. In contrast, Mo-based alkylidenes give rise to efficient ARCM and deliver the desired products in the optically enriched form. Thus, Mo-catalyzed enantioselective transformations allow access to various five- and six-membered cyclic enol ethers in up to 94% ee from readily available achiral starting materials. The first examples of catalytic ARCM that lead to the formation of all-carbon quaternary stereogenic centers are also disclosed. Mechanistic models that offer a plausible rationale for the identity of major enantiomers as well as the observed levels of enantioselectivity are provided. Representative examples demonstrate that the enol ether moiety and the unreacted alkene of the ARCM products can be discriminated with excellent site selectivity (>98%).

Synthesis of Cyclic Enol Ethers from Alkenyl‐β‐dicarbonyl Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of cyclic enol ethers from alkenyl-beta-dicarbonyl compounds.

In this work we describe the cyclofunctionalization of eleven differently substituted alkenyl-beta-dicarbonyl compounds, employing three electrophilic reagents, namely, iodine, p-methoxyphenyltellurium trichloride, and phenylselenenyl bromide. The reactions occur through the enolic form of the substrates, to afford the corresponding iodo-, telluro-, or selenocyclic enol ethers. Substrates bearing trisubstituted double bonds failed in reacting with the selenium and tellurium reagents. In general, beta-diketones reacted faster than beta-keto esters with the three studied electrophiles.

Highly regioselective synthesis of cyclic enol silyl ethers using ring-closing metathesis

We developed the first highly regioselective synthesis of cyclic enol ethers from readily accessible acyclic alkenyl ketones or acyclic alkenyl silyl esters using ring-closing metathesis (RCM). The RCM of acyclic enol silyl ethers was examined using Tebbe reagent 5 or Grubbs catalyst 6 or 7 and successfully proceeded using the second generation Grubbs catalyst 7 to afford the corresponding cyclic enol ethers in high yield (up to 99%, two steps from alkenyl kenone). This process can be applied to syntheses of a variety of cyclic enol ethers in a highly regioselective manner.

ChemInform Abstract: Base‐Induced Rearrangement of Dihydropyran Oxides: A Novel Synthesis of Cyclic Enol Ethers with a Hydroxy‐Function in the Allylic Position.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Base-induced rearrangement of dihydropyran oxides: A novel synthesis of cyclic enol ethers with a hydroxy-function in the allylic position

A sequence of ring closing metathesis of allyl-homoallyl ethers, epoxidation of the resulting dihydropyrans, and rearrangement of the dihydropyran oxides with LDA provides convenient access to 2,3-dihydropyrans with a hydroxy group in the 4-position. The products may serve as starting materials for e.g. the Carbon-Ferrier rearrangement.

The Synthesis of Cyclic Enol Ethers via Molybdenum Alkylidene-Catalyzed Ring-Closing Metathesis

An efficient method for the construction of five- and six-membered cyclic vinyl ethers from unsaturated esters using stoichiometric titanium reagents to convert the esters to acyclic olefinic enol ethers which are then transformed to the desired products by catalytic ring-closing olefin metathesis with a molybdenum alkylidene complex is described

A Convenient One-Step Procedure for the Synthesis of Cyclic Enol Ethers. The Preparation of 1-Methoxy-1-cycloalkenes.

A Convenient One-Step Procedure for the Synthesis of Cyclic Enol Ethers. The Preparation of 1-Methoxy-1-cycloalkenes.