Transformation of substituted 2H-pyran-5-carboxylates into 3R*-vinyl-1,2R*-cyclopropanedicarboxylates

Moorhoff, Cornelis M.; Winkler, D. E.

doi:10.1039/a804237c

Cited by 7 publications

(5 citation statements)

References 32 publications

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“…The preference for the formation of the thermodynamically favored trans cyclopropanes is attributed to the steric bulk of the enolate being directed away from the cyclic 1-2λ 5 -oxaphospholane moiety as depicted in 30a . Similar stereochemical outcomes during cyclopropane formation from enolates have been cited and , Scheme .…”

Section: Discussionsupporting

confidence: 62%

A New Route to Diastereomerically Pure Cyclopropanes Utilizing Stabilized Phosphorus Ylides and γ-Hydroxy Enones Derived from 1,2-Dioxines: Mechanistic Investigations and Scope of Reaction

2000

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A new chemical transformation for the construction of diversely functionalized cyclopropanes utilizing 1,2-dioxines and stabilized phosphorus ylides as the key precursors is presented. Through a series of mechanistic studies we have elucidated a clear understanding of the hitherto unknown complex relationship between 1, 2-dioxines 1a-e, and their isomeric cis/trans gamma-hydroxy enones (23 and 21a-e), cis/trans hemiacetals 24a-e, and beta-ketoepoxides (e.g., 26), and how these precursors can be utilized to construct diversely functionalized cyclopropanes. Furthermore, several new synthetically useful routes to these structural isomers are presented. Key features of the cyclopropanation include the ylide acting as a mild base inducing the ring opening of the 1,2-dioxines to their isomeric cis gamma-hydroxy enones 23a-e, followed by Michael addition of the ylide to the cis gamma-hydroxy enones 23a-e and attachment of the electrophilic phosphorus pole of the ylide to the hydroxyl moiety, affording the intermediate 1-2lambda(5)-oxaphospholanes 4 and setting up the observed cis stereochemistry between H1 and H3. Cyclization of the resultant enolate (30a or 30b), expulsion of triphenylphosphine oxide, and proton transfer from the reaction manifold affords the observed cyclopropanes in excellent diastereomeric excess. The utilization of Co(SALEN)(2) in a catalytic manner also allows for a dramatic acceleration of reaction rates when entering the reaction manifold from the 1,2-dioxines. While cyclopropanation is favored by the use of ester-stabilized ylides, the use of keto- or aldo-stabilized ylides results in a preference for 1,4-dicarbonyl formation through a competing Kornblum-De La Mare rearrangement of the intermediate hemiacetals. This finding can be attributed to subtle differences in ylide basicity/nucleophilicity. In addition, the use of doubly substituted ester ylides allows for the incorporation of another stereogenic center within the side chain. Finally, our studies have revealed that the isomeric trans gamma-hydroxy enones and the beta-keto epoxides are not involved in the cyclopropanation process; however, they do represent an alternative entry point into this reaction manifold.

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Section: Discussionsupporting

confidence: 62%

A New Route to Diastereomerically Pure Cyclopropanes Utilizing Stabilized Phosphorus Ylides and γ-Hydroxy Enones Derived from 1,2-Dioxines: Mechanistic Investigations and Scope of Reaction

2000

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“…Since 2 H -pyrans undergo a reversible electrocyclic ring-opening to 1-oxatrienes, classical strategies toward monocyclic 2 H -pyrans generally afford an equilibrating mixture . Typically, the substrate-dependent equilibrium is dominated by 1-oxatrienes, 3d,g while the 2 H -pyran form is favored only in a few cases due to increased steric interactions. , Although there are numerous applications of 1-oxatrienes, , the synthetic utility of monocyclic 2 H -pyrans is somewhat limited. , …”

mentioning

confidence: 99%

Synthesis of Stable 2H-Pyran-5-carboxylates via a Catalyzed Propargyl-Claisen Rearrangement/Oxa-6π Electrocyclization Strategy

Menz

Kirsch

2006

Org. Lett.

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[reaction: see text] The application of easily accessed propargyl vinyl ethers for the synthesis of monocyclic 2H-pyrans was achieved. Under the reaction conditions, highly substituted heterocycles were obtained in moderate to excellent yields. The one-pot sequence proceeds via a Ag(I)-catalyzed propargyl-Claisen rearrangement, followed by a base-catalyzed isomerization, and 6pi-oxaelectrocyclization, leading to the formation of stable 2H-pyrans.

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“…Recently, we described the condensations of arsonium ylides and 2H-pyran-5-carboxylates 1. 3,4,5,6 2H-pyran-5-carboxylates 1 7 have the unique ability to undergo reversible electrocyclic ring opening to the ketodiene 2 8 making these compounds available for Michael attack. For example, methyl 3-oxo-4-(triphenylarsoranylidene)butanoate 3 reacted with 2H-pyran-5-carboxylates 1 and gave mainly cyclohexenonedicarboxylates 4 and tetrahydrobenzofurandicarboxylates 5 (R 2 = H) as a minor byproduct 4 (Scheme I).…”

Section: Introductionmentioning

confidence: 99%

New Annulation Techniques; Condensations of Phosphonium Ylides and Substituted 2H‐Pyran‐5‐carboxylates; Preparation of Cyclohexenonedicarboxylates and Cyclohexadienedicarboxylates

Moorhoff

2003

J Chinese Chemical Soc

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Substituted alkyl 2H-pyran-5-carboxylates condensed with alkyl 3-oxo-4-(triphenylphosphoranylidene)butanoate and alkyl 4-(triphenylphosphoranylidene)-2-butenoate to form substituted 2-vinyl-6-oxo-4cyclohexene-1,3-dicarboxylates, some of which showed ecto-parasiticidal activity in pets and cattle, and substituted 2-vinyl-3,5-cyclohexadiene-1,3-dicarboxylates, respectively. The last mentioned product is in marked contrast to the product obtained using the corresponding arsonium analogue.

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Transformation of substituted 2H-pyran-5-carboxylates into 3R-vinyl-1,2R-cyclopropanedicarboxylates

Cited by 7 publications

References 32 publications

A New Route to Diastereomerically Pure Cyclopropanes Utilizing Stabilized Phosphorus Ylides and γ-Hydroxy Enones Derived from 1,2-Dioxines: Mechanistic Investigations and Scope of Reaction

A New Route to Diastereomerically Pure Cyclopropanes Utilizing Stabilized Phosphorus Ylides and γ-Hydroxy Enones Derived from 1,2-Dioxines: Mechanistic Investigations and Scope of Reaction

Synthesis of Stable 2H-Pyran-5-carboxylates via a Catalyzed Propargyl-Claisen Rearrangement/Oxa-6π Electrocyclization Strategy

New Annulation Techniques; Condensations of Phosphonium Ylides and Substituted 2H‐Pyran‐5‐carboxylates; Preparation of Cyclohexenonedicarboxylates and Cyclohexadienedicarboxylates

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