Lewis acid-catalyzed [3 + 2] annulations of oxindole based spirocyclic donor-acceptor cyclopropanes with ynamides.
03 Nov 2021-Organic and Biomolecular Chemistry (The Royal Society of Chemistry)-Vol. 19, Iss: 44, pp 9645-9648
TL;DR: In this paper, annulations of oxindole based spirocyclic donor-acceptor cyclopropanes and ynamides catalyzed by copper triflate have been developed for the synthesis of biologically important spirocyclopenteneoxindoles.
Abstract: [3 + 2] annulations of oxindole based spirocyclic donor–acceptor cyclopropanes and ynamides catalyzed by copper triflate have been developed for the synthesis of biologically important spirocyclopenteneoxindoles. These reactions tolerated a wide scope of substrates and provided the desired products in good to high yields (up to 90%) with up to >40 : 1 diastereoselectivities under mild conditions.
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TL;DR: In this article , a multigram synthesis of 4-(dimethylamino)pyridinium azide, a stable, nonexplosive, low-hygroscopic source of azide ion soluble in both protic and aprotic organic solvents, was reported.
Abstract: We report a procedure for the multigram synthesis of 4-(dimethylamino)pyridinium azide, a stable, non-explosive, low-hygroscopic source of azide ion soluble in both protic and aprotic organic solvents. In protic ionic liquid media this reagent was shown to serve as a safer equivalent of toxic and unstable hydrazoic acid. The synthetic utility of this system was demonstrated using donor-acceptor cyclopropane ring opening as a model process. General procedures furnishing a variety of dialkyl (2-azido-2-arylethyl)malonates or 4-azido-4-arylbutyrates, depending on the protic ionic liquid applied, were elaborated. The conversion times for studied donor-acceptor cyclopropanes were established providing the relative reactivity sequence. The application of 4-(dimethylamino)pyridinium azide for a conventional nucleophilic substitution, oxirane ring opening, (3+2)-cycloaddition to (thio)cyano group as well as their combinations realized as telescopic synthesis was also demonstrated.
3 citations
TL;DR: In this paper , an organocatalytic cascade approach for the synthesis of spiro-cyclopropyl oxindole derivatives has been developed based on asymmetric vinylogous Michael addition of 4-nitroisoxazole derivatives to N-Boc isatylidene malonates followed by intramolecular alkylation.
Abstract: A novel organocatalytic cascade approach for the synthesis of spiro-cyclopropyl oxindole derivatives has been developed. The methodology is based on asymmetric vinylogous Michael addition of 4-nitroisoxazole derivatives to N-Boc isatylidene malonates followed by intramolecular alkylation. Its remarkable stereocontrol, wide substrate scope, and scalability highlight this new developed strategy. Moreover, this work represents the first example of vinylogous Michael initiated ring closure (MIRC) reaction for the synthesis of chiral 3,3'-cyclopropyl oxindole.
1 citations
TL;DR: A series of 1,6-diketone derivatives were prepared by first copper (II) trifluoromethanesulfonate catalysed ring-opening of cyclopropyl ketones with 1,3Diketones followed by DBU-promoted retro-Claisen-type reactions as mentioned in this paper .
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TL;DR: Asymmetric ring-opening reactions of donor-acceptor cyclopropanes with 1,3-cyclodiones have been established for the synthesis of enantioenriched γ-hydroxybutyric acid derivatives in the presence of Cu(ii)/trisoxazoline catalyst as mentioned in this paper .
Abstract: Asymmetric ring-opening reactions of donor–acceptor cyclopropanes with 1,3-cyclodiones have been established for the synthesis of enantioenriched γ-hydroxybutyric acid derivatives in the presence of Cu(ii)/trisoxazoline catalyst. These reactions offered the desired products in 70% to 93% yields with 79% to 99% enantiomeric excesses.
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1,273 citations
TL;DR: This Review highlights the appropriate tools for successfully employing donor-acceptor cyclopropanes in ring-opening reactions, cycloadditions, and rearrangements.
Abstract: The effective use of ring strain has been applied to considerable advantage for the construction of complex systems. The focus here is directed towards cyclopropanes as building blocks for organic synthesis. Although thermodynamics should take the side of synthetic chemists, only a specific substitution pattern at the cyclopropane ring allows for particularly mild, efficient, and selective transformations. The required decrease in the activation barrier is achieved by the combined effects of vicinal electron-donating and electron-accepting moieties. This Review highlights the appropriate tools for successfully employing donor–acceptor cyclopropanes in ring-opening reactions, cycloadditions, and rearrangements.
805 citations
TL;DR: This review focuses on the enantioselective synthesis of spirooxindoles via organocascade strategies and is organized on the basis of three primary starting materials and then further subdivided according to the types of organocatalyst.
Abstract: Spirooxindoles have become a privileged skeleton given their broad and promising activities in various therapeutic areas. The strategies and catalyst systems described here highlight recent advances in the enantioselective synthesis of spirooxindoles via organocascade strategies. Various organocatalysts with distinct activation modes have found application in constructing these sophisticated compounds. This review focuses on the enantioselective synthesis of spirooxindoles via organocascade strategies and is organized on the basis of three primary starting materials and then further subdivided according to the types of organocatalyst. These methods are of importance for the synthesis of complex natural products and the design of new pharmaceutical compounds. We believe that compounds based on spirooxindole skeletons have the potential to provide novel therapeutic agents and useful biological tools.
677 citations
TL;DR: Ynamides have emerged as powerful synthons for nitrogen-containing heterocycles and nitrogen-substituted rings, and it is hoped this Account will promote continued interest in the chemistry of ynamides.
Abstract: The ynamide functional group activates carbon–carbontriple bonds through an attached nitrogen atom that bears an electron-withdrawing group. As a result, the alkyne has both electrophilic and nucleophilic properties. Through the selection of the electron-withdrawing group attached to nitrogen, chemists can modulate the electronic properties and reactivity of ynamides, making these groups versatile synthetic building blocks. The reactions of ynamides also lead directly to nitrogen-containing products, which provides access to important structural motifs found in natural products and molecules of medicinal interest. Therefore, researchers have invested increasing time and research in the chemistry of ynamides in recent years.This Account surveys and assesses new organic transforma-tions involving ynamides developed in our laboratory and in others around the world. We showcase the synthetic power of ynamides for rapid assembly of complex molecular structures. Among the recent reports of ynamide transformatio...
444 citations
TL;DR: A newly designed organocatalytic asymmetric domino Michael-aldol reaction between 3-substituted oxindoles and methyleneindolinones that affords complex bispirooxindoles derivatives should be useful in medicinal chemistry and diversity-oriented syntheses of this intriguing class of compounds.
Abstract: Spirooxindoles are important structural motifs found in an array of bioactive compounds. Here a Michael–aldol domino reaction for the construction of bispirooxindoles is presented, creating four stereocentres, including three quaternary carbon centres. Novel multifunctional organocatalysts have been developed for this transformation.
402 citations