Catalyst-free Tandem 1,3-Dipolar Cycloaddition/Aldol Condensation: Diastereoselective Construction of the Azatetraquinane Skeleton

Abstract

The one-pot regioselective and diastereoselective method for the synthesis of 5-(het)­aroyl-7-(het)­arylhexahydrobenzo­[4,5]­pentaleno­[1,6a-b]­(thia)­pyrrolizine-6,12-diones from accessible 1,5-di­(het)­arylpent-4-ene-1,3-diones or curcuminoids in 38–98% yield was developed. This reaction proceeds as a sequence of 1,3-dipolar cycloaddition of azomethine ylide generated in situ from ninhydrin and (thia)­proline at the CC bond of corresponding enedione, followed by spontaneous intramolecular aldol condensation and leads to the formation of an azatetraquinane scaffold.

Design and synthesis of spirooxindole–pyrrolidines embedded with indole and pyridine heterocycles by multicomponent reaction: anticancer and in silico studies

“…In endo -TS-2, the ylide attacks the dipolarophile from the side of a bulkier indole moiety, and the activation energy of such a process is higher. 17 The reaction occurs through one of the ylide geometries; therefore, its addition to dipolarophiles takes place under the control of relative stereochemistry at the spiro center. The formation of sterically hindered ylide was not obtained owing to steric repulsion between the carbonyl group of oxindole and the methyl group of sarcosine.…”

Hemicurcuminoids (1-styryl-1,3-diketones) – valuable multi-faceted building blocks for organic synthesis

“…It is worthy of a separate mention that due to the presence of two additional carbonyl groups in the ninhydrin molecule, spiroadducts A derived from it undergo an intramolecular aldol condensation with the methylene group of the dicarbonyl moiety, giving azatetraquinanes 120 as individual diastereomers (Scheme 70). 135 While spiroadducts 123 obtained from acenaphthenequinone could not participate in the same condensation as A, their phenylglycine-based analogs 124 were successfully acetylated by acetyl chloride without participation of any base to give spirocycloamides 125 (Scheme 71). 134…”

“…It is worthy of a separate mention that due to the presence of two additional carbonyl groups in the ninhydrin molecule, spiroadducts A derived from it undergo an intramolecular aldol condensation with the methylene group of the dicarbonyl moiety, giving azatetraquinanes 120 as individual diastereomers (Scheme 70). 135…”

A Molecular Iodine-Mediated Synthesis of Cyclopenta[c]furo[3,2-b]furan-5,6-diones: Assembly of an Angular Dioxatriquinane Core

“…Recently, Zimnitskiy and co-workers 15 synthesized a number of azatetraquinane systems based on 1,3-dipolar cycloaddition of stabilized azomethine ylides and 1,5-di(het)arylpent-4-ene-1,3-diones (Scheme 1a). In our previous work, we synthesized a number of functionalized indenopyrrolizines with an angular azatriquinane skeleton using a sequence of 1,3-dipolar cycloaddition and nucleophilic addition reactions involving two molecules of dialkyl acetylenedicarboxylates and the corresponding ylides (Scheme 1b).…”