Zinc-Catalyzed Enantioselective [3 + 3] Annulation for Synthesis of Chiral Spiro[indoline-3,4'-thiopyrano[2,3-b]indole] Derivatives

With a dinuclear zinc-ProPhenol complex as a catalyst, an efficient and novel [3 + 3] annulation of indoline-2-thiones and isatylidene malononitriles has been successfully developed via the Brønsted base and Lewis acid cooperative activation model. This practical methodology gives access to a broad range of chiral spiro[indoline-3,4'-thiopyrano[2,3-b]indole] derivatives in good yields with excellent levels of enantioselectivities (up to 88% yield and 99% ee).

Synthesis of Indole-Fused Dihydrothiopyrano Scaffolds via (3 + 3)-Annulations of Donor-Acceptor Cyclopropanes with Indoline-2-Thiones

A new methodology for the synthesis of N-haloindole-fused dihydrothiopyrano derivatives via (3 + 3)-annulation of donor-acceptor cyclopropanes (DACs) with indoline-2-thiones in the presence of Sc(OTf)₃ as a Lewis acid catalyst has been developed. This protocol provides a variety of indole-fused dihydrothiopyrano molecules in good to excellent yields, which architecturally resemble other indole-fused tricyclic molecules having potential medicinal value. In addition, we have described a detailed reaction mechanism and transformation of the furnished product into N-fused thiazino indole molecule.

Recent development in asymmetric organocatalytic domino reactions involving 1,6-addition as a key step

This article highlights the significant development in stereoselective domino reactions involving 1,6-addition as a crucial step.

Asymmetric Dearomative Cascade Multiple Functionalizations of Activated N-Alkylpyridinium and N-Alkylquinolinium Salts

An enantioselective cascade reaction of N-alkylpyridinium and -quinolinium salts with o-hydroxybenzylideneacetones to access fused polyheterocycles through cross dienamine-mediated addition followed by trapping of the dearomatized enamine-type intermediates and aminal formation has been developed. A cascade assembly of N-benzyl-4-methylpyridinium salt and cyclic 2,4-dienones is further disclosed to give bridged frameworks via repetitive dearomatization and aromatization activation.

Synthesis of tetrahydrothiopyrano[2,3-b]indoles via [3+3] annulation of nitroallylic acetates with indoline-2-thiones

[3+3] annulation of 1,3-binucleophilic indolin-2-thione with 1,3-bielectrophilic nitroallylic acetate via an S_N2-reaction-6-endo-trig cyclization takes place with high regio- and stereoselectivity to afford tetrahydrothiopyranoindoles.

Domino 1,4- and 1,6-Addition Reactions of Ketene Silyl Acetals to Dialkynyl Imines Promoted by Aluminum Chloride: Synthesis of Multifunctionalized β-Lactams

Domino 1,4- and 1,6-addition reactions of ketene silyl acetals to dialkynyl imines are disclosed. Aluminum chloride promoted domino 1,4- and 1,6-addition reactions of ketene silyl acetals to dialkynyl imines to give a variety of alkenyl iminocyclobutenones in moderate to good yields. The chemoselective reduction of alkenyl iminocyclobutenones and the subsequent thermal rearrangement of resulting alkenyl aminocyclobutenones in the presence of appropriate amines provided cis or trans multifunctionalized β-lactams in moderate to high yields with good to high diastereoselectivities.

Organocatalytic asymmetric spirocyclization reactions of cyclic 2,4-dienones with cyanoketones: synthesis of spiro-dihydropyrano cyclohexanones

The first organocatalytic asymmetric synthesis of spiro-dihydropyrano cyclohexanones has been developed via the cascade reaction between cyanoketones and cyclic 2,4-dienones. A cinchona alkaloid-derived bifunctional primary amine catalyst in combination with N-Boc-tleucine was found to be the most effective for this spirocyclization reaction and provided the desired products in moderate to good yields with high enantioselectivities.

Facile synthesis of 9H-pyrrolo[1,2-a]indoles via Brønsted acid catalyzed cascade reactions

A Brønsted acid system promotes the Friedel–Crafts alkenylation/1,6-addition/condensation cascade reaction of ynones with indoles to access 9H-pyrrolo[1,2-a]indoles.

Brønsted-base-catalyzed remote cascade reactivity of 2,4-dienones - asymmetric synthesis of tetrahydrothiophenes

This study demonstrates that the remote cascade functionalization of 2,4-dienones can be realized by employing Brønsted base catalysis. The developed cascade involving 1,6-addition followed by the intramolecular aldol reaction provides a straightforward access to polysubstituted tetrahydrothiophene derivatives of biological and synthetic importance. Target products, bearing three contiguous stereocenters including one quaternary, have been obtained with excellent yields (up to 98%) and with good to high stereocontrol (>20 : 1 dr, up to 97 : 3 er) with the reaction cascade being promoted by a simple and readily available cinchona alkaloid cinchonine.

New development in the enantioselective synthesis of spiro compounds

In this review we summarize the latest developments in the enantioselective synthesis of spirocompounds. The most important organometallic and organocatalytic methodologies are highlighted.

Catalytic asymmetric synthesis of hetero-substituted oxindoles

The construction of chiral disubstituted oxindoles is an intriguing challenge for organic chemists.