Organocatalytic Asymmetric Michael/Friedel–Crafts Cascade Reaction of 3-Pyrrolyl-oxindoles and α,β-Unsaturated Aldehydes for the Construction of Chiral Spiro[5,6-dihydropyrido[1,2-a]pyrrole-3,3′-oxindoles]

Stereocontrolled Construction of Spirooxindole-Containing 5,6,7,8-Tetrahydropyrrolo[1,2-a]pyridine via Michael/Friedel-Crafts Domino Reaction Promoted by Secondary Amine-Squaramide

An asymmetric Michael/Friedel-Crafts cascade reaction with Morita-Baylis-Hillman (MBH) nitroallylic esters and 3-pyrrolyloxindoles has been developed for the stereoselective construction of spirooxindole-containing tetrahydroindolizines. A range of tetracyclic scaffolds possessing three consecutive chiral centers, including an all-carbon quaternary stereocenter, were generated in 53-85% isolated yields with high diastereoselectivities and enantiopurities (≥3:1 dr, 50-98% ee). A newly synthesized bifunctional secondary amine/squaramide organocatalyst was demonstrated to exhibit better stereochemical control than their tertiary analogues.

Sequential organo and metal catalyzed reaction between 3-pyrrolyloxindoles and linear nitroenynes: access to cyclic aza-spirooxindoles

An asymmetric Michael addition/hydroarylation reaction sequence, catalyzed by a sequential catalytic system consisting of a squaramide and a combination of silver and gold salts, provides a new series of cyclic aza-spirooxindole derivatives in excellent yields (up to 94%) and high diastero- and enantioselectivities (up to 7 : 1 dr, up to >99% ee). Computational study has also been performed.

Access to Spirooxindole-Fused Cyclopentanes via a Stereoselective Organocascade Reaction Using Bifunctional Catalysis

The present study reports an asymmetric organocascade reaction of oxindole-derived alkenes with 3-bromo-1-nitropropane efficiently catalyzed by the bifunctional catalyst. Spirooxindole-fused cyclopentanes were produced in moderate-to-good isolated yields (15-69%) with excellent stereochemical outcomes. The synthetic utility of the protocol was exemplified on a set of additional transformations of the corresponding spirooxindole compounds.

Stereoselective Domino Reactions in the Synthesis of Spiro Compounds

This review summarizes the latest developments in asymmetric domino reactions, with the emphasis on the preparation of spiro compounds. Discussions on the stereoselectivity of the transformations, the reaction mechanisms, the rationalization of the stereochemical outcome, and the applications of domino reactions to the synthesis of biologically active molecules and natural products are included when appropriate.

1 Introduction

2 Asymmetric Domino Reactions

2.1 Domino Reactions Initiated by Michael Reactions

2.2 Domino Reactions Initiated by Mannich Reactions

2.3 Domino Reactions Initiated by Knoevenagel Reactions

2.4 Domino Reactions Initiated by Cycloaddition Reactions

2.5 Domino Reactions Initiated by Metal Insertion

2.6 Other Mechanisms

3 Conclusion

Recent synthetic strategies toward the synthesis of spirocyclic compounds comprising six-membered carbocyclic/heterocyclic ring systems

Spirocyclic compounds fascinate the synthetic chemists due to their privileged ring system and efficacy in drug discovery. Many natural compounds comprise spirocyclic moiety in their skeleton and are effective in pharmaceutical industry. Over the years, many synthetic methodologies have been established for the construction of spirocyclic compounds. In this review, recent synthetic approaches to accessing various spirocompounds comprising six-membered carbocycles/heterocycles have been summarized.

Expedient Synthesis and Antibacterial Activity of Tetrahydro-1′H-spiro[indoline-3,4′-quinoline]-3′-carbonitrile Derivatives Using Piperidine as Catalyst

A convenient synthesis of 2′-amino-7′,7′-dimethyl-2,5′-dioxo-1′-(phenylamino)-5′,6′,7′,8′-tetrahydro-1′H-spiro[indoline-3,4′-quinoline]-3′-carbonitrile derivatives has been designed using different substituted isatins, various 5,5-dimethyl-3-(2-phenylhydrazinyl)cyclohex-2-enones (arylhydrazones of dimedone) and malononitrile in ethanol with piperidine as catalyst at room temperature. The structures of the synthesized compounds have been elucidated by various spectroscopic techniques. The selected compounds have also been evaluated for their antibacterial activities against human pathogenic bacteria.

Organocatalytic Asymmetric Synthesis of Aza-Spirooxindoles via Michael/Friedel-Crafts Cascade Reaction of 1,3-Nitroenynes and 3-Pyrrolyloxindoles

An asymmetric [3+3] cyclization of nitroenynes and 3-pyrrolyloxindoles has been realized with a chiral bifunctional squaramide catalyst. This Michael/Friedel-Crafts cascade strategy provides a facile and efficient access to enantioenriched polycyclic aza-spirooxindoles with 32-95% isolated yields and excellent stereocontrol under mild reaction conditions.

Stereoselective synthesis and applications of spirocyclic oxindoles

This review summaries recent synthetic developments towards spirocyclic oxindoles and applications as valuable medicinal and synthetic targets.

Copper-catalyzed regioselective [3+2] annulation of malonate-tethered acyl oximes with isatins

A copper-catalyzed regioselective [3+2] annulation of malonate-tethered acyl oximes with isatins was developed, affording valuable 2,3-dihydrooxazole-spirooxindoles in moderate to good yields with excellent diastereoselectivity.

Divergent synthesis of oxindole derivatives via controllable reactions of isatin-derived para-quinone methides with sulfur ylides

A catalyst-free and controllable reaction of isatin-derived para-quinone methides with sulfur ylides was developed, and it enables the divergent synthesis of two valuable oxindoles.

Enantioselective and regioselective aza-Friedel–Crafts reaction of electron-rich phenols with isatin-derived ketimines

An efficient asymmetric aza-Friedel–Crafts reaction of phenols with isatin-derived ketimines is described.

Titanocene(III)-Mediated 5-exo-trig Radical Cyclization: En Route to Spirooxindole-Based Tetrahydrofuran and Bicyclic Lactone

The isatin core system is of immense importance due to the highly reactive prochiral C-3 position, which paves an easy way to construct large arrays of spirooxindole heterocyclic motifs. Herein, we depict an isatin-derived and 3,3'-disubstituted oxindole-appended epoxy-acrylate undergoing Cp₂Ti(III)Cl-mediated reductive oxirane-ring opening with concomitant intramolecular 5-exo-trig radical cyclization leading to tetrahydrofuran-based oxa-spirooxindole systems. The fused spirooxindole structural feature is embedded in many natural products and tends to exhibit a wide spectrum of biological activities. The presence of more than one quaternary center and the availability of multiple functional groups like hydroxyl, ester, or lactone in the resultant products expand the scope of synthetic applications of the newly acquired oxa-spirooxindole molecules.

Tandem Organocatalytic Cycloaromatization/Intramolecular Friedel-Crafts Alkylation Sequence for the Synthesis of Indolizinones and Pyrrolo-azepinone Derivatives

The organocatalytic synthesis of indolizinones and pyrrolo-azepinones has been accomplished in a tandem fashion through a sequence that comprises initial cycloaromatization followed by intramolecular Friedel-Crafts alkylation. The process takes place under Brønsted acid catalysis, giving rise to final products in moderate to good yields. Attempts to carry out the tandem protocol in an enantioselective fashion were performed with chiral (R)-BINOL-derived N-triflyl phosphoramides. After initial optimization, the tandem process took place with moderate levels of enantioselectivity.

One-Pot Synthesis of Enantiopure Spiro[3,4-dihydrobenzo[b][1,4]oxazine-2,3'-oxindole] via Regio- and Stereoselective Tandem Ring Opening/Cyclization of Spiroaziridine Oxindoles with Bromophenols

A highly efficient regio- and stereoselective spiroaziridine ring opening with 2-bromophenols and a subsequent tandem cyclization reaction was developed for the one-pot synthesis of enantiopure 3,4-dihydrospiro[benzo[b][1,4]oxazine-2,3'-oxindole] with excellent enantiopurity (ee up to >99%). It is further extended to asymmetric synthesis of NH-free 3,4-dihydrospiro[benzo[b][1,4]oxazine-2,3'-xindole] retaining the optical activity.

An unexpected cascade reaction of 3-hydroxyoxindoles with coumarin-3-carboxylates to construct 2,3-dihydrobenzofuran spirooxindoles

An unexpected Michael addition-inspired ring-opening/closure cascade reaction of 3-hydroxyoxindoles with coumarin-3-carboxylates was developed.

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.

Diastereodivergent synthesis of bispirooxindoles via asymmetric Friedel–Crafts/aldol cascade reaction: co-catalyst effects on diastereoselective outcomes

The metal- and organo-catalyzed Friedel–Crafts/aldol cascade reaction has been developed to give diastereodivergent bispirooxindoles in high yields with excellent enantioselectivity.

Catalytic asymmetric synthesis of spirooxindoles: recent developments

The past four years have witnessed significant developments in the field of the catalytic asymmetric synthesis of spirooxindoles, and this feature article outlines the recent progress in this area, including the contributions of our group. This article is divided into sections according to the size and type of the generated spiro-ring fused at the C3-position of the oxindole core.

Organo-Catalyzed Asymmetric Michael-Hemiketalization-Oxa-Pictet-Spengler Cyclization for Bridged and Spiro Heterocyclic Skeletons: Oxocarbenium Ion as a Key Intermediate

A Michael-hemiketalization-oxa-Pictet-Spengler cyclization has been developed for the construction of chiral bridged and spiro heterocyclic skeletons with one spiro stereogenic carbon center and two bridgehead carbon centers, utilizing cooperative catalysts of a Takemoto thiourea catalyst and a triflimide. In particular, an oxocarbenium ion acts as a key intermediate for this cyclization reaction. Additionally, biological evaluation of this type of novel structure has revealed obvious antiproliferative activity against some cancer cell lines.

The organocatalytic asymmetric Neber reaction for the enantioselective synthesis of spirooxindole 2H-azirines

The catalytic asymmetric Neber reaction of 3-O-sulfonyl ketoxime for the synthesis of chiral spirooxindole 2H-azirines by using (DHQD)₂PHAL is reported.

An unprecedented protocol for the synthesis of 3-hydroxy-3-phenacyloxindole derivatives with indolin-2-ones and α-substituted ketones

A reaction between indolin-2-ones and α-substituted ketones was developed and a wide range of 3-hydroxy-3-phenacyloxindoles were obtained in good yield.

Enantioselective synthesis of chiral α,β-unsaturated γ-substituted butyrolactams by organocatalyzed direct asymmetric vinylogous Michael addition of α,β-unsaturated γ-butyrolactam to 2-enoylpyridines

Approach providing a series of optically active α,β-unsaturated γ-substituted butyrolactams in high yields with excellent diastereo- and enantioselectivities.

Diastereo- and enantioselective direct vinylogous Michael addition of γ-substituted butenolides to 2-enoylpyridines catalyzed by chiral bifunctional amine-squaramides

The enantioselective vinylogous Michael addition of γ-substituted butenolides to 2-enoylpyridines was developed to yield γ,γ-disubstituted butenolide derivatives in excellent stereoselectivities.