Asymmetric Cycloaddition of N-2,2,2-Trifluoroethylisatin Ketimines and Unsymmetrical Dicarbonyl-Activated Alkenes: Construction of 5'-Trifluoromethylated 3,2'-Pyrrolidinyl Spirooxindoles with Three Carbonyl Groups

The asymmetric cycloaddition between N-2,2,2-trifluoroethylisatin ketimines and unsymmetrical dicarbonyl-activated alkenes catalyzed by a bifunctional squaramide has been discovered. The present study demonstrates an efficient approach for the regio-, diastereo-, and enantioselective synthesis of densely functionalized 5'-trifluoromethylated 3,2'-pyrrolidinyl spirooxindoles featuring three different types of carbonyl groups.

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

Synthesis of functionalized 3,2′-pyrrolidinyl spirooxindoles via domino 1,6-addition/annulation reactions of para-quinone methides and 3-chlorooxindoles

A highly efficient diastereoselective [4 + 1] cycloaddition of ortho-tosylaminophenyl-substituted p-QMs with 3-chlorooxindoles has been developed to afford 3,2′-pyrrolidinyl spirooxindoles.

Organocatalytic enantioselective SN1-type dehydrative nucleophilic substitution: access to bis(indolyl)methanes bearing quaternary carbon stereocenters

A highly general and straightforward approach to access chiral bis(indolyl)methanes (BIMs) bearing quaternary stereocenters has been realized via enantioconvergent dehydrative nucleophilic substitution. A broad range of 3,3'-, 3,2'- and 3,1'-BIMs were obtained under mild conditions with excellent efficiency and enantioselectivity (80 examples, up to 98% yield and >99 : 1 er). By utilizing racemic 3-indolyl tertiary alcohols as precursors of alkyl electrophiles and indoles as C-H nucleophiles, this organocatalytic strategy avoids pre-activation of substrates and produces water as the only by-product. Mechanistic studies suggest a formal SN1-type pathway enabled by chiral phosphoric acid catalysis. The practicability of the obtained enantioenriched BIMs was further demonstrated by versatile transformation and high antimicrobial activities (3al, MIC: 1 μg mL-1).

An update on the progress of cycloaddition reactions of 3-methyleneindolinones in the past decade: versatile approaches to spirooxindoles

Cycloaddition reactions are of great interest due to their potential and rapid construction of optically enriched spiro-cyclic products. 3-Methyleneindolinones have been proven to be a valuable precursor in cycloaddition reactions for the construction of diverse 3,3'-spirocyclic oxindoles. Their versatile reactivity has provided a new forum for the development of a variety of building blocks and synthetic compounds, including bioactive molecules. Herein, significant accomplishments in the cycloaddition reactions of 3-methyleneindolinones for the synthesis of spirooxindoles have been summarised and elaborated. The review is outlined according to the type of cycloaddition such as [2 + 1], [2 + 2], [3 + 2], [4 + 2] and [5 + 2] cycloaddition reactions.

Advances of α-activated cyclic isothiocyanate for the enantioselective construction of spirocycles

The efficient and enantioselective synthesis of pharmaceutically important spirocycles has attracted the focus of organic and medicinal chemists. In this context, with the excellent reactivity of α-activated isothiocyanate as formal 1,3-dipoles in the (3 + 2) cyclization process, the cyclic isothiocyanates featuring important pharmacophores, such as oxindole, pyrazolone, and indanone moieties, have emerged as powerful precursors to access a variety of spirocycles with highly structural diversities. In addition, the facile transformations of these spirocycles have shown potential applications in drug design. This review will cover the recent advances of α-activated cyclic isothiocyanates in the enantioselective construction of spirocycles since 2015, and the applications of corresponding products in organic and medicinal chemistry.

Stereoselective synthesis of trifluoroethyl 3,2'-spirooxindole γ-lactam through the organocatalytic cascade reaction of 3-((2,2,2-trifluoroethyl)amino)indolin-2-one

Newly designed 3-((2,2,2-trifluoroethyl)amino)indolin-2-ones were used for the facile synthesis of chiral fluoroalkyl-containing 3,2'-spirooxindole γ-lactam products. The secondary amine-catalysed Michael/hemiaminalization cascade reaction of 3-((2,2,2-trifluoroethyl)amino)indolin-2-one with α,β-unsaturated aldehydes followed by oxidation can easily produce the desired products in high yields (up to 86%) with excellent enantioselectivities (up to 99% ee) and diastereoselectivities (up to >95 : 5 dr).

Organocatalytic domino annulation of in situ generated tert-butyl 2-hydroxybenzylidenecarbamates with 2-isothiocyanato-1-indanones for synthesis of bridged and fused ring heterocycles

An asymmetric domino annulation of 2-isothiocyanato-1-indanones with tert-butyl 2-hydroxybenzylidenecarbamates was developed for the enantioselective construction of bridged and fused ring hererocycles in high yields with excellent stereoselectivities.

Stereoselective synthesis and applications of spirocyclic oxindoles

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

Double Spirocyclization of Arylidene-Δ2-Pyrrolin-4-Ones with 3-Isothiocyanato Oxindoles

Arylidene-Δ2-pyrrolin-4-ones undergo organocatalyzed double spirocyclization with 3-isothiocianato oxindoles in a domino 1,4/1,2-addition sequence. The products contain three contiguous stereocenters (ee up to 98%, dr up to 99:1, 12 examples). The absolute configuration of the major diastereomer was determined by single crystal X-ray analysis. Along with heterocyclic Michael acceptors based on oxazolone, isoxazolone, thiazolidinone, pyrazolone, and pyrimidinedione, the reported results display the applicability of unsaturated Δ2-pyrrolin-4-ones (pyrrolones) for the organocatalyzed construction of 3D-rich pyrrolone-containing heterocycles.

Enantioselective Dehydrative γ-Arylation of α-Indolyl Propargylic Alcohols with Phenols: Access to Chiral Tetrasubstituted Allenes and Naphthopyrans

Herein, we report an enantioselective dehydrative γ-arylation of α-indolyl propargylic alcohols with phenols via organocatalysis, which provides efficient access to chiral tetrasubstituted allenes and naphthopyrans in high yields with excellent regio- and enantioselectivities under mild conditions. This method features the use of cheaply available naphthols/phenols as the C-H aryl source and liberating water as the sole byproduct. Control experiments suggest that the excellent enantioselectivity and remote regioselectivity stem from dual hydrogen-bonding interaction with the chiral phosphoric acid catalyst.

Organocatalytic synthesis of chiral CF3-containing oxazolidines and 1,2-amino alcohols: asymmetric oxa-1,3-dipolar cycloaddition of trifluoroethylamine-derived azomethine ylides

A series of CF₃-containing oxazolidines were constructed via organocatalytic asymmetric oxa-1,3-dipolar cycloaddition. These oxazolidines could undergo facile conversion to CF₃-containing 1,2-amino alcohols with vicinal stereogenic centers.

Stereocontrolled [3+2] Cycloaddition of Donor-Acceptor Cyclopropanes to Iminooxindoles: Access to Spiro[oxindole-3,2'-pyrrolidines]

A novel stereocontrolled assembly of spiro[oxindole-3,2'-pyrrolidines] via [3+2]-cycloaddition of donor-acceptor cyclopropanes to electron-poor ketimines, iminooxindoles, was developed. The method allows for efficient employment of common readily available donor-acceptor cyclopropanes, functionalized with ester, keto, nitro, cyano etc. groups, and N-unprotected iminooxindoles. The stereospecificity of the initial S_N2-like imine attack on a cyclopropane molecule together with a high diastereoselectivity of further C-C bond formation facilitate a rapid access to spiro[oxindole-3,2'-pyrrolidines] in their optically active forms. Preliminary in vitro testing of the synthesized compounds against LNCaP (p53+) and PC-3 (p53-) cells revealed good antiproliferative activities and p53-selectivity indices for several compounds that are intriguing in terms of their further investigation as inhibitors of MDM2-p53 interaction.

Creation of bispiro[pyrazolone-3,3′-oxindoles] via a phosphine-catalyzed enantioselective [3 + 2] annulation of the Morita–Baylis–Hillman carbonates with pyrazoloneyldiene oxindoles

A [3 + 2] annulation between the Morita–Baylis–Hillman (MBH) carbonates and pyrazoloneyldiene oxindoles catalyzed by (S)-SITCP has been developed.

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.