Asymmetric catalytic multicomponent cascade reactions have become indispensable tools for enantioselective construction of spirooxindoles. In recent years, a number of successful strategies have been developed for the synthesis of enantioenriched spirooxindoles in high yield with excellent stereo- and regioselectivity. This review summarizes the recent advances on enantioselective construction of spirooxindoles including spiro[N-heterocycle-oxindoles], spiro[cycloalkane-oxindoles] and spiro[O-heterocycle-oxindoles] catalyzed by chiral phosphoric acids, amines, and bifunctional thiourea/squaramides.

Recent advances in organocatalytic asymmetric multicomponent cascade reactions for enantioselective synthesis of spirooxindoles

Azetidines represent one of the most important four-membered heterocycles used in organic synthesis and medicinal chemistry. The reactivity of azetidines is driven by a considerable ring strain, while at the same the ring is significantly more stable than that of related aziridines, which translates into both facile handling and unique reactivity that can be triggered under appropriate reaction conditions. Recently, remarkable advances in the chemistry and reactivity of azetidines have been reported. In this review, we provide an overview of the synthesis, reactivity and application of azetidines that have been published in the last years with a focus on the most recent advances, trends and future directions. The review is organized by the methods of synthesis of azetidines and the reaction type used for functionalization of azetidines. Finally, recent examples of using azetidines as motifs in drug discovery, polymerization and chiral templates are discussed.

Recent advances in the synthesis and reactivity of azetidines: strain-driven character of the four-membered heterocycle

The spirooxindole unit is one of the most widely investigated compound skeletons existing in numerous natural and pharmaceutical molecules. Thus, a large number of synthetic methodologies have already been reported to construct such a core structure. The trifluoromethyl group is another privileged unit in organic chemistry. The introduction of a CF3 group to an organic framework can significantly improve the properties of the molecule. In this context, an efficient approach for the construction of trifluoromethyl-containing spirooxindoles becomes a promising research direction among communities of industry and academia. In this Minireview, recent advances in the construction of trifluoromethyl-containing spirooxindoles have been summarized and discussed. In addition, representative synthetic methodologies and the corresponding reaction mechanisms have been described as well.

Recent Advances in the Construction of Trifluoromethyl‐Containing Spirooxindoles through Cycloaddition Reactions

Recent Advances in Squaramide-Catalyzed Asymmetric Mannich Reactions

Stereoselective Synthesis of CF 3 -Containing Spirooxindoles via 1,3-Dipolar Cycloaddition by Dipeptide-Based Phosphonium Salt Catalysis

A highly enantioselective [3 + 2] cycloaddition between 2,3-dioxopyrrolidines and N-2,2,2-trifluoroethylisatin ketimines with a quinine-derived squaramide catalyst in a diastereodivergence way has been described, which leads to two diastereomeric enantioenriched bispiro[oxindole-bi-pyrrolidine]s (incorporating CF3 units) with four consecutive stereocenters, including two adjacent spiro-quaternary centers. The reaction afforded the corresponding adducts in good to excellent yields with good to excellent enantioselectivities.

Diastereodivergent construction of bispiro[oxindole-bi-pyrrolidine]s with four consecutive stereocenters via asymmetric [3 + 2] cycloaddition of 2,3-dioxopyrrolidines using identical catalysts

Fluorination using chiral catalytic methods could result in a direct access to asymmetric fluorine chemistry. However, challenges in catalytic asymmetric fluorinations, especially the longstanding stereochemical challenges existed in BF3·Et2O-based fluorinations, have not yet been addressed. Here we report the catalytic asymmetric nucleophilic fluorination using BF3·Et2O as the fluorine reagent in the presence of chiral iodine catalyst. Various chiral fluorinated oxazine products were obtained with good to excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >20:1 dr). Control experiments (the desired fluoro-oxazines could not be obtained when Py·HF or Et3N·3HF were employed as the fluorine source) indicated that BF3·Et2O acted not only as a fluorine reagent but also as the activating reagent for activation of iodosylbenzene.

/pdf/catalytic-asymmetric-nucleophilic-fluorination-using-bf-3-et-vlld9vai1u.pdf

Catalytic asymmetric nucleophilic fluorination using BF 3 .Et 2 O as fluorine source and activating reagent

Herein, we have presented a facile and efficient method of ring-opening nucleophilic fluorination of aziridines, affording highly regio-selective β-fluorinated amines. Firstly, the example of ring-opening hydrofluorination of azetidines was reported. Then, the Olah's reagent also provided a promising method for the construction of enantioenriched β-fluoro-α-amino acid derivatives, which could be used for the preparation of peptide-based bioactive molecules.

Highly efficient regio-selective ring-opening nucleophilic fluorination of aziridines and azetidines: access to β- or γ-fluorinated amino acid derivatives.

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Diastereodivergent construction of bispiro[oxindole-bi-pyrrolidine]s with four consecutive stereocenters via asymmetric [3 + 2] cycloaddition of 2,3-dioxopyrrolidines using identical catalysts

Catalytic asymmetric nucleophilic fluorination using BF 3 .Et 2 O as fluorine source and activating reagent

Highly efficient regio-selective ring-opening nucleophilic fluorination of aziridines and azetidines: access to β- or γ-fluorinated amino acid derivatives.