Organocatalytic Asymmetric Mannich Reaction of 3-Hydroxyoxindoles/3-Aminooxindoles with in Situ Generated N-Boc-Protected Aldimines for the Synthesis of Vicinal Oxindole–Diamines/Amino Alcohols

Enantioselective Construction of Vicinal Quaternary-Tetrasubstituted Carbon Stereocenters by Copper-Catalyzed Decarboxylative Propargylic Substitution

Enantioselective construction of vicinal tetrasubstituted carbon stereocenters is a formidable challenge in organic synthesis. A copper-catalyzed asymmetric decarboxylative propargylic substitution with 3-amino oxindoles as trisubstituted carbon nucleophiles and propargylic cyclic carbonates as tertiary carbon electrophiles was developed. A range of 3-amino-3,3'-disubstituted oxindoles bearing vicinal quaternary-tetrasubstituted carbon stereocenters were obtained in high yields and good to excellent stereoselectivities (up to 98% yield, >20:1 dr, and 98.5:1.5 er).

Synthesis of N-Boc-α-amino Acids from Carbon Dioxide by Electrochemical Carboxylation of N-Boc-α-aminosulfones

Electrochemical reduction of N-Boc-α-aminosulfones in DMF using an undivided cell equipped with a Pt plate cathode and an Mg rod anode under atmospheric pressure of bubbling carbon dioxide through the solution under constant current conditions resulted in a reductive C-S bond cleavage with elimination of benzenesulfinate ion generating the corresponding anion species followed by fixation of carbon dioxide to give the corresponding N-Boc-α-amino acids in moderate to good yields.

Box-copper catalyzed cascade asymmetric amidation for chiral exo-methylene aminoindoline derivatives

Enantioselective copper-catalyzed cascade inter- and intramolecular amidation was achieved between ethynyl benzoxazinanones and α-halohydroxamates in the presence of an indapybox ligand. The one-pot cascade transformation was triggered by the attack of hydroxamates to dipolar copper-allenylidene intermediates, followed by a nucleophilic annulation reaction. Thus, a series of exo-methylene 3-aminoindoline derivatives were obtained in good yields with high enantioselectivities under mild reaction conditions.

Tandem Photoredox-Chiral Phosphoric Acid Catalyzed Radical-Radical Cross-Coupling for Enantioselective Synthesis of 3-Hydroxyoxindoles

A photochemical protocol that couples diarylamines and α-ketoesters to afford the chiral 3-hydroxyoxindoles through tandem photoredox and chiral phosphoric acid catalysis is developed. The reaction involves an enantioselective photochemical radical-radical cross-coupling process. The chiral phosphoric acid is discovered to play crucial roles by decreasing the reductive potentials of α-ketoesters and stereocontrolling the downstream asymmetric radical-radical cross-coupling via the formation of pentacoordinate complex.

A zinc/PyBisulidine catalyzed asymmetric Mannich reaction of N-tosyl imines with 3-acyloxy-2-oxindoles

A Zn-PyBisulidine catalyzed asymmetric Mannich reaction of 3-acyloxy-2-oxindoles has been developed. Various quaternary substituted 3-acyloxy-2-oxindoles bearing vicinal amino alcohol motifs were obtained in good to excellent yields with moderate to excellent dr and excellent enantioselectivities. The utility of this reaction was demonstrated by the easy removal of the acyl group to give C3-hydroxy derivatives and their application as a key skeleton of the ligand for the Ni-catalyzed enantioselective Henry reaction.

Synergistic Ir/Cu Catalysis for Asymmetric Allylic Alkylation of Oxindoles: Enantio- and Diastereoselective Construction of Quaternary and Tertiary Stereocenters

3,3-Disubstituted oxindoles bearing quaternary and tertiary stereogenic centers are privileged structural motifs, which widely exist in pharmaceutical and natural products. Herein, a highly regio-, enantio-, and diastereoselective allylic alkylation of 3-alkyl oxindoles through synergistic iridium and copper catalysis is described, which provides a series of 3,3-disubstituted oxindole derivatives containing adjacent quaternary and tertiary stereogenic centers in excellent yields, enantiomeric excess, and diastereomeric ratio (for 30 examples, up to 97 % yield, >99 % ee, and >20 : 1 dr). This method provides exclusive branched selectivity, excellent enantio- and diastereoselectivities, and good functional compatibility. Control experiments suggested that the chiral copper catalyst is required for achieving high reactivities and diastereoselectivities under mild reaction conditions.

Asymmetric Synthesis of Oxindole-Derived Vicinal Tetrasubstituted Acyclic Amino Acid Derivatives by the Mannich-Type Reaction

The catalytic asymmetric Mannich-type reaction of 3-hydroxy/3-aminooxindoles with 2-aminoacrylates to afford oxindole-derived acyclic amino acid derivatives bearing vicinal tetrasubstituted stereocenters is reported. (DHQ)₂PHAL (4g) and quinine-derived squaramide (4d) were identified as efficient catalysts. Transformations of the Mannich-type reaction products highlight the utility of this synthetic strategy.

Organocatalytic Enantioselective Michael Addition between 3-(3-hydroxy-1H-pyrazol-1-yl)Oxindole and β-Nitrostyrene for the Preparation of Chiral Disubstituted Oxindoles

A new enantioselective Michael addition between 3-(3-hydroxy-1H-pyrazol-1-yl)oxindole, a new synthon generated from isatin N,N'-cyclic azomethine imine 1,3-dipole, and β-nitrostyrene has been disclosed. A series of chiral 3-(3-oxo-2,3-dihydro-1H-pyrazol-1-yl) disubstituted oxindoles were obtained in excellent results (up to 97% yield, up to 94% ee) with moderate to good diastereoselectivities (up to 4.3:1 dr).

A One-Pot Ring-Opening/Ring-Closure Sequence for the Synthesis of Polycyclic Spirooxindoles

One-pot ring-opening/ring-closure process of combining methyleneindolinone with 3-aminooxindole has been developed in this work. Novel polycyclic spirooxindoles were efficiently assembled under mild conditions in high yields (up to 95 %) with moderate to good diastereoselectivities (up to >95:5 d.r.) through simple filtration.

Recent synthetic applications of α-amido sulfones as precursors of N-acylimino derivatives

α-Amido sulfones can be directly used as N-acylimine or N-acyliminium ion precursors in several synthetic processes aimed at the preparation of nitrogen containing compounds. This review collects the most relevant and practical utilizations of α-amido sulfones appeared in the literature after 2005.

Copper-catalyzed enantioselective Mannich reaction between N-acylpyrazoles and isatin-derived ketimines

A copper-catalyzed enantioselective Mannich reaction between N-acylpyrazoles and isatin-derived ketimines is developed.

Asymmetric Mannich Reaction and Construction of Axially Chiral Sulfone-Containing Styrenes in One Pot from α-Amido Sulfones Based on the Waste-Reuse Strategy

A simultaneous asymmetric Mannich reaction and the construction of axially chiral sulfone-containing styrenes in one pot from α-amido sulfones based on the waste-reuse strategy was demonstrated. A series of chiral β-amino diesters and axially chiral sulfone-containing styrenes with various functional groups were synthesized in good to excellent yields and enantioselectivities under mild conditions. In addition, this protocol has been successfully applied to synthesize the anti-HIV drug Maraviroc and chiral trichloro derivatives.

An organocatalytic asymmetric Mannich reaction for the synthesis of 3,3-disubstituted-3,4-dihydro-2-quinolones

The first organocatalytic asymmetric Mannich reaction employing 3,4-dihydro-2-quinolones has been developed for the synthesis of biologically important 3,3-disubstituted-dihydro-2-quinolones. N-Boc imine precursor amidosulfones as well as pre-formed N-Boc imine were used for this purpose. Cyclohexyldiamine derived bifunctional amino-thiourea catalysts were employed to provide the products in high enantio- and good diastereoselectivities.

Organocatalytic Michael/cyclization cascade reactions of 3-isothiocyanato oxindoles with 3-trifluoroethylidene oxindoles: an approach for the synthesis of 3′-trifluoromethyl substituted 3,2′-pyrrolidinyl-bispirooxindoles

A series of 3′-trifluoromethyl substituted 3,2′-pyrrolidinyl-bispirooxindoles were constructed via an asymmetric Michael/cyclization cascade reaction.

DMAP-catalyzed alkylation of isatin N,N′-cyclic azomethine imine 1,3-dipoles with Morita–Baylis–Hillman carbonates

Metal-free C(sp³)–H alkylation of an isatin N,N′-cyclic azomethine imine 1,3-dipole.

Stereoselective Synthesis of 3,3'-Bisindolines by Organocatalytic Michael Additions of Fluorooxindole Enolates to Isatylidene Malononitriles in Aqueous Solution

A highly diastereoselective organocatalytic reaction for the synthesis of fluorinated 3,3'-bisindolines exhibiting adjacent tetrasubstituted carbon stereocenters is described. A broad variety of heterochiral bisindolines was prepared in 91-99% yield using 3-fluorooxindoles and isatylidene malononitriles in the presence of catalytic amounts of triethylamine in water or aqueous solution. The reaction can be upscaled without compromising yield and diastereoselectivity and the general usefulness of this method was demonstrated with various Michael acceptors and extended to aldol and Mannich reactions.

A DBU-catalyzed Michael–Pinner–isomerization cascade reaction of 3-hydroxyoxindoles with isatylidene malononitriles: access to highly functionalized bispirooxindoles containing a fully substituted dihydrofuran motif

The first DBU-catalyzed Michael/Pinner/isomerization cascade reaction of 3-hydrooxindoles with isatylidene malononitriles was developed.

Catalytic Enantioselective and Diastereoselective Allylic Alkylation with Fluoroenolates: Efficient Access to C3-Fluorinated and All-Carbon Quaternary Oxindoles

Synthetically versatile 3,3-disubstituted fluorooxindoles exhibiting vicinal chirality centers were obtained in high yields and with excellent enantio-, diastereo-, and regioselectivity through catalytic asymmetric fluoroenolate alkylation with allylic acetates. The reaction proceeds under mild conditions and can be scaled up without compromising the asymmetric induction. The unique synthetic usefulness of the products is highlighted by the incorporation of additional functionalities and the formation of 3-fluorinated oxindoles exhibiting an array of four adjacent centers of chirality. A new C-F bond functionalization path that provides unprecedented possibilities for the stereoselective generation of a chiral quaternary carbon center in the alkaloid scaffold is introduced.