Enantioselective Synthesis of 3-Alkynyl-3-hydroxyindolin-2-ones by Copper-Catalyzed Asymmetric Addition of Terminal Alkynes to Isatins

Modular synthesis of 3,3-disubstituted oxindoles from nitrones and acrylic acids

We developed a modular synthesis for 3,3-disubstituted oxindoles, utilising readily accessible nitrones and acrylic acids. This approach facilitates the preparation of a diverse array of oxindoles through the variation of the starting materials. We demonstrated the applicability of this method through a gram-scale reaction and a synthesis of esermethole.

Enantioselective synthesis of 3-hydroxy- and 3-amino-3-alkynyl-2-oxindoles by the dimethylzinc-mediated addition of terminal alkynes to isatins and isatin-derived ketimines

A common protocol for enantioselective alkynylation of isatins and isatin-derived ketimines using terminal alkynes and Me2Zn in the presence of a catalytic amount of a chiral perhydro-1,3-benzoxazine with moderate to excellent enantioselectivity under mild reaction conditions is described. The additions to ketimines present a novel approach to chiral amines being derivatives of oxindoles. The reaction is broad in scope with respect to aryl- and alkyl-substituted terminal alkynes and isatin derivatives. In isatins, the alkynylation occurs at the Si face of the carbonyl group, whereas in the ketimine derivatives it occurs at the Re face of the imine.

Chiral Quaternary Ammoniums Derived from Dehydroabietylamine: Synthesis and Application to Alkynylation of Isatin Derivatives Catalyzed by Silver

Abietic acid and its derivatives have broadly been used in fine chemicals and are renewable resources. Its inherent chiral rigid tricyclic phenanthrene skeleton is unique. Its utilities in asymmetric catalysis remain to be explored. A series new amide-type chiral quaternary ammoniums bearing dehydroabietylamine were designed, and prepared by two convenient steps. Acylation of dehydroabietylamine with bromoacetyl chloride afforded amide holding bromoacetyl group in higher yields using triethyl amine as base. Subsequent quaternization reaction gave the desired amide-type chiral quaternary ammoniums. The new chiral quaternary ammoniums can be used as phase-transfer catalyst (PTC) for the transition metal-catalysed alkynylation of isatin derivatives.

Reversal of Enantioselectivity in the Copper-Aminophenol Sulfonamide Catalyzed Alkynylation of Isatins by Slightly Tuning the Ligand Structure and Basic Additives

A series of new chiral aminophenol sulfonamide ligands with a monochiral arm has been developed for the first Cu(I) catalyzed enantiodivergent alkynylation of isatins. Dramatic reversal of enantioselectivity was accomplished by slightly tuning the substituted benzenesulfonamide and achiral basic additives. A wide range of both terminal alkynes and isatins are tolerated by this new catalyst system with up to 99% yield and 97% ee.

Dimethylzinc-mediated enantioselective addition of terminal alkynes to 1,2-diketones using perhydro-1,3-benzoxazines as ligands

A conformationally restricted perhydro-1,3-benzoxazine derived from (-)-8-aminomenthol behaves as a good chiral ligand in the dimethylzinc-mediated enantioselective monoaddition of aromatic and aliphatic terminal alkynes to 1,2-diketones. The corresponding α-hydroxyketones were obtained in good yields with high enantioselectivities starting from both aromatic and aliphatic 1,2-diketones. The alkynylation of unsymmetrical 1,2-diketones with electronically different substituents also proceeds with high regio- and enantioselectivity. This reaction provides a practical method to synthesize ketones bearing a chiral tertiary propargylic alcohol.

Syntheses of 2-Iminoindolin-3-ones and 2-Alknyl-2,3-dihydroquinazolin-4(1H)-ones from 3-Diazoindolin-2-imines

3-Diazoindolin-2-imines reacted with nitrones to furnish 2-iminoindolin-3-ones through a Au(I)-catalyzed cascade oxygen transfer/imine exchange process. The prepared 2-iminoindolin-3-ones could be further transformed into 2-alknyl-2,3-dihydroquinazolin-4(1H)-ones through a Ag(I)-catalyzed reaction with terminal alkynes. A MeOH-triggered ring expansion mechanism involving cyclic iminium formation and nucleophilic addition is proposed for this novel alkynylation reaction. This two-step procedure provides a general and convenient approach to 2-alknyl-2,3-dihydroquinazolin-4(1H)-ones, which are privileged structures in medicinal chemistry.

Enantioselective nickel-catalyzed arylative and alkenylative intramolecular 1,2-allylations of tethered allene-ketones

The enantioselective nickel-catalyzed reaction of tethered allene-ketones with (hetero)arylboronic acids or potassium vinyltrifluoroborate is described. Carbonickelation of the allene gives allylnickel species, which undergo cyclization by 1,2-allylation to produce chiral tertiary-alcohol-containing aza- and carbocycles in high diastereo- and enantioselectivities.

Catalytic Enantioselective Ynamide Additions to Isatins: Concise Access to Oxindole Alkaloids

The highly enantioselective addition of terminal ynamides to a variety of isatins, catalyzed by a bisoxazolidine copper complex under mild, base-free reaction conditions, is described. The reaction is broad in scope, scalable, applicable to unprotected isatins, and provides efficient access to 3-hydroxyoxindoles carrying a tetrasubstituted chiral center with excellent yields and enantioselectivities. Synthetically versatile, multifunctional 3-hydroxyindolinones are obtained by hydration, partial hydrogenation, or hydroxyacyloxylation of the ynamide moiety at room temperature and exhaustive hydrogenation followed by reductive detosylation and spontaneous cyclization affords cinchonamidine alkaloids.

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.

Copper-catalyzed enantioselective alkynylation of pyrazole-4,5-diones with terminal alkynes

A copper-catalyzed enantioselective alkynylation between pyrazole-4,5-diones and terminal alkynes is developed, and both enantiomers of chiral propargylic alcohols can be achieved by using the ligand illustrated and its diastereomer.

Copper powder-catalyzed chelation-assisted cascade reaction of o-chloroarylacetic acids with amines under solvent- and ligand-free conditions: synthesis of oxindoles

Copper powder-catalyzed sequential C–Cl amination/intramolecular N-acylation under solvent- and ligand-free conditions is developed to access oxindoles.

Dinuclear zinc complex catalyzed asymmetric methylation and alkynylation of aromatic aldehydes

A general AzePhenol dinuclear zinc catalytic system has been successfully developed and introduced into the asymmetric addition of dimethylzinc and alkynylzinc to aromatic aldehydes.