Highly Enantioselective Construction of 3-Hydroxy Oxindoles through a Decarboxylative Aldol Addition of Trifluoromethyl α-Fluorinatedgem-Diols toN-Benzyl Isatins

Merging Electrosynthesis and Bifunctional Squaramide Catalysis in the Asymmetric Detrifluoroacetylative Alkylation Reactions

An enantioselective bifunctional squaramide-catalyzed detrifluoroacetylative alkylation reaction has been developed under electrochemical conditions. The unified strategy based on this key tandem methodology has been divergently explored for the asymmetric synthesis of fluorine-containing target molecules with good stereocontrol (up to 95 % ee). Furthermore, this asymmetric catalytic reaction combines the benefits of electrosynthesis and organocatalysis for the preparation of biologically relevant products containing C-F tertiary stereogenic centers.

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 Michael Addition Reactions of Tertiary Enolates Generated by Detrifluoroacetylation

This work describes, for the first time, Michael addition reactions of tertiary fluoro-enolates in situ generated by detrifluoroacetylation with 1-(1-(phenylsulfonyl) vinylsulfonyl)benzene. Excellent enantioselectivity and chemical yields were achieved with application of catalysts (10 mol %) derived from Cu(OTf)₂ and (1S,2S)-1,2-diphenylethane-1,2-diamine. These reactions show a considerable degree of structural generality and allow the preparation of new types of biologically relevant molecules that contain quaternary C-F stereogenic carbon atoms and feature five-, six-, or seven-membered rings as well as heterocyclic 3-fluoro-2,3-dihydrochromen-4-one moieties.

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.

Enantioselective Synthesis of Spirooxindole Enols: Regioselective and Asymmetric [3+2] Cyclization of 3-Isothiocyanato Oxindoles with Dibenzylidene Ketones

A novel cinchona-alkaloid-derived organocatalyst has been developed to catalyze the asymmetric regioselective [3+2] cycloaddition of 3-isothiocyanato oxindoles with dibenzylidene ketones. A series of spirooxindole enols could be obtained in high yields with good-to-excellent diastereo- and enantioselectivities.

Assembly of Fluorinated Quaternary Stereogenic Centers through Catalytic Enantioselective Detrifluoroacetylative Aldol Reactions

A Cu-catalyzed asymmetric detrifluoroacetylative aldol addition reaction of 2-fluoro-1,3-diketones/hydrates to aldehydes in the presence of base and chiral bidentate ligand was developed. The reaction was carried out under convenient conditions and tolerated a wide range of substrates, resulting in fluorinated quaternary stereogenic α-fluoro-β-hydroxy ketone products with good chemical yields, diastereo- and enantioselectivities. This catalytic asymmetric detrifluoroacetylative aldol addition reaction provides a new approach for the preparation of biologically relevant products containing C-F quaternary stereogenic centers.

Construction of chiral bridged tricyclic benzopyrans: enantioselective catalytic Diels-Alder reaction and a one-pot reduction/acid-catalyzed stereoselective cyclization

An asymmetric two-step approach to chiral bridged tricyclic benzopyrans, core structures featured in various natural products, is described. In the synthesis, an unprecedented enantioselective catalytic decarboxylative Diels-Alder reaction is developed using readily available coumarin-3-carboxylic acids and aldehydes as reactants under mild reaction conditions. Notably, the decarboxylation-assisted release of the catalyst enables the process to proceed efficiently with high enantio- and diastereoselectivity. Furthermore, a one-pot procedure for either a LiAlH4 - or NaBH4 -mediated reduction with subsequent acid-catalyzed intramolecular cyclization of the Diels-Alder adducts was identified for the efficient formation of the chiral bridged tricyclic benzopyrans.

Asymmetric Aldol Reaction of 3-Acetyl-2H-chromen-2-ones and Isatins Catalyzed by a Bifunctional Quinidine Urea Catalyst

The asymmetric aldol reaction of 3-acetyl-2H-chromen-2-ones and isatins has been realized by using a bifunctional quinidine-derived urea as the catalyst. The corresponding 3-hydroxyoxindole derivatives containing a 2H-chromen-2-one moiety were obtained in good yields and high enantioselectivities. When (Z)-ethyl 2-benzylideneacetoacetate was used as the substrate, a mixture of two diastereomers (both Z and E) was obtained due to the isomerization of the double bond under the reaction conditions.