ChiralN,N′-Dioxide-Organocatalyzed Regio-, Diastereo- and Enantioselective Michael Addition-Alkylation Reaction

Bipyridine-N,N'-dioxides Catalysts: Design, Synthesis, and Application in Asymmetric Synthesis of 1H-Pyrazolo[3,4-b]pyridine Analogues

A novel type of highly efficient chiral C2-symmetric bipyridine-N,N'-dioxides ligand application in catalyzing Michael addition/Cyclization of 5-aminopyrazoles with α,β-unsaturated 2-acyl imidazoles has been developed, affording the corresponding adducts in 85-97% yield with up to 99% enantioselectivity under mild conditions with a lower catalyst loading and broad scope. Remarkably, this protocol exhibits advantages in terms of reactivity and enantioselectivity, giving the fact that as low as 2.2 mol % of L1 and 2.0 mol % of Ni(OTf)2 can promote the title reaction on gram scale to afford the desired product with excellent enantioselectivity.

Synthesis of Chiral 2,3-Dihydrofurans via One-Pot Pd-Catalyzed Asymmetric Allylic Cycloaddition and a Retro-Dieckmann Fragmentation Cascade

An efficient method for the enantioselective synthesis of 2,3-dihydrofurans bearing a quaternary stereocenter has been developed via Pd-catalyzed asymmetric allylic cycloaddition and a retro-Dieckmann Fragmentation cascade. The asymmetric allylic cycloaddition of vinylethylene carbonates with 3-cyanochromone followed by base-assisted retro-Dieckmann fragmentation proceeded smoothly via a one-pot process to produce chiral 3,4-disubstituted 2,3-dihydrofurans in high yields with excellent enantioselectivities.

A mild one-pot synthesis of 2-iminothiazolines from thioureas and 1-bromo-1-nitroalkenes

A mild method to access functionalized 2-iminothiazolines in a facile and efficient manner has been developed. The reaction started from 1,3-disubstituted thioureas and 1-bromo-1-nitroalkenes in the presence of triethylamine in THF and proceeded smoothly in air to afford 2-iminothiazoline derivatives in moderate to good yields.

Stereoselective synthesis of 2-trifluoromethylated and 2-difluoromethylated dihydrofurans via organocatalytic cascade Michael/alkylation reaction

A highly stereoselective cascade Michael/alkylation process has been established to construct 2-trifluoromethylated and 2-difluoromethylated dihydrofurans.

Stereoselective Synthesis of Dihydrofuranoindoles via the Friedel-Crafts Alkylation/Annulation Cascade Process

A stereoselective annulation protocol was developed to construct dihydrofuranoindoles from readily available starting materials. In the presence of a bifunctional squaramide, the Friedel-Crafts alkylation/annulation cascade process occurred smoothly to provide dihydrofuranoindoles in 26-95% isolated yields exclusively as trans-diastereomers (38-99% ee). This catalytic protocol was compatible with a range of structurally distinct hydroxyindoles bearing the hydroxyl group at different positions, providing four kinds of dihydrofuranoindoles. Moreover, gram-scale synthesis and further synthetic manipulation of the product were also demonstrated.

Stereoselective synthesis of hydrazinodihydrofurans via cascade Michael addition-substitution involving the reaction of curcumin and other β-dicarbonyls with α-hydrazinonitroalkenes

Highly diastereoselective synthesis of 2-hydrazinated 2,3-dihydrofurans in good to excellent yields involving an interrupted Feist-Bénary type reaction by treating a wide variety of 1,3-dicarbonyl compounds, including curcumins, with α-hydrazinated nitroalkenes is reported here. The first ever enantioselective reaction of α-hydrazinonitroalkenes has also been carried out with two selected 1,3-dicarbonyls, dimedone and cyclohexanone by employing an l-t-leucine derived squaramide as the chiral organocatalyst to afford the enantio-enriched 2-hydrazinodihydrofurans as single diastereomers in good yields and with good enantioselectivities.

Enantioselective conjugate addition of an α,α-dithioacetonitrile with nitroalkenes using chiral bis(imidazoline)–Pd complexes

The first highly enantioselective reaction of α,α-dithioacetonitriles with nitroolefins as electron deficient olefins using chiral Phebim–Pd catalysts was developed.

Highly stereoselective synthesis of 2,3-dihydrofurans via a cascade Michael addition-alkylation process: a nitro group as the leaving group

The Michael addition-alkylation process between gem-benzoyl-nitrostyrenes and 1,3-dicarbonyl compounds proceeded smoothly in the presence of a bifunctional squaramide, exclusively providing 2,3-dihydrofurans as trans-diastereomers in 33-92% isolated yields and excellent enantioselectivities (29->99% ee).

Asymmetric synthesis of 3-aminodihydrocoumarins via the chiral guanidine catalyzed cascade reaction of azlactones

A new asymmetric preparative method of 3-aminodihydrocoumarins via reactions of azlactones and 2-nitrovinylphenols using chiral bifunctional guanidine catalysts.

Diastereodivergent asymmetric Michael-alkylation reactions using chiral N,N'-dioxide/metal complexes

A diastereodivergent asymmetric Michael-alkylation reaction between 3-chloro-oxindoles and β,γ-unsaturated-α-ketoesters has been achieved using L-RaPr₂ /Sc(OTf)₃ and L-PrPr₂ /Mg(OTf)₂ metal complexes as catalysts. Both rel-(1R,2S,3R) and rel-(1S,2S,3R) chiral spiro cyclopropane oxindoles were constructed in good yields, diastereoselectivities and ee values. The diastereodivergent control may originate from different alkylation pathways after the Michael addition, with either intramolecular trapping of the aza-ortho-xylylene intermediate or direct S_N2 substitution.