Highly Enantioselective Synthesis of Acyclic N,N′-Acetals by Chiral Urea Derived from Quinine Catalyzed the Addition of Aryl Amines to Isatin-Derived Ketimines

Cu-Catalyzed Direct Asymmetric Mannich Reaction of 2-Alkylazaarenes and Isatin-Derived Ketimines

The first direct catalytic asymmetric Mannich reaction of 2-alkylazaarenes and ketimines was realized with a chiral Cu-bis(oxazoline) complex as the catalyst. The asymmetric addition of 2-alkylpyridines to isatin-derived ketimines proceeded smoothly to afford α,β-functionalized 2-substituted pyridines bearing 3-amino-3,3-disubstituted oxindole motifs with excellent results (≤99% yield, 99:1 dr, and 98% ee). The catalytic system was also extended to 2-alkylbenzothiazoles as nucleophiles for the asymmetric Mannich reaction of ketimines.

Organocatalytic Asymmetric [4 + 2]-Cycloadditions of 2-Aminophenyl Enones with Isatin-Derived Ketimines: Diastereo- and Enantioselective Synthesis of Spirooxindole-Tetrahydroquinazolines

A novel method for the enantioselective synthesis of spiro N,N-heterocyclic oxindoles has been developed, employing asymmetric [4 + 2]-cycloadditions of 2-aminophenyl enones with isatin-derived ketimines. This method employs an organocatalytic approach, utilizing a bifunctional squaramide-based catalyst. It enables the precise synthesis of chiral spirooxindole-tetrahydroquinazolines with intricate structures, featuring chiral quaternary centers. This process achieves remarkable results, including high yields and exceptional levels of enantioselectivity and diastereoselectivity (up to 96% yield, 95% ee, and >20:1 dr).

Bifunctional phase-transfer catalysts for synthesis of 2-oxazolidinones from isocyanates and epoxides

A series of bifunctional phase-transfer catalysts (PTCs) were synthesized to catalyze the [3 + 2] coupling reaction of isocyanates and epoxides to afford 2-oxazolidinones in good to high yields (up to 92% yield) using PhCl as a solvent at 100 °C within 12 h. These bifunctional PTCs were easily prepared from commercially available tertiary-primary diamines and isocyanates (or isothiocyanates, mono-squaramides, respectively) in two simple steps with good modularity and demonstrated high efficiency (2.5 mol% catalyst-loading). The synergistic interaction of the quaternary ammonium salt center and hydrogen-bond donor group in the catalyst with the substrate is crucial to this atom-economic reaction.

Highly Chemo-, Site-, and Enantioseletive para C-H Aminoalkylation of N-Monosubstituted Aniline Derivatives Affording 3-Amino-2-oxindoles

In general, enantioselective C-H functionalization of N-monosubstituted anilines is a highly challenging task owing to the competitive chemoselective N-H bond insertion reactions. In this paper, we reported a direct highly chemo-, site-, and enantioselective para C-H aminoalkylation of N-monosubstituted aniline derivatives with isatin-derived ketimines in the presence of chiral phosphoric acids (CPAs) and offered a practical strategy for para asymmetric C-H functionalization of anilines containing N-H bonds.

Recent advances in the catalytic synthesis of 3-aminooxindoles: an update

3-Substituted-3-aminooxindoles are versatile scaffolds and these motifs constitute the core structure of number of natural products and biologically active compounds.

Enantioselective addition of thiols to trifluoromethyl ketimines: synthesis of N,S-ketals

Enantioselective addition of thiols to acyclic trifluoromethyl ketimines for the construction of trifluoromethylated N,S-ketals was performed successfully using a bifunctional squaramide catalyst.

Enantioselective construction of 3-substituted 3-amino-2-oxindoles containing an N,N-ketal skeleton via organocatalyzed aza-addition of isatin imines

The first example of organocatalytic chemo-, regio- and enantioselective aza-Mannich reactions of triazoles and arylamines, respectively, with isatin-derived imines has been achieved in the presence of double hydrogen bonding organocatalysts, affording the valuable optically active 3-substituted 3-amino-2-oxindoles featuring N,N-ketal structural motifs in high yields. This strategy was featured by low catalyst loading, mild conditions, broad substrate scope, and high efficiency and selectivity.