Asymmetric Construction of Spirooxindoles by Organocatalytic Multicomponent Reactions Using Diazooxindoles

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.

Metal-Free Geminal Difunctionalization of Diazocarbonyl Compounds: A One-Pot Multicomponent Strategy for the Construction of α,β-Diamino Carbonyl Derivatives

An unprecedented three-component domino oxidative coupling of diazocompounds for the efficient synthesis of α-azido-β-amino esters with non-activated dimethylamino compounds and simple TMSN₃ was achieved. The main features of this method include metal-free catalysis, satisfactory functional group tolerance, general applicability in complex molecule architectures, and excellent diastereoselectivity in the presence of chiral auxiliaries. In addition, several related control experiments have been conducted to investigate the reaction mechanism.

Efficient Catalytic Enantioselective Hydroxyamination of α-Aryl-α-Cyanoacetates with 2-Nitrosopyridines

The highly enantioselective totally N-selective hydroxyamination reaction of α-aryl-α-cyanoacetates with 2-nitrosopyridines was realized by using a chiral N,N'-dioxide/Mg(OTf)₂ complex as catalyst, which enriches the nitroso chemistry. A variety of 2-cyano-2-[hydroxyl(pyrydin-2-yl)amino]acetates with quaternary stereocenters and potential antibacterial activities were obtained in excellent yields with good to excellent ee values under as low as 0.05 mol % catalyst loading. The products could be easily transformed to useful α-amino amides and 1,2-diamines. Besides, a possible transition state model was proposed to elucidate the origin of the chirality induction.

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.