Kinetic Resolution of Aziridines via Catalytic Asymmetric Ring-Opening Reaction with Mercaptobenzothiazoles

Water-Mediated Radical Kinetic Resolution of Terminal Activated N-Carbamate Aziridines

Optically active terminal aziridines are fundamental building blocks for constructing complex nitrogen-containing molecules. Notably, the protecting group on the amino moiety critically governs not only the reactivity and enantioselectivity during aziridine formation but also the efficiency of downstream functionalization. While carbamates are among the most widely employed protecting groups in amine-related synthesis due to their versatility and orthogonality, their enantioselective incorporation into aziridines remains a long-standing challenge. Herein, we present the first radical approach for kinetic resolution of aziridines, enabling efficient access to a broad range of aziridines bearing diverse carbamate protecting groups and substituents. This transformation exploits the dual functionality of a dinuclear titanium radical catalyst, which enables enantiodiscriminative activation of racemic aziridines and coordinative activation of H2O as a sustainable hydrogen-atom donor. Mechanistic studies reveal that the optimal distribution of the catalyst between aziridine and H2O is crucial for sustaining the cooperative catalytic cycle.

Nickel-Catalyzed Cross-Coupling of Aziridines with Thioesters toward Atom-Economic Synthesis of β-Sulfanyl Amides

Thioesters have been recognized as a class of powerful bifunctional reagents, namely, great donors of acyl and sulfide moieties. However, such application in value-added synthesis is still very limited to date. Herein, a nickel-catalyzed cross-coupling reaction system of aziridines with thioesters was developed under redox-neutral and mild conditions. This catalytic method provides an atom-economic route for the synthesis of diverse β-sulfanyl amide derivatives with wide substrate scope (43 examples), good functional group tolerance, and regioselectivity.

Merging Ring-Opening 1,2-Metallate Shift with Asymmetric C(sp3)-H Borylation of Aziridines

Chiral secondary alkyl amines with a vicinal quaternary stereocenter are undoubtedly important and ubiquitous subunits in natural products and pharmaceuticals. However, their asymmetric synthesis remains a formidable challenge. Herein, we merge the ring-opening 1,2-metallate shift with iridium-catalyzed enantioselective C(sp3)-H borylation of aziridines to deliver these frameworks with high enantioselectivities. We also demonstrated the synthetic application by downstream transformations, including the total synthesis of two Amaryllidaceae alkaloids, (-)-crinane and (+)-mesmebrane.

Regioselective Brønsted acid catalyzed ring opening of aziridines by phenols and thiophenols; a gateway to access functionalized indolines, indoles, benzothiazines, dihydrobenzo-thiazines, benzo-oxazines and benzochromenes

Brønsted acid catalyzed regioselective ring opening of aziridines by phenols and thiophenols have been reported. Involvement of a series of aziridines with a range of phenols and thiophenols offer the generality of the reported protocol. Completion of the reaction at room temperature within very short time brings the uniqueness of the developed technique. To emphasis on the application of the developed methodology, the products have been used for the further synthesis of a range of useful and novel heterocyclic molecules such as indolines, indoles, benzothiazines, dihydrobenzothiazines, benzo-oxazines and benzochromenes.

Asymmetric Synthesis of Hydrodibenzofurans from Norcaradienes: Kinetic Resolution via [3 + 2] Cycloaddition with Quinones

The catalytic asymmetric [3 + 2] cycloaddition of racemic norcaradienes with quinones to construct multicyclic hydrodibenzofurans was achieved by the use of chiral N,N'-dioxide/metal complex catalysts. Kinetic resolution of norcaradienes accompanied by partial racemization occurred, and one enantiomer in prior acted as the C2 synthon to participate in diastereoselective cycloaddition. An enantiodivergent synthesis via a switch of metal ions was observed when naphthoquinone was used as the partner. DFT calculations revealed the profiles of the cycloaddition processes.

Catalytic asymmetric addition of thiols to silyl glyoxylates for synthesis of multi-hetero-atom substituted carbon stereocenters

A chiral Lewis acid-catalyzed enantioselective addition of thiols to silyl glyoxylates was developed. The reaction proceeds well with a broad range of thiols and acylsilanes, affording the target tertiary chiral α-silyl–α-sulfydryl alcohols with multi-hetero-atom carbon stereocenters in excellent yields (up to 99%) and enantioselectivities (up to 98% ee). A series of control experiments were conducted to elucidate the reaction mechanism.

Enantioselective addition of thiols to silyl glyoxylates for construction of a multi-hetero-atom substituted carbon stereocenter was described.

An Organocatalytic Kinetic Resolution of Aziridines by Thiol Nucleophiles

We report the first organocatalytic kinetic resolution of unactivated aziridines by sulfur nucleophiles with excellent enantioselectivity. A suitable chiral phosphoric acid was found to catalyze the intermolecular ring opening under mild conditions, furnishing a range of highly enantioenriched β-amino thioethers and aziridines, both of which are useful synthetic building blocks.